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guideUsing package generator

The ckeditor5-package-generator is a tool for developers, and it creates a working package with the development environment that allows writing new custom plugins for CKEditor 5.

# Quick start

To create a new package without installing the tool, execute the following command:

npx ckeditor5-package-generator <packageName> [--verbose] [--use-npm]

The <packageName> argument is required and must follow these rules:

  • The provided name must match the schema: @scope/ckeditor5-*, where @scope is an owner of the package.
  • The package name must start with the ckeditor5- prefix.
  • Allowed characters are numbers (0-9), lowercase letters (a-z) and symbols: - . _.

As a result of executing the command, a new directory with a package will be created. The directory’s name will be equal to the specified package name without the @scope part, and it will contain an example plugin and the development environment.

Available modifiers for the command are:

  • --verbose – (alias: -v) whether to prints additional logs about the current executed task.
  • --use-npm – whether to use npm instead of yarn when installing dependencies in a newly created package.

After successfully creating the new package, enter it by executing the following command:

# Assuming that your package was created with `ckeditor5-foo` as its name.
cd ckeditor5-foo

Then run the test environment for the plugin by executing:

npm run start

There, the plugin can be seen within the example editor.

# Structure of the project

An overview of the project’s directory structure:

├─ lang
│  └─ contexts.json        # Entries used for creating translations.
├─ sample
│  ├─ dll.html             # The editor initialized using the DLL builds.
│  ├─ index.html           # The sample file.
│  └─ ckeditor.js          # The editor initialization script.
├─ src
│  ├─ index.js             # The modules exported by the package when using the DLL builds.
│  ├─ myplugin.js          # Very basic plugin that utilizes the CKEditor 5 framework.
│  └─ **/*.js              # All JavaScript source files should be saved here.
├─ tests
│  ├─ index.js             # Tests for the plugin.
│  ├─ myplugin.js
│  └─ **/*.js              # All tests should be saved here.
├─ theme
│  ├─ icons
│  │  ├─ ckeditor.svg      # The CKEditor 5 icon displayed in the toolbar.
│  │  └─ **/*.svg          # All icon files should be saved here.
│  └─ **/*.css             # All CSS files should be saved here.
├─ .editorconfig           # See link below for details.
├─ .eslintrc.js            # ESLint configuration file.
├─ .gitattributes          # See link below for details.
├─ .gitignore              # See link below for details.
├─ .stylelintrc            # Stylelint configuration file.
├─ ckeditor5-metadata.json # See link below for details.
├─              # All created packages fall under the MIT license.
├─ package.json            # See link below for details.
└─               # Description of your project and usage instructions.

Guides for developing some files:

# Npm scripts

Npm scripts are a convenient way to provide commands in a project. They are defined in the package.json file and shared with other people contributing to the project. It ensures that developers use the same command with the same options (flags).

All the scripts can be executed by running npm run <script>. Pre and post commands with matching names will be run for those as well.

The following scripts are available in the package.

# start

Starts a HTTP server with the live-reload mechanism that allows previewing and testing plugins available in the package.

When the server has been started, the default browser will open the developer sample. This can be disabled by passing the --no-open option to that command.

You can also define the language that will translate the created editor by specifying the --language [LANG] option. It defaults to 'en'.


# Starts the server and open the browser.
npm run start

# Disable auto-opening the browser.
npm run start -- --no-open

# Create the editor with the interface in German.
npm run start -- --language=de

# test

Allows executing unit tests for the package, specified in the tests/ directory. The command accepts the following modifiers:

  • --coverage – to create the code coverage report,
  • --watch – to observe the source files (the command does not end after executing tests),
  • --source-map – to generate source maps of sources,
  • --verbose – to print additional webpack logs.


# Execute tests.
npm run test

# Generate code coverage report after each change in the sources.
npm run test -- --coverage --test

# lint

Runs ESLint, which analyzes the code (all *.js files) to quickly find problems.


# Execute ESLint.
npm run lint

# stylelint

Similar to the lint task, stylelint analyzes the CSS code (*.css files in the theme/ directory) in the package.


# Execute stylelint.
npm run stylelint

# dll:build

Creates a DLL-compatible package build which can be loaded into an editor using DLL builds.


# Build the DLL file that is ready to publish.
npm run dll:build

# Build the DLL file and listen to changes in its sources.
npm run dll:build -- --watch

# dll:serve

Creates a simple HTTP server (without the live-reload mechanism) that allows verifying whether the DLL build of the package is compatible with the CKEditor 5 DLL builds.


# Starts the HTTP server and opens the browser.
npm run dll:serve

# translations:collect

Collects translation messages (arguments of the t() function) and context files, then validates whether the provided values do not interfere with the values specified in the @ckeditor/ckeditor5-core package.

The task may end with an error if one of the following conditions is met:

  • Found the Unused context error – entries specified in the lang/contexts.json file are not used in source files. They should be removed.
  • Found the Context is duplicated for the id error – some of the entries are duplicated. Consider removing them from the lang/contexts.json file, or rewrite them.
  • Found the Context for the message id is missing error – entries specified in source files are not described in the lang/contexts.json file. They should be added.


npm run translations:collect

# translations:download

Download translations from the Transifex server. Depending on users’ activity in the project, it creates translations files used for building the editor.

The task requires passing the URL to Transifex API. Usually, it matches the following format:[PROJECT_SLUG].

To avoid passing the --transifex option every time when calls the command, you can store it in package.json, next to the ckeditor5-package-tools translations:upload command.


npm run translations:download -- --transifex [API URL]

# translations:upload

Uploads translation messages onto the Transifex server. It allows for the creation of translations into other languages by users using the Transifex platform.

The task requires passing the URL to the Transifex API. Usually, it matches the following format:[PROJECT_SLUG].

To avoid passing the --transifex option every time when you call the command, you can store it in package.json, next to the ckeditor5-package-tools translations:upload command.


npm run translations:upload -- --transifex [API URL]

# prepare and prepublishOnly

Npm supports some special life cycle scripts that allow performing operations on your package before it is published. In the context of the generated package, they just create a DLL-compatible package build.

# How to change ESLint configuration?

To change ESLint config, edit the .eslintrc.js file. It is also a good idea to check out the ESLint docs.

To make CKEditor 5 plugins compatible with each other, we needed to introduce limitations when importing files from packages. To learn more, visit the DLL guide and see detailed explanation about the limitation.

# Translations

Packages created by this tool, just like the entirety of the CKEditor 5 ecosystem include full support for localization. If you wish to include translations for your package, visit the docs page and learn more.

The package contains several tools for handling translations in the created package. We recommend the following flow when dealing with translations:

  1. Call npm run translations:download – download the latest version of translations.
    • If there are changes in the lang/translations/* files, commit them as they represent new or updated translation files.
  2. Call npm run translations:collect – verify whether contexts are up-to-date.
  3. Call npm run translations:upload – upload new translations.
  4. Call npm run translations:download – if new contexts were uploaded, it updates the en.po file in the package. Do not forget to commit the change.

# Reporting issues

If you found a problem with CKEditor 5 or the package generator, please, report an issue: