WordPress Plugin i18n Workflow

Model note: Fully mechanical — POT generation, PO/MO compilation, and script registration are tool invocations. haiku handles all steps; no cross-file reasoning needed.

Full translation pipeline for WordPress plugins: POT generation, PO/MO compilation, JavaScript translations, translate.wordpress.org GlotPress, and language pack distribution. Covers the coding conventions and the tooling workflow.

When to use

• "Generate a POT file for my plugin", "update translation strings".
• "Set up JavaScript translations", "translate strings in React/block editor".
• "Submit to translate.wordpress.org", "set up language packs".
• "Why aren't my translations loading?", "debug missing .mo file".
• "Add translator comments", "handle plurals and context strings".

Not for: PHPCS i18n sniff violations — use wp-coding-standards. Checking i18n completeness in an audit — use wp-plugin-audit Dimension B.

Method

1. PHP i18n conventions

All translatable strings must use the plugin's text domain consistently. The text domain must match the Text Domain: header and the load_plugin_textdomain() call.

// Basic translation
__( 'Settings', 'my-plugin' )
_e( 'Save Changes', 'my-plugin' )        // echo version

// With HTML context (escape + translate combined)
esc_html__( 'Error message', 'my-plugin' )
esc_attr__( 'Tooltip text', 'my-plugin' )

// Plurals
_n( '%d item', '%d items', $count, 'my-plugin' )
sprintf( _n( '%d item', '%d items', $count, 'my-plugin' ), $count )

// Context strings (disambiguation for translators)
_x( 'Post', 'noun: a blog post', 'my-plugin' )
_ex( 'Draft', 'verb: save as draft', 'my-plugin' )

// Plural with context
_nx( '%d reply', '%d replies', $count, 'comment count', 'my-plugin' )

Translator comments — required for strings with placeholders:

/* translators: %s: plugin version number */
sprintf( __( 'Version %s', 'my-plugin' ), MY_PLUGIN_VERSION )

/* translators: 1: post title, 2: author name */
sprintf( __( '"%1$s" by %2$s', 'my-plugin' ), $title, $author )

Comment must be on the line immediately before the function call and start with translators:.

2. Load text domain

add_action( 'init', function() {
    load_plugin_textdomain(
        'my-plugin',
        false,
        dirname( plugin_basename( __FILE__ ) ) . '/languages/'
    );
} );

For WP.org plugins, language packs are auto-loaded from translate.wordpress.org — load_plugin_textdomain() only needed for bundled .mo files or local development.

3. Generate POT file

# WP-CLI (preferred)
wp i18n make-pot . languages/my-plugin.pot \
  --domain=my-plugin \
  --exclude=vendor,node_modules,tests,build \
  --headers='{"Project-Id-Version":"My Plugin 1.0.0","Report-Msgid-Bugs-To":"https://github.com/my-org/my-plugin/issues"}'

# Update existing POT (merges new strings, marks removed as obsolete)
wp i18n make-pot . languages/my-plugin.pot --domain=my-plugin

Commit languages/my-plugin.pot to git. Translators use this as the source.

4. Compile PO → MO

.po files are human-editable; .mo are compiled binary files loaded by PHP.

# Single file
wp i18n make-mo languages/my-plugin-fr_FR.po

# All PO files in the directory
wp i18n make-mo languages/

# Using msgfmt (gettext tools)
msgfmt languages/my-plugin-fr_FR.po -o languages/my-plugin-fr_FR.mo

File naming convention: {text-domain}-{locale}.po / .mo Examples: my-plugin-fr_FR.mo, my-plugin-de_DE.mo, my-plugin-pt_BR.mo

5. JavaScript translations

Block editor / React components — use @wordpress/i18n:

import { __, _n, _x, sprintf } from '@wordpress/i18n';

const label = __( 'Save settings', 'my-plugin' );
const count = sprintf( _n( '%d item', '%d items', total, 'my-plugin' ), total );
const ctx   = _x( 'Draft', 'button label', 'my-plugin' );

