Omeka S includes support for presenting interfaces to users in different languages. The source strings for Omeka and its modules are written in English, and we rely on volunteers to translate those strings.


Omeka S stores translated strings in the gettext format. There are three basic types of file:

  • a .pot file is a translation template: it contains only the English-language source strings.
  • .po files are where translated strings are stored. They're the same as the .pot file, except the translations for each string are filled in. Each language has its own .po file.
  • .mo files are compiled versions of .po files. The .mo file is what Omeka S actually uses to read and use the translated strings for a particular language.

All three of these types of file are found in the languages directory (application/languages for the core). Generally, translators will deal with the first two types through Transifex (see next section).


Omeka S uses the Transifex platform to allow a simpler way for people to contribute translations. The core and modules written by the Omeka team are handled through the same project on Transifex. Through the Transifex site, you can join existing translation teams, request new languages, and make changes or contributions to the translations.

Making strings translatable

When writing code in Omeka S, strings that will be presented to the user need some special handling so that they can be translated.

Direct translation: within a view

Instead of writing strings directly in the markup, use the translate() helper.

As a simple real example, see this line from the installer view:

<h1><?php echo $this->translate('Install Omeka S'); ?></h1>

Using translate() will handle actually replacing the English source string with the translated equivalent, and also serve as a marker that a string is translatable for when we build the translation template that makes strings available to the translators.

Indirect translation: within forms and other classes

Code that uses the Zend\Form classes will automatically translate strings that get presented to the user like labels, legends, and descriptions.

Several other areas where user-facing strings are defined are also automatically translated, such as labels for site blocks and media ingesters, labels for navigation entries defined in config files, and error messages.

In these situations, all that's necessary is to comment the line to be translated with // @translate at the end of the line. The translation itself will happen with or without the comment, but the comment is needed so our automated template processing will pick up the string to be translated and make it available to the translation teams.

The // @translate comment applies only to the immediately-previous string. If a single line contains multiple strings that need to be marked as translatable, or has one translatable string that appears in between untranslatable ones, it may be necessary to split the original line into multiple lines.

Here's an example of using the // @translate comment in the site navigation section of a module's module.config.php file:

return [
    'navigation' => [
        'site' => [
                'label' => 'Collecting', // @translate
                'route' => 'admin/site/slug/collecting',
                'action' => 'index',
                'useRouteMatch' => true,
                'pages' => [
                    // .....

And here's one from a form class that extends Zend\Form\Form:

public function init()
        'name' => 'o:email',
        'type' => 'Email',
        'options' => [
            'label' => 'Email', // @translate
        'attributes' => [
            'id' => 'email',
            'required' => true,

Handling strings with dynamic parts

The previous examples are focused on simple, static strings, but often it's necessary to have strings with parts that change, like data that comes from users, or counts of search results. Simply passing the existing string as-is to the translation system won't work correctly: every change in the data will be treated as a "new" string that won't get translated.

In those situations, the dynamic part of the string must be replaced by a "placeholder," leading to a translatable part that stays the same, which the dynamic parts are then inserted into. To do this, Omeka S uses the PHP function sprintf.

The basic placeholder for sprintf is %s. It's simplest to show an example of how this gets used to make a dynamic string translatable. The following untranslated code:

There are <?php echo $this->escapeHtml($results); ?> results.

becomes this when translated:

<?php echo sprintf($this->translate('There are %s results.'), $this->escapeHtml($results)); ?>

Note that the call to translate() is inside the call to sprintf.

There's a slightly more complex style of placeholder that's used when one string contains multiple dynamic parts. Some languages may need to reorder these parts in a different way than the original English string, which means there needs to be something that differentiates the first placeholder from the second, and so on. These placeholders look like this: %1$s, %2$s, and so on.

There's a slightly different method used when dealing with these "dynamic" strings outside of views (in places like class files, for example). Instead of using sprintf directly, there's a class Omeka\Stdlib\Message that is used to pass the static and dynamic parts of the string around together.

use Omeka\Stdlib\Message;

// ...
    function exampleAction()
        $message = new Message('There are %s results.', $results); // @translate

The resulting Message object can be passed directly to translate() in a view. This pattern is used often for error messages that can originate from deep within backend code but still need to be presented to the user, and therefore translated.

Updating translation files

Omeka S includes several Gulp tasks for working with the translation files. The tasks all start with i18n (an abbreviation for "internationalization"). In addition to having Gulp set up, these tasks require the gettext package, which provides commands such as msgfmt and xgettext that are used to work with the translation files.

gulp i18n:template updates the core's .pot translation template. When strings are added or changed, this task updates the template so it can be pushed to translators to in turn update their translations. The Omeka team runs this command and then pushes the result to Transifex.

gulp i18n:compile is run after updating .po files to compile them into .mo files. Just updating the .po translation file isn't enough to get Omeka S to pick up the changes; the .mo file is what's actually used. The Omeka team runs this command after pulling down updates from Transifex.

For further commands used for working with modules rather than the core, see the documentation on internationalization in modules.