diff --git a/.eslintrc.json b/.eslintrc.json
index 9b7c229b..a4f08d68 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -11,6 +11,7 @@
     { "files": ["*.browser.js"], "env": { "browser": true } }
   ],
   "rules": {
+    "strict": ["error", "global"],
     "no-await-in-loop": "warn",
     "no-compare-neg-zero": "error",
     "no-extra-parens": ["warn", "all", {
diff --git a/src/WebSocket.js b/src/WebSocket.js
index c6f4209f..2a303cc4 100644
--- a/src/WebSocket.js
+++ b/src/WebSocket.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { browser } = require('./util/Constants');
 const querystring = require('querystring');
 try {
diff --git a/src/client/BaseClient.js b/src/client/BaseClient.js
index c9fce590..68621360 100644
--- a/src/client/BaseClient.js
+++ b/src/client/BaseClient.js
@@ -1,3 +1,5 @@
+'use strict';
+
 require('setimmediate');
 const EventEmitter = require('events');
 const RESTManager = require('../rest/RESTManager');
diff --git a/src/client/Client.js b/src/client/Client.js
index 5d5deddf..1bc8232b 100644
--- a/src/client/Client.js
+++ b/src/client/Client.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const BaseClient = require('./BaseClient');
 const Permissions = require('../util/Permissions');
 const ClientVoiceManager = require('./voice/ClientVoiceManager');
diff --git a/src/client/WebhookClient.js b/src/client/WebhookClient.js
index 0a848d80..94e17a71 100644
--- a/src/client/WebhookClient.js
+++ b/src/client/WebhookClient.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Webhook = require('../structures/Webhook');
 const BaseClient = require('./BaseClient');
 
diff --git a/src/client/actions/Action.js b/src/client/actions/Action.js
index 8fdadc92..791eaa00 100644
--- a/src/client/actions/Action.js
+++ b/src/client/actions/Action.js
@@ -1,3 +1,5 @@
+'use strict';
+
 /*
 
 ABOUT ACTIONS
diff --git a/src/client/actions/ActionsManager.js b/src/client/actions/ActionsManager.js
index f349b9bc..268e4371 100644
--- a/src/client/actions/ActionsManager.js
+++ b/src/client/actions/ActionsManager.js
@@ -1,3 +1,5 @@
+'use strict';
+
 class ActionsManager {
   constructor(client) {
     this.client = client;
diff --git a/src/client/actions/ChannelCreate.js b/src/client/actions/ChannelCreate.js
index 57b4e6df..4a9d17d4 100644
--- a/src/client/actions/ChannelCreate.js
+++ b/src/client/actions/ChannelCreate.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/actions/ChannelDelete.js b/src/client/actions/ChannelDelete.js
index 7f182e60..b9909f8b 100644
--- a/src/client/actions/ChannelDelete.js
+++ b/src/client/actions/ChannelDelete.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/actions/ChannelUpdate.js b/src/client/actions/ChannelUpdate.js
index ac2d4f69..b610ea7c 100644
--- a/src/client/actions/ChannelUpdate.js
+++ b/src/client/actions/ChannelUpdate.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 
 class ChannelUpdateAction extends Action {
diff --git a/src/client/actions/GuildBanRemove.js b/src/client/actions/GuildBanRemove.js
index 7d19c75b..62779137 100644
--- a/src/client/actions/GuildBanRemove.js
+++ b/src/client/actions/GuildBanRemove.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/actions/GuildChannelsPositionUpdate.js b/src/client/actions/GuildChannelsPositionUpdate.js
index 863d7dc5..b2111594 100644
--- a/src/client/actions/GuildChannelsPositionUpdate.js
+++ b/src/client/actions/GuildChannelsPositionUpdate.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 
 class GuildChannelsPositionUpdate extends Action {
diff --git a/src/client/actions/GuildDelete.js b/src/client/actions/GuildDelete.js
index 27ea1b00..7c61ebac 100644
--- a/src/client/actions/GuildDelete.js
+++ b/src/client/actions/GuildDelete.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/actions/GuildEmojiCreate.js b/src/client/actions/GuildEmojiCreate.js
index 121e89ab..379c62e0 100644
--- a/src/client/actions/GuildEmojiCreate.js
+++ b/src/client/actions/GuildEmojiCreate.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/actions/GuildEmojiDelete.js b/src/client/actions/GuildEmojiDelete.js
index 7b94ff41..d5c973af 100644
--- a/src/client/actions/GuildEmojiDelete.js
+++ b/src/client/actions/GuildEmojiDelete.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/actions/GuildEmojiUpdate.js b/src/client/actions/GuildEmojiUpdate.js
index 34e235a0..9fa59c96 100644
--- a/src/client/actions/GuildEmojiUpdate.js
+++ b/src/client/actions/GuildEmojiUpdate.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/actions/GuildEmojisUpdate.js b/src/client/actions/GuildEmojisUpdate.js
index aaa89847..d6902d53 100644
--- a/src/client/actions/GuildEmojisUpdate.js
+++ b/src/client/actions/GuildEmojisUpdate.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 
 class GuildEmojisUpdateAction extends Action {
diff --git a/src/client/actions/GuildIntegrationsUpdate.js b/src/client/actions/GuildIntegrationsUpdate.js
index 8bb6eabf..a8e91077 100644
--- a/src/client/actions/GuildIntegrationsUpdate.js
+++ b/src/client/actions/GuildIntegrationsUpdate.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/actions/GuildMemberRemove.js b/src/client/actions/GuildMemberRemove.js
index 62373e48..6a4ae397 100644
--- a/src/client/actions/GuildMemberRemove.js
+++ b/src/client/actions/GuildMemberRemove.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events, Status } = require('../../util/Constants');
 
diff --git a/src/client/actions/GuildRoleCreate.js b/src/client/actions/GuildRoleCreate.js
index e4657213..36111f06 100644
--- a/src/client/actions/GuildRoleCreate.js
+++ b/src/client/actions/GuildRoleCreate.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/actions/GuildRoleDelete.js b/src/client/actions/GuildRoleDelete.js
index 0cecc8ef..31b13b81 100644
--- a/src/client/actions/GuildRoleDelete.js
+++ b/src/client/actions/GuildRoleDelete.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/actions/GuildRoleUpdate.js b/src/client/actions/GuildRoleUpdate.js
index c2e082c7..bf61c787 100644
--- a/src/client/actions/GuildRoleUpdate.js
+++ b/src/client/actions/GuildRoleUpdate.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/actions/GuildRolesPositionUpdate.js b/src/client/actions/GuildRolesPositionUpdate.js
index af29702a..f09f1143 100644
--- a/src/client/actions/GuildRolesPositionUpdate.js
+++ b/src/client/actions/GuildRolesPositionUpdate.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 
 class GuildRolesPositionUpdate extends Action {
diff --git a/src/client/actions/GuildUpdate.js b/src/client/actions/GuildUpdate.js
index ac592d27..6d7cf9b4 100644
--- a/src/client/actions/GuildUpdate.js
+++ b/src/client/actions/GuildUpdate.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/actions/MessageCreate.js b/src/client/actions/MessageCreate.js
index e34eabc2..d4ef6400 100644
--- a/src/client/actions/MessageCreate.js
+++ b/src/client/actions/MessageCreate.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/actions/MessageDelete.js b/src/client/actions/MessageDelete.js
index cbe555e8..d66d10a2 100644
--- a/src/client/actions/MessageDelete.js
+++ b/src/client/actions/MessageDelete.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/actions/MessageDeleteBulk.js b/src/client/actions/MessageDeleteBulk.js
index ac8d9b39..53f4ba05 100644
--- a/src/client/actions/MessageDeleteBulk.js
+++ b/src/client/actions/MessageDeleteBulk.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const Collection = require('../../util/Collection');
 const { Events } = require('../../util/Constants');
diff --git a/src/client/actions/MessageReactionAdd.js b/src/client/actions/MessageReactionAdd.js
index 06b146df..a800c3c7 100644
--- a/src/client/actions/MessageReactionAdd.js
+++ b/src/client/actions/MessageReactionAdd.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 
 /*
diff --git a/src/client/actions/MessageReactionRemove.js b/src/client/actions/MessageReactionRemove.js
index af76c4fd..7ab5be28 100644
--- a/src/client/actions/MessageReactionRemove.js
+++ b/src/client/actions/MessageReactionRemove.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/actions/MessageReactionRemoveAll.js b/src/client/actions/MessageReactionRemoveAll.js
index ac03c6e8..f3273097 100644
--- a/src/client/actions/MessageReactionRemoveAll.js
+++ b/src/client/actions/MessageReactionRemoveAll.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/actions/MessageUpdate.js b/src/client/actions/MessageUpdate.js
index 4fbdce4e..be26b269 100644
--- a/src/client/actions/MessageUpdate.js
+++ b/src/client/actions/MessageUpdate.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 
 class MessageUpdateAction extends Action {
diff --git a/src/client/actions/PresenceUpdate.js b/src/client/actions/PresenceUpdate.js
index 538e0e8a..649bf6ce 100644
--- a/src/client/actions/PresenceUpdate.js
+++ b/src/client/actions/PresenceUpdate.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/actions/UserUpdate.js b/src/client/actions/UserUpdate.js
index 3ff40790..a762511f 100644
--- a/src/client/actions/UserUpdate.js
+++ b/src/client/actions/UserUpdate.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/actions/VoiceStateUpdate.js b/src/client/actions/VoiceStateUpdate.js
index 80e120cb..e4efa129 100644
--- a/src/client/actions/VoiceStateUpdate.js
+++ b/src/client/actions/VoiceStateUpdate.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 const VoiceState = require('../../structures/VoiceState');
diff --git a/src/client/actions/WebhooksUpdate.js b/src/client/actions/WebhooksUpdate.js
index 08ec838f..69e28aec 100644
--- a/src/client/actions/WebhooksUpdate.js
+++ b/src/client/actions/WebhooksUpdate.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Action = require('./Action');
 const { Events } = require('../../util/Constants');
 
diff --git a/src/client/voice/ClientVoiceManager.js b/src/client/voice/ClientVoiceManager.js
index d55a809f..a9081efd 100644
--- a/src/client/voice/ClientVoiceManager.js
+++ b/src/client/voice/ClientVoiceManager.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Collection = require('../../util/Collection');
 const { VoiceStatus } = require('../../util/Constants');
 const VoiceConnection = require('./VoiceConnection');
diff --git a/src/client/voice/VoiceBroadcast.js b/src/client/voice/VoiceBroadcast.js
index 1bc4e282..602f5920 100644
--- a/src/client/voice/VoiceBroadcast.js
+++ b/src/client/voice/VoiceBroadcast.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const EventEmitter = require('events');
 const BroadcastAudioPlayer = require('./player/BroadcastAudioPlayer');
 const DispatcherSet = require('./util/DispatcherSet');
diff --git a/src/client/voice/VoiceConnection.js b/src/client/voice/VoiceConnection.js
index 6a4d4cda..078781b5 100644
--- a/src/client/voice/VoiceConnection.js
+++ b/src/client/voice/VoiceConnection.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const VoiceWebSocket = require('./networking/VoiceWebSocket');
 const VoiceUDP = require('./networking/VoiceUDPClient');
 const Util = require('../../util/Util');
diff --git a/src/client/voice/dispatcher/BroadcastDispatcher.js b/src/client/voice/dispatcher/BroadcastDispatcher.js
index 90cff6a4..e5c7650c 100644
--- a/src/client/voice/dispatcher/BroadcastDispatcher.js
+++ b/src/client/voice/dispatcher/BroadcastDispatcher.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const StreamDispatcher = require('./StreamDispatcher');
 
 /**
diff --git a/src/client/voice/dispatcher/StreamDispatcher.js b/src/client/voice/dispatcher/StreamDispatcher.js
index 7bb0ef1b..93c6df81 100644
--- a/src/client/voice/dispatcher/StreamDispatcher.js
+++ b/src/client/voice/dispatcher/StreamDispatcher.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const VolumeInterface = require('../util/VolumeInterface');
 const { Writable } = require('stream');
 
diff --git a/src/client/voice/networking/VoiceUDPClient.js b/src/client/voice/networking/VoiceUDPClient.js
index fe34cab3..c1dd9e3d 100644
--- a/src/client/voice/networking/VoiceUDPClient.js
+++ b/src/client/voice/networking/VoiceUDPClient.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const udp = require('dgram');
 const { VoiceOPCodes } = require('../../../util/Constants');
 const EventEmitter = require('events');
diff --git a/src/client/voice/networking/VoiceWebSocket.js b/src/client/voice/networking/VoiceWebSocket.js
index bd03ea54..d556145b 100644
--- a/src/client/voice/networking/VoiceWebSocket.js
+++ b/src/client/voice/networking/VoiceWebSocket.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { OPCodes, VoiceOPCodes } = require('../../../util/Constants');
 const EventEmitter = require('events');
 const { Error } = require('../../../errors');
diff --git a/src/client/voice/player/AudioPlayer.js b/src/client/voice/player/AudioPlayer.js
index e3381f5c..3ce94d81 100644
--- a/src/client/voice/player/AudioPlayer.js
+++ b/src/client/voice/player/AudioPlayer.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const BasePlayer = require('./BasePlayer');
 
 /**
diff --git a/src/client/voice/player/BasePlayer.js b/src/client/voice/player/BasePlayer.js
index e19984df..c9c6cf0d 100644
--- a/src/client/voice/player/BasePlayer.js
+++ b/src/client/voice/player/BasePlayer.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const EventEmitter = require('events').EventEmitter;
 const { Readable: ReadableStream } = require('stream');
 const prism = require('prism-media');
diff --git a/src/client/voice/player/BroadcastAudioPlayer.js b/src/client/voice/player/BroadcastAudioPlayer.js
index 052c9ea0..c1cab9f4 100644
--- a/src/client/voice/player/BroadcastAudioPlayer.js
+++ b/src/client/voice/player/BroadcastAudioPlayer.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const BroadcastDispatcher = require('../dispatcher/BroadcastDispatcher');
 const BasePlayer = require('./BasePlayer');
 
diff --git a/src/client/voice/receiver/PacketHandler.js b/src/client/voice/receiver/PacketHandler.js
index 1ea702c1..7189f112 100644
--- a/src/client/voice/receiver/PacketHandler.js
+++ b/src/client/voice/receiver/PacketHandler.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const secretbox = require('../util/Secretbox');
 const EventEmitter = require('events');
 
diff --git a/src/client/voice/receiver/Receiver.js b/src/client/voice/receiver/Receiver.js
index 1174f70b..605d9927 100644
--- a/src/client/voice/receiver/Receiver.js
+++ b/src/client/voice/receiver/Receiver.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const EventEmitter = require('events');
 const prism = require('prism-media');
 const PacketHandler = require('./PacketHandler');
diff --git a/src/client/voice/util/DispatcherSet.js b/src/client/voice/util/DispatcherSet.js
index a1ab7e94..38a7c8b6 100644
--- a/src/client/voice/util/DispatcherSet.js
+++ b/src/client/voice/util/DispatcherSet.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { Events } = require('../../../util/Constants');
 
 /**
diff --git a/src/client/voice/util/PlayInterface.js b/src/client/voice/util/PlayInterface.js
index 58d31141..ac66eb29 100644
--- a/src/client/voice/util/PlayInterface.js
+++ b/src/client/voice/util/PlayInterface.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { Readable } = require('stream');
 const prism = require('prism-media');
 const { Error } = require('../../../errors');
diff --git a/src/client/voice/util/Secretbox.js b/src/client/voice/util/Secretbox.js
index fe1eebe8..1b30eeb6 100644
--- a/src/client/voice/util/Secretbox.js
+++ b/src/client/voice/util/Secretbox.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const libs = {
   sodium: sodium => ({
     open: sodium.api.crypto_secretbox_open_easy,
diff --git a/src/client/voice/util/Silence.js b/src/client/voice/util/Silence.js
index b9643da1..2068d763 100644
--- a/src/client/voice/util/Silence.js
+++ b/src/client/voice/util/Silence.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { Readable } = require('stream');
 
 const SILENCE_FRAME = Buffer.from([0xF8, 0xFF, 0xFE]);
diff --git a/src/client/voice/util/VolumeInterface.js b/src/client/voice/util/VolumeInterface.js
index 95645f91..a631e6ca 100644
--- a/src/client/voice/util/VolumeInterface.js
+++ b/src/client/voice/util/VolumeInterface.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const EventEmitter = require('events');
 
 /**
diff --git a/src/client/websocket/WebSocketManager.js b/src/client/websocket/WebSocketManager.js
index 891da3f4..fd749968 100644
--- a/src/client/websocket/WebSocketManager.js
+++ b/src/client/websocket/WebSocketManager.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Collection = require('../../util/Collection');
 const WebSocketShard = require('./WebSocketShard');
 const { Events, Status, WSEvents } = require('../../util/Constants');
diff --git a/src/client/websocket/WebSocketShard.js b/src/client/websocket/WebSocketShard.js
index 7aec37e2..6237b051 100644
--- a/src/client/websocket/WebSocketShard.js
+++ b/src/client/websocket/WebSocketShard.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const EventEmitter = require('events');
 const WebSocket = require('../../WebSocket');
 const { Status, Events, OPCodes, WSEvents, WSCodes } = require('../../util/Constants');
diff --git a/src/client/websocket/handlers/CHANNEL_CREATE.js b/src/client/websocket/handlers/CHANNEL_CREATE.js
index 3074254f..d6d560d8 100644
--- a/src/client/websocket/handlers/CHANNEL_CREATE.js
+++ b/src/client/websocket/handlers/CHANNEL_CREATE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.ChannelCreate.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/CHANNEL_DELETE.js b/src/client/websocket/handlers/CHANNEL_DELETE.js
index 158ccb35..cb9f3d8c 100644
--- a/src/client/websocket/handlers/CHANNEL_DELETE.js
+++ b/src/client/websocket/handlers/CHANNEL_DELETE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.ChannelDelete.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/CHANNEL_PINS_UPDATE.js b/src/client/websocket/handlers/CHANNEL_PINS_UPDATE.js
index 1272dbbb..dfc854e3 100644
--- a/src/client/websocket/handlers/CHANNEL_PINS_UPDATE.js
+++ b/src/client/websocket/handlers/CHANNEL_PINS_UPDATE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { Events } = require('../../../util/Constants');
 
 module.exports = (client, { d: data }) => {
diff --git a/src/client/websocket/handlers/CHANNEL_UPDATE.js b/src/client/websocket/handlers/CHANNEL_UPDATE.js
index 46d9037a..b437ebbd 100644
--- a/src/client/websocket/handlers/CHANNEL_UPDATE.js
+++ b/src/client/websocket/handlers/CHANNEL_UPDATE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { Events } = require('../../../util/Constants');
 
 module.exports = (client, packet) => {
diff --git a/src/client/websocket/handlers/GUILD_BAN_ADD.js b/src/client/websocket/handlers/GUILD_BAN_ADD.js
index 00772c8c..4fa89edc 100644
--- a/src/client/websocket/handlers/GUILD_BAN_ADD.js
+++ b/src/client/websocket/handlers/GUILD_BAN_ADD.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { Events } = require('../../../util/Constants');
 
 module.exports = (client, { d: data }) => {
diff --git a/src/client/websocket/handlers/GUILD_BAN_REMOVE.js b/src/client/websocket/handlers/GUILD_BAN_REMOVE.js
index 08483a83..8389e46e 100644
--- a/src/client/websocket/handlers/GUILD_BAN_REMOVE.js
+++ b/src/client/websocket/handlers/GUILD_BAN_REMOVE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.GuildBanRemove.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/GUILD_CREATE.js b/src/client/websocket/handlers/GUILD_CREATE.js
index 05250ed6..9f13c658 100644
--- a/src/client/websocket/handlers/GUILD_CREATE.js
+++ b/src/client/websocket/handlers/GUILD_CREATE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { Events, Status } = require('../../../util/Constants');
 
