etherpad-lite/doc/plugins.md

Plugins

Etherpad allows you to extend its functionality with plugins. A plugin registers hooks (functions) for certain events (thus certain features) in Etherpad to execute its own functionality based on these events.

Publicly available plugins can be found in the npm registry (see https://npmjs.org). Etherpad's naming convention for plugins is to prefix your plugins with ep_. So, e.g. it's ep_flubberworms. Thus you can install plugins from npm, using pnpm run plugins install ep_flubberworms in Etherpad's root directory.

Also see wiki article for more info.

You can also browse to http://yourEtherpadInstan.ce/admin/plugins, which will list all installed plugins and those available on npm. It even provides functionality to search through all available plugins.

Folder structure

Ideally a plugin has the following folder structure:

ep_<plugin>/
 ├ .github/
 │  └ workflows/
 │     └ npmpublish.yml  ◄─ GitHub workflow to auto-publish on push
 ├ static/
 │  ├ css/               ◄─ static .css files
 │  ├ images/            ◄─ static image files
 │  ├ js/
 │  │  └ index.js        ◄─ static client-side code
 │  └ tests/
 │     ├ backend/
 │     │  └ specs/       ◄─ backend (server) tests
 │     └ frontend/
 │        └ specs/       ◄─ frontend (client) tests
 ├ templates/            ◄─ EJS templates (.html, .js, .css, etc.)
 ├ locales/
 │  ├ en.json            ◄─ English (US) strings
 │  └ qqq.json           ◄─ optional hints for translators
 ├ .github/workflows/   ◄─ CI workflows (backend / frontend tests, npm publish)
 ├ LICENSE
 ├ README.md
 ├ ep.json               ◄─ Etherpad plugin definition
 ├ index.js              ◄─ server-side code
 ├ package.json
 └ package-lock.json

If your plugin includes client-side hooks, put them in static/js/. If you're adding in CSS or image files, you should put those files in static/css/ and static/image/, respectively, and templates go into templates/. Translations go into locales/. Tests go in static/tests/backend/specs/ and static/tests/frontend/specs/.

A Standard directory structure like this makes it easier to navigate through your code. That said, do note, that this is not actually required to make your plugin run. If you want to make use of our i18n system, you need to put your translations into locales/, though, in order to have them integrated. (See "Localization" for more info on how to localize your plugin.)

Plugin definition

Your plugin definition goes into ep.json. In this file you register your hook functions, indicate the parts of your plugin and the order of execution. (A documentation of all available events to hook into can be found in chapter hooks.)

{
  "parts": [
    {
      "name": "nameThisPartHoweverYouWant",
      "hooks": {
        "authenticate": "ep_<plugin>/<file>:functionName1",
        "expressCreateServer": "ep_<plugin>/<file>:functionName2"
      },
      "client_hooks": {
        "acePopulateDOMLine": "ep_<plugin>/<file>:functionName3"
      }
    }
  ]
}

A hook function registration maps a hook name to a hook function specification. The hook function specification looks like ep_example/file.js:functionName. It consists of two parts separated by a colon: a module name to require() and the name of a function exported by the named module. See module.exports for how to export a function.

For the module name you can omit the .js suffix, and if the file is index.js you can use just the directory name. You can also omit the module name entirely, in which case it defaults to the plugin name (e.g., ep_example).

You can also omit the function name. If you do, Etherpad will look for an exported function whose name matches the name of the hook (e.g., authenticate).

If either the module name or the function name is omitted (or both), the colon may also be omitted unless the provided module name contains a colon. (So if the module name is C:\foo.js then the hook function specification with the function name omitted would be "C:\\foo.js:".)

Examples: Suppose the plugin name is ep_example. All of the following are equivalent, and will cause the authorize hook to call the exports.authorize function in index.js from the ep_example plugin:

• "authorize": "ep_example/index.js:authorize"
• "authorize": "ep_example/index.js:"
• "authorize": "ep_example/index.js"
• "authorize": "ep_example/index:authorize"
• "authorize": "ep_example/index:"
• "authorize": "ep_example/index"
• "authorize": "ep_example:authorize"
• "authorize": "ep_example:"
• "authorize": "ep_example"
• "authorize": ":authorize"
• "authorize": ":"
• "authorize": ""

Client hooks and server hooks

There are server hooks, which will be executed on the server (e.g. expressCreateServer), and there are client hooks, which are executed on the client (e.g. acePopulateDomLine). Be sure to not make assumptions about the environment your code is running in, e.g. don't try to access process, if you know your code will be run on the client, and likewise, don't try to access window on the server...

Styling

When you install a client-side plugin (e.g. one that implements at least one client-side hook), the plugin name is added to the class attribute of the div #editorcontainerbox in the main window. This gives you the opportunity of tuning the appearance of the main UI in your plugin.

For example, this is the markup with no plugins installed:

<div id="editorcontainerbox" class="">

and this is the contents after installing someplugin:

<div id="editorcontainerbox" class="ep_someplugin">

This feature was introduced in Etherpad 1.8.