Generate JSON translation files:

# From PO file — produces my-plugin-fr_FR-{hash}.json
wp i18n make-json languages/my-plugin-fr_FR.po --no-purge

Register JS translations in PHP:

function my_plugin_set_script_translations() {
    wp_set_script_translations(
        'my-plugin-editor',   // script handle (must be enqueued)
        'my-plugin',          // text domain
        plugin_dir_path( __FILE__ ) . 'languages'
    );
}
add_action( 'init', 'my_plugin_set_script_translations' );

For blocks registered via block.json, WP auto-calls wp_set_script_translations if textdomain is set in block.json:

{
    "textdomain": "my-plugin",
    "editorScript": "file:./index.js"
}

6. translate.wordpress.org (GlotPress)

WP.org plugins get a GlotPress project automatically once approved. Language packs are built weekly and distributed via the WP update system.

Setup steps:

1. Plugin approved on WP.org → GlotPress project auto-created at translate.wordpress.org/projects/wp-plugins/your-slug/
2. Ensure languages/ dir exists in SVN trunk with the .pot file
3. GlotPress imports strings from trunk automatically (or trigger via SVN commit)
4. Community translators contribute at translate.wordpress.org
5. At 95% translation completion, a language pack is created and distributed to users

WP.org translation validator: https://i18n.svn.wordpress.org/

Correct POT headers for GlotPress:

Project-Id-Version: My Plugin 1.0.0
Report-Msgid-Bugs-To: https://wordpress.org/support/plugin/my-plugin
Last-Translator: FULL NAME <EMAIL@ADDRESS>
Language-Team: LANGUAGE <[email protected]>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

7. Debugging missing translations

Checklist:

# 1. Verify text domain matches header and load_plugin_textdomain()
grep -r "Text Domain:" *.php
grep -r "load_plugin_textdomain" includes/

# 2. Verify .mo file exists and locale matches WP locale
wp option get WPLANG   # should match e.g. fr_FR
ls languages/          # should have my-plugin-fr_FR.mo

# 3. Verify .mo can be loaded
wp eval "echo load_plugin_textdomain('my-plugin', false, 'path/to/languages/');"

# 4. Verify string is in POT
grep -A2 "your string" languages/my-plugin.pot

# 5. For JS translations — check JSON files exist
ls languages/*.json

# 6. Check wp_set_script_translations fires after script is enqueued
# (Must call AFTER wp_enqueue_script, usually on 'init' or 'enqueue_scripts')

Common failure modes:

8. Automation — sync POT on release

Add to GitHub Actions or release workflow:

- name: Generate POT
  run: wp i18n make-pot . languages/my-plugin.pot --domain=my-plugin --exclude=vendor,node_modules,build
- name: Compile MO files
  run: wp i18n make-mo languages/
- name: Generate JS JSON
  run: wp i18n make-json languages/ --no-purge

Notes

• Never concatenate translatable strings: __( 'Hello' ) . ' ' . __( 'World' ) — translators can't reorder. Use sprintf( __( 'Hello %s', 'my-plugin' ), $name ).
• Never use variables as the first argument: __( $dynamic_string, 'my-plugin' ) — POT extractors can't find these strings.
• RTL languages (Arabic, Hebrew, Farsi): WordPress detects RTL from the locale and loads rtl.css automatically. Mirror your style.css in style-rtl.css for layout flips.
• wp i18n commands require WP-CLI 2.2+. In CI, install via curl -O https://raw.githubusercontent.com/wp-cli/builds/gh-pages/phar/wp-cli.phar.

References

• references/js-i18n-patterns.md — JavaScript i18n patterns using @wordpress/i18n: __(), _n(), sprintf() usage, Gutenberg block translation, and dynamic string handling
• references/pot-commands.md — WP-CLI i18n command reference: make-pot, make-mo, make-json, update-po with all options and CI-ready invocations
• references/translation-debugging.md — Translation debugging guide: common failure modes, locale loading order, .mo vs .json file issues, and QM debug tools