 module.exports = async (client, { d: data }, shard) => {
diff --git a/src/client/websocket/handlers/GUILD_DELETE.js b/src/client/websocket/handlers/GUILD_DELETE.js
index 19d1b3b0..27a32562 100644
--- a/src/client/websocket/handlers/GUILD_DELETE.js
+++ b/src/client/websocket/handlers/GUILD_DELETE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.GuildDelete.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/GUILD_EMOJIS_UPDATE.js b/src/client/websocket/handlers/GUILD_EMOJIS_UPDATE.js
index 5fa5a9d5..e23b6713 100644
--- a/src/client/websocket/handlers/GUILD_EMOJIS_UPDATE.js
+++ b/src/client/websocket/handlers/GUILD_EMOJIS_UPDATE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.GuildEmojisUpdate.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/GUILD_INTEGRATIONS_UPDATE.js b/src/client/websocket/handlers/GUILD_INTEGRATIONS_UPDATE.js
index 6c1a0cfd..e90a72c2 100644
--- a/src/client/websocket/handlers/GUILD_INTEGRATIONS_UPDATE.js
+++ b/src/client/websocket/handlers/GUILD_INTEGRATIONS_UPDATE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.GuildIntegrationsUpdate.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/GUILD_MEMBERS_CHUNK.js b/src/client/websocket/handlers/GUILD_MEMBERS_CHUNK.js
index 7178264d..0738eaa6 100644
--- a/src/client/websocket/handlers/GUILD_MEMBERS_CHUNK.js
+++ b/src/client/websocket/handlers/GUILD_MEMBERS_CHUNK.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { Events } = require('../../../util/Constants');
 const Collection = require('../../../util/Collection');
 
diff --git a/src/client/websocket/handlers/GUILD_MEMBER_ADD.js b/src/client/websocket/handlers/GUILD_MEMBER_ADD.js
index 367058a5..796b6c37 100644
--- a/src/client/websocket/handlers/GUILD_MEMBER_ADD.js
+++ b/src/client/websocket/handlers/GUILD_MEMBER_ADD.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { Events, Status } = require('../../../util/Constants');
 
 module.exports = (client, { d: data }, shard) => {
diff --git a/src/client/websocket/handlers/GUILD_MEMBER_REMOVE.js b/src/client/websocket/handlers/GUILD_MEMBER_REMOVE.js
index b00da0e6..72432af1 100644
--- a/src/client/websocket/handlers/GUILD_MEMBER_REMOVE.js
+++ b/src/client/websocket/handlers/GUILD_MEMBER_REMOVE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet, shard) => {
   client.actions.GuildMemberRemove.handle(packet.d, shard);
 };
diff --git a/src/client/websocket/handlers/GUILD_MEMBER_UPDATE.js b/src/client/websocket/handlers/GUILD_MEMBER_UPDATE.js
index be4f573a..9341329a 100644
--- a/src/client/websocket/handlers/GUILD_MEMBER_UPDATE.js
+++ b/src/client/websocket/handlers/GUILD_MEMBER_UPDATE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { Status, Events } = require('../../../util/Constants');
 
 module.exports = (client, { d: data }, shard) => {
diff --git a/src/client/websocket/handlers/GUILD_ROLE_CREATE.js b/src/client/websocket/handlers/GUILD_ROLE_CREATE.js
index b6ea8038..da9e7bc4 100644
--- a/src/client/websocket/handlers/GUILD_ROLE_CREATE.js
+++ b/src/client/websocket/handlers/GUILD_ROLE_CREATE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.GuildRoleCreate.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/GUILD_ROLE_DELETE.js b/src/client/websocket/handlers/GUILD_ROLE_DELETE.js
index d1093cb2..cdc63531 100644
--- a/src/client/websocket/handlers/GUILD_ROLE_DELETE.js
+++ b/src/client/websocket/handlers/GUILD_ROLE_DELETE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.GuildRoleDelete.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/GUILD_ROLE_UPDATE.js b/src/client/websocket/handlers/GUILD_ROLE_UPDATE.js
index c1f526c5..3a9b62e8 100644
--- a/src/client/websocket/handlers/GUILD_ROLE_UPDATE.js
+++ b/src/client/websocket/handlers/GUILD_ROLE_UPDATE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.GuildRoleUpdate.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/GUILD_SYNC.js b/src/client/websocket/handlers/GUILD_SYNC.js
index f27da424..b7e7d1b2 100644
--- a/src/client/websocket/handlers/GUILD_SYNC.js
+++ b/src/client/websocket/handlers/GUILD_SYNC.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.GuildSync.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/GUILD_UPDATE.js b/src/client/websocket/handlers/GUILD_UPDATE.js
index 0f3e24f7..fd0012ad 100644
--- a/src/client/websocket/handlers/GUILD_UPDATE.js
+++ b/src/client/websocket/handlers/GUILD_UPDATE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.GuildUpdate.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/MESSAGE_CREATE.js b/src/client/websocket/handlers/MESSAGE_CREATE.js
index bc9303fd..c9b79a8f 100644
--- a/src/client/websocket/handlers/MESSAGE_CREATE.js
+++ b/src/client/websocket/handlers/MESSAGE_CREATE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.MessageCreate.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/MESSAGE_DELETE.js b/src/client/websocket/handlers/MESSAGE_DELETE.js
index 09062196..85ae2bc7 100644
--- a/src/client/websocket/handlers/MESSAGE_DELETE.js
+++ b/src/client/websocket/handlers/MESSAGE_DELETE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.MessageDelete.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/MESSAGE_DELETE_BULK.js b/src/client/websocket/handlers/MESSAGE_DELETE_BULK.js
index a927b3b1..fbcf80fd 100644
--- a/src/client/websocket/handlers/MESSAGE_DELETE_BULK.js
+++ b/src/client/websocket/handlers/MESSAGE_DELETE_BULK.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.MessageDeleteBulk.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/MESSAGE_REACTION_ADD.js b/src/client/websocket/handlers/MESSAGE_REACTION_ADD.js
index e2ac2c07..6d0bbb05 100644
--- a/src/client/websocket/handlers/MESSAGE_REACTION_ADD.js
+++ b/src/client/websocket/handlers/MESSAGE_REACTION_ADD.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { Events } = require('../../../util/Constants');
 
 module.exports = (client, packet) => {
diff --git a/src/client/websocket/handlers/MESSAGE_REACTION_REMOVE.js b/src/client/websocket/handlers/MESSAGE_REACTION_REMOVE.js
index 8b9f22a1..2980e695 100644
--- a/src/client/websocket/handlers/MESSAGE_REACTION_REMOVE.js
+++ b/src/client/websocket/handlers/MESSAGE_REACTION_REMOVE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.MessageReactionRemove.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/MESSAGE_REACTION_REMOVE_ALL.js b/src/client/websocket/handlers/MESSAGE_REACTION_REMOVE_ALL.js
index 2323cfe0..ead80f75 100644
--- a/src/client/websocket/handlers/MESSAGE_REACTION_REMOVE_ALL.js
+++ b/src/client/websocket/handlers/MESSAGE_REACTION_REMOVE_ALL.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.MessageReactionRemoveAll.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/MESSAGE_UPDATE.js b/src/client/websocket/handlers/MESSAGE_UPDATE.js
index 9be750c7..7428e90c 100644
--- a/src/client/websocket/handlers/MESSAGE_UPDATE.js
+++ b/src/client/websocket/handlers/MESSAGE_UPDATE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { Events } = require('../../../util/Constants');
 