Parts

As your plugins become more and more complex, you will find yourself in the need to manage dependencies between plugins. E.g. you want the hooks of a certain plugin to be executed before (or after) yours. You can also manage these dependencies in your plugin definition file ep.json:

{
  "parts": [
    {
      "name": "onepart",
      "pre": [],
      "post": ["ep_onemoreplugin/partone"]
      "hooks": {
        "storeBar": "ep_monospace/plugin:storeBar",
        "getFoo": "ep_monospace/plugin:getFoo",
      }
    },
    {
      "name": "otherpart",
      "pre": ["ep_my_example/somepart", "ep_otherplugin/main"],
      "post": [],
      "hooks": {
        "someEvent": "ep_my_example/otherpart:someEvent",
        "another": "ep_my_example/otherpart:another"
      }
    }
  ]
}

Usually a plugin will add only one functionality at a time, so it will probably only use one part definition to register its hooks. However, sometimes you have to put different (unrelated) functionalities into one plugin. For this you will want use parts, so other plugins can depend on them.

pre/post

The "pre" and "post" definitions, affect the order in which parts of a plugin are executed. This ensures that plugins and their hooks are executed in the correct order.

"pre" lists parts that must be executed before the defining part. "post" lists parts that must be executed after the defining part.

You can, on a basic level, think of this as double-ended dependency listing. If you have a dependency on another plugin, you can make sure it loads before yours by putting it in "pre". If you are setting up things that might need to be used by a plugin later, you can ensure proper order by putting it in "post".

Note that it would be far more sane to use "pre" in almost any case, but if you want to change config variables for another plugin, or maybe modify its environment, "post" could definitely be useful.

Also, note that dependencies should also be listed in your package.json, so they can be npm install'd automagically when your plugin gets installed.

Package definition

Your plugin must also contain a package definition file, called package.json, in the project root - this file contains various metadata relevant to your plugin, such as the name and version number, author, project hompage, contributors, a short description, etc. If you publish your plugin on npm, these metadata are used for package search etc., but it's necessary for Etherpad plugins, even if you don't publish your plugin.

{
  "name": "ep_PLUGINNAME",
  "version": "0.0.1",
  "description": "DESCRIPTION",
  "author": "USERNAME (REAL NAME) <MAIL@EXAMPLE.COM>",
  "contributors": [],
  "dependencies": {"MODULE": "0.3.20"},
  "engines": {"node": ">=12.17.0"}
}

Templates

If your plugin adds or modifies the front end HTML (e.g. adding buttons or changing their functions), you should put the necessary HTML code for such operations in templates/, in files of type ".ejs", since Etherpad uses EJS for HTML templating. See the following link for more information about EJS: https://github.com/visionmedia/ejs.

Plugin-namespaced pad-wide options

Plugins can ride the existing padoptions COLLABROOM rail to store pad-wide settings — broadcast to every connected client, persisted with the pad, and honored by enforceSettings — instead of inventing their own message type and storage. The model matches how enablePadWideSettings works for native toggles like sticky chat or line numbers.

Capability detection

let padOptionsPluginPassthrough = false;
try {
  // The require throws on Etherpad versions that predate this capability;
  // plugins should degrade gracefully (typically falling back to a per-user
  // cookie toggle) when the flag is missing.
  padOptionsPluginPassthrough =
      require('ep_etherpad-lite/node/utils/PluginCapabilities')
          .padOptionsPluginPassthrough === true;
} catch (_e) { /* older core */ }

The flag means the core has the passthrough patch available. Whether it is actually enabled at runtime is a separate per-instance setting — see below.

Runtime flag

The passthrough is gated by settings.enablePluginPadOptions, default false. Operators must opt in via settings.json:

{
  "enablePluginPadOptions": true
}

When enabled, the server reflects the value to every client via clientVars.enablePluginPadOptions so plugins can detect both capable (static) and active (per-pad request) at the same point.

Key namespace

Plugins must use keys matching /^ep_[a-z0-9_]+$/. The recommended pattern is ep_<plugin_name> (e.g. ep_table_of_contents); compose multiple pad-wide settings under one key as a plain object:

pad.changePadOption('ep_my_plugin', {enabled: true, depth: 3});

The server passes through any matching key on the existing padoptions message, persists it with the pad, and broadcasts it to every connected client. pad.padOptions.ep_my_plugin reflects the latest value on every client.

Validation

Server-side Pad.normalizePadSettings() enforces three rules on every plugin-namespaced key:

• Values must round-trip through JSON.stringify (no functions, symbols, BigInt, or circular references).
• Each key's serialized payload must fit within 64 KB.
• The combined size of all ep_* values per pad must fit within 256 KB.

Values that fail any of these rules are dropped with a console.warn; the rest of the settings round-trip cleanly. The caps prevent a misbehaving plugin from bloating the persisted pad payload or the COLLABROOM broadcast.

Writing and running front-end tests for your plugin

Etherpad allows you to easily create front-end tests for plugins.

1. Create a new folder: %your_plugin%/static/tests/frontend/specs
2. Put your spec file in there. (Example spec files are visible in %etherpad_root_folder%/frontend/tests/specs.)
3. Visit http://yourserver.com/frontend/tests and your front-end tests will run.