Build Your First Plugin

Create a small Illegalcord plugin inside the local source tree.

This guide creates PrefixEveryMessage, a small plugin that adds a configurable prefix to outgoing messages. It uses the declarative onBeforeMessageSend field, so PluginManager handles registration and cleanup.

Create the folder

Create:

src/userplugins/prefixEveryMessage/index.ts

Add the plugin

/*
 * Vencord, a Discord client mod
 * Copyright (c) 2026 Vendicated and contributors
 * SPDX-License-Identifier: GPL-3.0-or-later
 */

import { definePluginSettings } from "@api/Settings";
import type { MessageObject } from "@api/MessageEvents";
import { EquicordDevs } from "@utils/constants";
import definePlugin, { OptionType } from "@utils/types";

const settings = definePluginSettings({
    enabled: {
        type: OptionType.BOOLEAN,
        description: "Add the prefix to outgoing messages.",
        default: true
    },
    prefix: {
        type: OptionType.STRING,
        description: "Text to add before each outgoing message.",
        default: "[Illegalcord] "
    }
});

export default definePlugin({
    name: "PrefixEveryMessage",
    description: "Adds a configurable prefix to messages you send.",
    authors: [EquicordDevs.irritably],
    settings,

    onBeforeMessageSend(_channelId: string, message: MessageObject) {
        const { enabled, prefix } = settings.store;
        if (!enabled || !message.content.trim()) return;

        message.content = prefix + message.content;
    }
});

Replace EquicordDevs.irritably with your own author entry before submitting the plugin.

Build and test

Run:

pnpm build
pnpm inject

Restart Discord, open Illegalcord Settings > Plugins, search for PrefixEveryMessage, and enable it.

Configure it

Open the plugin cog wheel and edit:

Setting	Default
Add the prefix to outgoing messages.	true
Text to add before each outgoing message.	[Illegalcord]

Send a test message in a private test channel.

Clean up

This plugin uses a declarative field, so no manual stop() cleanup is needed. If you later add timers, event listeners, manual API registrations, or Flux subscriptions outside declarative fields, clean them up in stop().

Do not keep this plugin enabled in normal chats unless you intentionally want every sent message modified.