 module.exports = (client, packet) => {
diff --git a/src/client/websocket/handlers/PRESENCE_UPDATE.js b/src/client/websocket/handlers/PRESENCE_UPDATE.js
index 89b9f0e2..bde36297 100644
--- a/src/client/websocket/handlers/PRESENCE_UPDATE.js
+++ b/src/client/websocket/handlers/PRESENCE_UPDATE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.PresenceUpdate.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/READY.js b/src/client/websocket/handlers/READY.js
index f22968d3..74b1e1b9 100644
--- a/src/client/websocket/handlers/READY.js
+++ b/src/client/websocket/handlers/READY.js
@@ -1,3 +1,5 @@
+'use strict';
+
 let ClientUser;
 
 module.exports = (client, { d: data }, shard) => {
diff --git a/src/client/websocket/handlers/RESUMED.js b/src/client/websocket/handlers/RESUMED.js
index 6cc355e9..bd00ec88 100644
--- a/src/client/websocket/handlers/RESUMED.js
+++ b/src/client/websocket/handlers/RESUMED.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { Events } = require('../../../util/Constants');
 
 module.exports = (client, packet, shard) => {
diff --git a/src/client/websocket/handlers/TYPING_START.js b/src/client/websocket/handlers/TYPING_START.js
index ac01d30d..9df76dc7 100644
--- a/src/client/websocket/handlers/TYPING_START.js
+++ b/src/client/websocket/handlers/TYPING_START.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { Events } = require('../../../util/Constants');
 
 module.exports = (client, { d: data }) => {
diff --git a/src/client/websocket/handlers/USER_UPDATE.js b/src/client/websocket/handlers/USER_UPDATE.js
index 3c5b859c..a02bf588 100644
--- a/src/client/websocket/handlers/USER_UPDATE.js
+++ b/src/client/websocket/handlers/USER_UPDATE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.UserUpdate.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/VOICE_SERVER_UPDATE.js b/src/client/websocket/handlers/VOICE_SERVER_UPDATE.js
index c8ac3883..2663d99a 100644
--- a/src/client/websocket/handlers/VOICE_SERVER_UPDATE.js
+++ b/src/client/websocket/handlers/VOICE_SERVER_UPDATE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.emit('self.voiceServer', packet.d);
 };
diff --git a/src/client/websocket/handlers/VOICE_STATE_UPDATE.js b/src/client/websocket/handlers/VOICE_STATE_UPDATE.js
index a9527ada..dbff6ea2 100644
--- a/src/client/websocket/handlers/VOICE_STATE_UPDATE.js
+++ b/src/client/websocket/handlers/VOICE_STATE_UPDATE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.VoiceStateUpdate.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/WEBHOOKS_UPDATE.js b/src/client/websocket/handlers/WEBHOOKS_UPDATE.js
index b1afb91c..46cacee0 100644
--- a/src/client/websocket/handlers/WEBHOOKS_UPDATE.js
+++ b/src/client/websocket/handlers/WEBHOOKS_UPDATE.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = (client, packet) => {
   client.actions.WebhooksUpdate.handle(packet.d);
 };
diff --git a/src/client/websocket/handlers/index.js b/src/client/websocket/handlers/index.js
index 77bcf8fd..b253cefe 100644
--- a/src/client/websocket/handlers/index.js
+++ b/src/client/websocket/handlers/index.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { WSEvents } = require('../../../util/Constants');
 
 const handlers = {};
diff --git a/src/errors/DJSError.js b/src/errors/DJSError.js
index 1d5aea12..157ca660 100644
--- a/src/errors/DJSError.js
+++ b/src/errors/DJSError.js
@@ -1,3 +1,5 @@
+'use strict';
+
 // Heavily inspired by node's `internal/errors` module
 
 const kCode = Symbol('code');
diff --git a/src/errors/Messages.js b/src/errors/Messages.js
index 5f237ac5..792c2b8b 100644
--- a/src/errors/Messages.js
+++ b/src/errors/Messages.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { register } = require('./DJSError');
 
 const Messages = {
diff --git a/src/errors/index.js b/src/errors/index.js
index 39b7582d..c94ddc78 100644
--- a/src/errors/index.js
+++ b/src/errors/index.js
@@ -1,2 +1,4 @@
+'use strict';
+
 module.exports = require('./DJSError');
 module.exports.Messages = require('./Messages');
diff --git a/src/index.js b/src/index.js
index a124108f..1747f68c 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Util = require('./util/Util');
 
 module.exports = {
diff --git a/src/rest/APIRequest.js b/src/rest/APIRequest.js
index ec8375dd..7b0a73e4 100644
--- a/src/rest/APIRequest.js
+++ b/src/rest/APIRequest.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const querystring = require('querystring');
 const FormData = require('form-data');
 const https = require('https');
diff --git a/src/rest/APIRouter.js b/src/rest/APIRouter.js
index 06ebeb3f..715b1c7c 100644
--- a/src/rest/APIRouter.js
+++ b/src/rest/APIRouter.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const noop = () => {}; // eslint-disable-line no-empty-function
 const methods = ['get', 'post', 'delete', 'patch', 'put'];
 const reflectors = [
diff --git a/src/rest/DiscordAPIError.js b/src/rest/DiscordAPIError.js
index c90ee4f5..559194f2 100644
--- a/src/rest/DiscordAPIError.js
+++ b/src/rest/DiscordAPIError.js
@@ -1,3 +1,5 @@
+'use strict';
+
 /**
  * Represents an error from the Discord API.
  * @extends Error
diff --git a/src/rest/HTTPError.js b/src/rest/HTTPError.js
index 32b3e6bd..2911467f 100644
--- a/src/rest/HTTPError.js
+++ b/src/rest/HTTPError.js
@@ -1,3 +1,5 @@
+'use strict';
+
 /**
  * Represents a HTTP error from a request.
  * @extends Error
diff --git a/src/rest/RESTManager.js b/src/rest/RESTManager.js
index 53a8047f..306fa246 100644
--- a/src/rest/RESTManager.js
+++ b/src/rest/RESTManager.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const RequestHandler = require('./RequestHandler');
 const APIRequest = require('./APIRequest');
 const routeBuilder = require('./APIRouter');
diff --git a/src/rest/RequestHandler.js b/src/rest/RequestHandler.js
index 3f66fd43..44fca4fb 100644
--- a/src/rest/RequestHandler.js
+++ b/src/rest/RequestHandler.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const DiscordAPIError = require('./DiscordAPIError');
 const HTTPError = require('./HTTPError');
 const Util = require('../util/Util');
diff --git a/src/sharding/Shard.js b/src/sharding/Shard.js
index 3b25c1d0..adc5caeb 100644
--- a/src/sharding/Shard.js
+++ b/src/sharding/Shard.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const EventEmitter = require('events');
 const path = require('path');
 const Util = require('../util/Util');
diff --git a/src/sharding/ShardClientUtil.js b/src/sharding/ShardClientUtil.js
index 201568ca..026c97ef 100644
--- a/src/sharding/ShardClientUtil.js
+++ b/src/sharding/ShardClientUtil.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Util = require('../util/Util');
 const { Events } = require('../util/Constants');
 
diff --git a/src/sharding/ShardingManager.js b/src/sharding/ShardingManager.js
index b7196229..aca3ebed 100644
--- a/src/sharding/ShardingManager.js
+++ b/src/sharding/ShardingManager.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const path = require('path');
 const fs = require('fs');
 const EventEmitter = require('events');
diff --git a/src/stores/ChannelStore.js b/src/stores/ChannelStore.js
index 6e2e4081..8d491c83 100644
--- a/src/stores/ChannelStore.js
+++ b/src/stores/ChannelStore.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const DataStore = require('./DataStore');
 const Channel = require('../structures/Channel');
 const { Events } = require('../util/Constants');
diff --git a/src/stores/DataStore.js b/src/stores/DataStore.js
index 3708893c..fc841899 100644
--- a/src/stores/DataStore.js
+++ b/src/stores/DataStore.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Collection = require('../util/Collection');
 let Structures;
 
diff --git a/src/stores/GuildChannelStore.js b/src/stores/GuildChannelStore.js
index e67bcc1c..e538889d 100644
--- a/src/stores/GuildChannelStore.js
+++ b/src/stores/GuildChannelStore.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Channel = require('../structures/Channel');
 const { ChannelTypes } = require('../util/Constants');
 const DataStore = require('./DataStore');
diff --git a/src/stores/GuildEmojiRoleStore.js b/src/stores/GuildEmojiRoleStore.js
index e2fe5ecd..8c097f56 100644
--- a/src/stores/GuildEmojiRoleStore.js
+++ b/src/stores/GuildEmojiRoleStore.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Collection = require('../util/Collection');
 const Util = require('../util/Util');
 const { TypeError } = require('../errors');
diff --git a/src/stores/GuildEmojiStore.js b/src/stores/GuildEmojiStore.js
index 925f79ab..b992a68c 100644
--- a/src/stores/GuildEmojiStore.js
+++ b/src/stores/GuildEmojiStore.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Collection = require('../util/Collection');
 const DataStore = require('./DataStore');
 const GuildEmoji = require('../structures/GuildEmoji');
diff --git a/src/stores/GuildMemberRoleStore.js b/src/stores/GuildMemberRoleStore.js
index 205de123..8789df21 100644
--- a/src/stores/GuildMemberRoleStore.js
+++ b/src/stores/GuildMemberRoleStore.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Collection = require('../util/Collection');
 const Util = require('../util/Util');
 const { TypeError } = require('../errors');
diff --git a/src/stores/GuildMemberStore.js b/src/stores/GuildMemberStore.js
index 6f95aec9..039fb4c7 100644
--- a/src/stores/GuildMemberStore.js
+++ b/src/stores/GuildMemberStore.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const DataStore = require('./DataStore');
 const GuildMember = require('../structures/GuildMember');
 const { Events, OPCodes } = require('../util/Constants');
diff --git a/src/stores/GuildStore.js b/src/stores/GuildStore.js
index 0cf9a115..90e4358d 100644
--- a/src/stores/GuildStore.js
+++ b/src/stores/GuildStore.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const DataStore = require('./DataStore');
 const DataResolver = require('../util/DataResolver');
 const { Events } = require('../util/Constants');
diff --git a/src/stores/MessageStore.js b/src/stores/MessageStore.js
index 2d704979..1a8a7083 100644
--- a/src/stores/MessageStore.js
+++ b/src/stores/MessageStore.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const DataStore = require('./DataStore');
 const Collection = require('../util/Collection');
 const Message = require('../structures/Message');
diff --git a/src/stores/PresenceStore.js b/src/stores/PresenceStore.js
index 15fc9f12..061d3f1e 100644
--- a/src/stores/PresenceStore.js
+++ b/src/stores/PresenceStore.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const DataStore = require('./DataStore');
 const { Presence } = require('../structures/Presence');
 
diff --git a/src/stores/ReactionStore.js b/src/stores/ReactionStore.js
index 38c467b7..b3910ba4 100644
--- a/src/stores/ReactionStore.js
+++ b/src/stores/ReactionStore.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const DataStore = require('./DataStore');
 const MessageReaction = require('../structures/MessageReaction');
 
diff --git a/src/stores/ReactionUserStore.js b/src/stores/ReactionUserStore.js
index 1b027579..976b7991 100644
--- a/src/stores/ReactionUserStore.js
+++ b/src/stores/ReactionUserStore.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Collection = require('../util/Collection');
 const DataStore = require('./DataStore');
 const { Error } = require('../errors');
diff --git a/src/stores/RoleStore.js b/src/stores/RoleStore.js
index 3c3a5b35..14956c30 100644
--- a/src/stores/RoleStore.js
+++ b/src/stores/RoleStore.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const DataStore = require('./DataStore');
 const Role = require('../structures/Role');
 const { resolveColor } = require('../util/Util');
diff --git a/src/stores/UserStore.js b/src/stores/UserStore.js
index d700877c..8fd2d9d5 100644
--- a/src/stores/UserStore.js
+++ b/src/stores/UserStore.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const DataStore = require('./DataStore');
 const User = require('../structures/User');
 const GuildMember = require('../structures/GuildMember');
diff --git a/src/stores/VoiceStateStore.js b/src/stores/VoiceStateStore.js
index 2de49249..ece3c2bb 100644
--- a/src/stores/VoiceStateStore.js
+++ b/src/stores/VoiceStateStore.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const DataStore = require('./DataStore');
 const VoiceState = require('../structures/VoiceState');
 
diff --git a/src/structures/APIMessage.js b/src/structures/APIMessage.js
index 8b714fcd..deca5d26 100644
--- a/src/structures/APIMessage.js
+++ b/src/structures/APIMessage.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const DataResolver = require('../util/DataResolver');
 const MessageEmbed = require('./MessageEmbed');
 const MessageAttachment = require('./MessageAttachment');
diff --git a/src/structures/Base.js b/src/structures/Base.js
index 37633757..4850a39d 100644
--- a/src/structures/Base.js
+++ b/src/structures/Base.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Util = require('../util/Util');
 
 /**
diff --git a/src/structures/CategoryChannel.js b/src/structures/CategoryChannel.js
index 5766a4a7..60be408c 100644
--- a/src/structures/CategoryChannel.js
+++ b/src/structures/CategoryChannel.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const GuildChannel = require('./GuildChannel');
 
 /**
diff --git a/src/structures/Channel.js b/src/structures/Channel.js
index 8466d19a..92914118 100644
--- a/src/structures/Channel.js
+++ b/src/structures/Channel.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Snowflake = require('../util/Snowflake');
 const Base = require('./Base');
 const { ChannelTypes } = require('../util/Constants');
diff --git a/src/structures/ClientApplication.js b/src/structures/ClientApplication.js
index 7ea36020..d2bcd17a 100644
--- a/src/structures/ClientApplication.js
+++ b/src/structures/ClientApplication.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Snowflake = require('../util/Snowflake');
 const { ClientApplicationAssetTypes, Endpoints } = require('../util/Constants');
 const Base = require('./Base');
diff --git a/src/structures/ClientPresence.js b/src/structures/ClientPresence.js
index 68dda64c..a92dfb30 100644
--- a/src/structures/ClientPresence.js
+++ b/src/structures/ClientPresence.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { Presence } = require('./Presence');
 const Collection = require('../util/Collection');
 const { ActivityTypes, OPCodes } = require('../util/Constants');
diff --git a/src/structures/ClientUser.js b/src/structures/ClientUser.js
index 1b8d90d9..79d7ad0e 100644
--- a/src/structures/ClientUser.js
+++ b/src/structures/ClientUser.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Structures = require('../util/Structures');
 const DataResolver = require('../util/DataResolver');
 
diff --git a/src/structures/DMChannel.js b/src/structures/DMChannel.js
index 1f45f490..5549618a 100644
--- a/src/structures/DMChannel.js
+++ b/src/structures/DMChannel.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Channel = require('./Channel');
 const TextBasedChannel = require('./interfaces/TextBasedChannel');
 const MessageStore = require('../stores/MessageStore');
diff --git a/src/structures/Emoji.js b/src/structures/Emoji.js
index ed844f18..803fc500 100644
--- a/src/structures/Emoji.js
+++ b/src/structures/Emoji.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Snowflake = require('../util/Snowflake');
 const Base = require('./Base');
 
diff --git a/src/structures/GroupDMChannel.js b/src/structures/GroupDMChannel.js
index b2fe7200..6f9aca39 100644
--- a/src/structures/GroupDMChannel.js
+++ b/src/structures/GroupDMChannel.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Channel = require('./Channel');
 const TextBasedChannel = require('./interfaces/TextBasedChannel');
 const Collection = require('../util/Collection');
diff --git a/src/structures/Guild.js b/src/structures/Guild.js
index a194ea15..aef0b311 100644
--- a/src/structures/Guild.js
+++ b/src/structures/Guild.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Invite = require('./Invite');
 const Integration = require('./Integration');
 const GuildAuditLogs = require('./GuildAuditLogs');
diff --git a/src/structures/GuildAuditLogs.js b/src/structures/GuildAuditLogs.js
index a5212d5b..f78078a7 100644
--- a/src/structures/GuildAuditLogs.js
+++ b/src/structures/GuildAuditLogs.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Collection = require('../util/Collection');
 const Snowflake = require('../util/Snowflake');
 const Webhook = require('./Webhook');
diff --git a/src/structures/GuildChannel.js b/src/structures/GuildChannel.js
index daf20a52..dc0a4e41 100644
--- a/src/structures/GuildChannel.js
+++ b/src/structures/GuildChannel.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Channel = require('./Channel');
 const Role = require('./Role');
 const Invite = require('./Invite');
diff --git a/src/structures/GuildEmoji.js b/src/structures/GuildEmoji.js
index 93e8d275..24fd7c02 100644
--- a/src/structures/GuildEmoji.js
+++ b/src/structures/GuildEmoji.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const GuildEmojiRoleStore = require('../stores/GuildEmojiRoleStore');
 const Permissions = require('../util/Permissions');
 const { Error } = require('../errors');
diff --git a/src/structures/GuildMember.js b/src/structures/GuildMember.js
index a2e82d79..d91071c9 100644
--- a/src/structures/GuildMember.js
+++ b/src/structures/GuildMember.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const TextBasedChannel = require('./interfaces/TextBasedChannel');
 const Role = require('./Role');
 const Permissions = require('../util/Permissions');
diff --git a/src/structures/Integration.js b/src/structures/Integration.js
index 2782008b..5ff760dc 100644
--- a/src/structures/Integration.js
+++ b/src/structures/Integration.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Base = require('./Base');
 
 /**
diff --git a/src/structures/Invite.js b/src/structures/Invite.js
index b142d696..fec3f2d7 100644
--- a/src/structures/Invite.js
+++ b/src/structures/Invite.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { Endpoints } = require('../util/Constants');
 const Base = require('./Base');
 
diff --git a/src/structures/Message.js b/src/structures/Message.js
index 88a1707a..1947705e 100644
--- a/src/structures/Message.js
+++ b/src/structures/Message.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Mentions = require('./MessageMentions');
 const MessageAttachment = require('./MessageAttachment');
 const Embed = require('./MessageEmbed');
diff --git a/src/structures/MessageAttachment.js b/src/structures/MessageAttachment.js
index cce6e487..a4c05303 100644
--- a/src/structures/MessageAttachment.js
+++ b/src/structures/MessageAttachment.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Util = require('../util/Util');
 
 /**
diff --git a/src/structures/MessageCollector.js b/src/structures/MessageCollector.js
index 3d9fcf72..59120b9d 100644
--- a/src/structures/MessageCollector.js
+++ b/src/structures/MessageCollector.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Collector = require('./interfaces/Collector');
 const { Events } = require('../util/Constants');
 
diff --git a/src/structures/MessageEmbed.js b/src/structures/MessageEmbed.js
index 49ddf30a..213a27a1 100644
--- a/src/structures/MessageEmbed.js
+++ b/src/structures/MessageEmbed.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Util = require('../util/Util');
 const { RangeError } = require('../errors');
 
diff --git a/src/structures/MessageMentions.js b/src/structures/MessageMentions.js
index bd99397d..b4414a3b 100644
--- a/src/structures/MessageMentions.js
+++ b/src/structures/MessageMentions.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Collection = require('../util/Collection');
 const Util = require('../util/Util');
 const GuildMember = require('./GuildMember');
diff --git a/src/structures/MessageReaction.js b/src/structures/MessageReaction.js
index faf3bfbf..69138fda 100644
--- a/src/structures/MessageReaction.js
+++ b/src/structures/MessageReaction.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const GuildEmoji = require('./GuildEmoji');
 const Util = require('../util/Util');
 const ReactionEmoji = require('./ReactionEmoji');
diff --git a/src/structures/PermissionOverwrites.js b/src/structures/PermissionOverwrites.js
index b2851786..cf11eaa9 100644
--- a/src/structures/PermissionOverwrites.js
+++ b/src/structures/PermissionOverwrites.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Role = require('./Role');
 const Permissions = require('../util/Permissions');
 const Util = require('../util/Util');
diff --git a/src/structures/Presence.js b/src/structures/Presence.js
index 33998134..122b461d 100644
--- a/src/structures/Presence.js
+++ b/src/structures/Presence.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Util = require('../util/Util');
 const ActivityFlags = require('../util/ActivityFlags');
 const { ActivityTypes } = require('../util/Constants');
diff --git a/src/structures/ReactionCollector.js b/src/structures/ReactionCollector.js
index 5c4532e2..b4826100 100644
--- a/src/structures/ReactionCollector.js
+++ b/src/structures/ReactionCollector.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Collector = require('./interfaces/Collector');
 const Collection = require('../util/Collection');
 const { Events } = require('../util/Constants');
diff --git a/src/structures/ReactionEmoji.js b/src/structures/ReactionEmoji.js
index c6ea8d68..2661fa91 100644
--- a/src/structures/ReactionEmoji.js
+++ b/src/structures/ReactionEmoji.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Util = require('../util/Util');
 const Emoji = require('./Emoji');
 
diff --git a/src/structures/Role.js b/src/structures/Role.js
index 18f68f2f..cbae5696 100644
--- a/src/structures/Role.js
+++ b/src/structures/Role.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Snowflake = require('../util/Snowflake');
 const Permissions = require('../util/Permissions');
 const Util = require('../util/Util');
diff --git a/src/structures/TextChannel.js b/src/structures/TextChannel.js
index 6e053e5d..47c8e19c 100644
--- a/src/structures/TextChannel.js
+++ b/src/structures/TextChannel.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const GuildChannel = require('./GuildChannel');
 const Webhook = require('./Webhook');
 const TextBasedChannel = require('./interfaces/TextBasedChannel');
diff --git a/src/structures/User.js b/src/structures/User.js
index 67366323..22ea5c81 100644
--- a/src/structures/User.js
+++ b/src/structures/User.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const TextBasedChannel = require('./interfaces/TextBasedChannel');
 const { Presence } = require('./Presence');
 const Snowflake = require('../util/Snowflake');
diff --git a/src/structures/VoiceChannel.js b/src/structures/VoiceChannel.js
index aee01b6f..cf9b1ee9 100644
--- a/src/structures/VoiceChannel.js
+++ b/src/structures/VoiceChannel.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const GuildChannel = require('./GuildChannel');
 const { browser } = require('../util/Constants');
 const Permissions = require('../util/Permissions');
diff --git a/src/structures/VoiceRegion.js b/src/structures/VoiceRegion.js
index b4db2177..9626195d 100644
--- a/src/structures/VoiceRegion.js
+++ b/src/structures/VoiceRegion.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Util = require('../util/Util');
 
 /**
diff --git a/src/structures/VoiceState.js b/src/structures/VoiceState.js
index 88e0ed19..82f9eec7 100644
--- a/src/structures/VoiceState.js
+++ b/src/structures/VoiceState.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Base = require('./Base');
 
 /**
diff --git a/src/structures/Webhook.js b/src/structures/Webhook.js
index c12cc67f..7b851c77 100644
--- a/src/structures/Webhook.js
+++ b/src/structures/Webhook.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const DataResolver = require('../util/DataResolver');
 const Channel = require('./Channel');
 const APIMessage = require('./APIMessage');
diff --git a/src/structures/interfaces/Collector.js b/src/structures/interfaces/Collector.js
index c490ebb3..1dbd6142 100644
--- a/src/structures/interfaces/Collector.js
+++ b/src/structures/interfaces/Collector.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Collection = require('../../util/Collection');
 const Util = require('../../util/Util');
 const EventEmitter = require('events');
diff --git a/src/structures/interfaces/TextBasedChannel.js b/src/structures/interfaces/TextBasedChannel.js
index f9c668de..075bc675 100644
--- a/src/structures/interfaces/TextBasedChannel.js
+++ b/src/structures/interfaces/TextBasedChannel.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const MessageCollector = require('../MessageCollector');
 const Snowflake = require('../../util/Snowflake');
 const Collection = require('../../util/Collection');
diff --git a/src/util/ActivityFlags.js b/src/util/ActivityFlags.js
index 49fd7a67..f6f5aac9 100644
--- a/src/util/ActivityFlags.js
+++ b/src/util/ActivityFlags.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const BitField = require('./BitField');
 
 /**
diff --git a/src/util/BitField.js b/src/util/BitField.js
index fa506a2e..96b07b82 100644
--- a/src/util/BitField.js
+++ b/src/util/BitField.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { RangeError } = require('../errors');
 
 /**
diff --git a/src/util/Collection.js b/src/util/Collection.js
index 7f0570d6..3d01ffef 100644
--- a/src/util/Collection.js
+++ b/src/util/Collection.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Util = require('./Util');
 
 /**
diff --git a/src/util/Constants.js b/src/util/Constants.js
index 01ff57d6..aac3f5b3 100644
--- a/src/util/Constants.js
+++ b/src/util/Constants.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Package = exports.Package = require('../../package.json');
 const { Error, RangeError } = require('../errors');
 const browser = exports.browser = typeof window !== 'undefined';
diff --git a/src/util/DataResolver.js b/src/util/DataResolver.js
index 5fcfd0d4..1b905727 100644
--- a/src/util/DataResolver.js
+++ b/src/util/DataResolver.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const path = require('path');
 const fs = require('fs');
 const fetch = require('node-fetch');
diff --git a/src/util/Permissions.js b/src/util/Permissions.js
index 295346b1..9f01df39 100644
--- a/src/util/Permissions.js
+++ b/src/util/Permissions.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const BitField = require('./BitField');
 
 /**
diff --git a/src/util/Snowflake.js b/src/util/Snowflake.js
index 00f22d06..06612c30 100644
--- a/src/util/Snowflake.js
+++ b/src/util/Snowflake.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Util = require('../util/Util');
 
 // Discord epoch (2015-01-01T00:00:00.000Z)
diff --git a/src/util/Speaking.js b/src/util/Speaking.js
index e0e557ea..c706d995 100644
--- a/src/util/Speaking.js
+++ b/src/util/Speaking.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const BitField = require('./BitField');
 
 /**
diff --git a/src/util/Structures.js b/src/util/Structures.js
index 8b1edd8b..5bdf5c86 100644
--- a/src/util/Structures.js
+++ b/src/util/Structures.js
@@ -1,3 +1,5 @@
+'use strict';
+
 /**
  * Allows for the extension of built-in Discord.js structures that are instantiated by {@link DataStore DataStores}.
  */
diff --git a/src/util/Util.js b/src/util/Util.js
index 562b81a4..1d7b7aee 100644
--- a/src/util/Util.js
+++ b/src/util/Util.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const { Colors, DefaultOptions, Endpoints } = require('./Constants');
 const fetch = require('node-fetch');
 const { Error: DiscordError, RangeError, TypeError } = require('../errors');
diff --git a/webpack.config.js b/webpack.config.js
index c7416852..c95745f1 100644
--- a/webpack.config.js
+++ b/webpack.config.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const path = require('path');
 const webpack = require('webpack');
 const TerserJSPlugin = require('terser-webpack-plugin');