XLIFF Format

The XML Localization Interchange File Format (or XLIFF) is an OASIS-blessed standard format for translations.

In a nutshell, an XLIFF document contains one or more <file> elements. Each file element usually corresponds to a source (file or database table) and contains the source of the localizable data. Once translated, the corresponding localized data is added for one, and only one, locale.

Localizable data is stored in <trans-unit> elements. <trans-unit> contains a <source> element to store the source text and a (non-mandatory) <target> element to store the translated text.

The default language is always English, even if you have changed your TYPO3 backend to another language. It is mandatory to set source-language="en".

Note

Having several <file> elements in the same XLIFF document is not supported by the TYPO3 Core.

Basics

Here is a sample XLIFF file:

EXT:my_ext/Resources/Private/Language/Modules/<file-name>.xlf
<?xml version="1.0" encoding="UTF-8"?>
<xliff version="1.2" xmlns="urn:oasis:names:tc:xliff:document:1.2">
    <file source-language="en" datatype="plaintext" original="EXT:my_ext/Resources/Private/Language/Modules/<file-name>.xlf" date="2020-10-18T18:20:51Z" product-name="my_ext">
        <header/>
        <body>
            <trans-unit id="headerComment" resname="headerComment">
                <source>The default Header Comment.</source>
            </trans-unit>
            <trans-unit id="generator" resname="generator">
                <source>The "Generator" Meta Tag.</source>
            </trans-unit>
        </body>
    </file>
</xliff>

The following attributes should be populated properly in order to get the best support in external translation tools:

original (in <file> tag)

This property contains the path to the xlf file.

resname (in <trans-unit> tag)

Its content is shown to translators. It should be a copy of the id property.

The translated file is very similar. If the original file was named locallang.xlf, the translated file for German (code "de") will be named de.locallang.xlf.

Note

The original file must always be in English, so it is not allowed to create a file with the prefix "en", for example en.locallang.xlf.

In the file itself, a target-language attribute is added to the <file> tag to indicate the translation language ("de" in our example). Then, for each <source> tag there is a sibling <target> tag that contains the translated string.

This is how the translation of our sample file might look like:

EXT:my_ext/Resources/Private/Language/Modules/<file-name>.xlf
<?xml version="1.0" encoding="UTF-8"?>
<xliff version="1.2" xmlns="urn:oasis:names:tc:xliff:document:1.2">
    <file source-language="en" target-language="de" datatype="plaintext" original="EXT:my_ext/Resources/Private/Language/Modules/<file-name>.xlf" date="2020-10-18T18:20:51Z" product-name="my_ext">
        <header/>
        <body>
            <trans-unit id="headerComment" resname="headerComment" approved="yes">
                <source>The default Header Comment.</source>
                <target>Der Standard-Header-Kommentar.</target>
            </trans-unit>
            <trans-unit id="generator" resname="generator" approved="yes">
                <source>The "Generator" Meta Tag.</source>
                <target>Der "Generator"-Meta-Tag.</target>
            </trans-unit>
        </body>
    </file>
</xliff>

Only one language can be stored per file, and each translation into another language is placed in an additional file.

Note

The optional approved attribute in a <trans-unit> tag indicates whether the translation has been approved by a reviewer. Crowdin supports this attribute. Currently, only approved translations are exported and available via the TYPO3 translation server.

File locations and naming

In the TYPO3 Core, XLIFF files are located in the various system extensions as needed and are expected to be located in Resources/Private/Language.

In Extbase, the main file (locallang.xlf) is loaded automatically and is available in the controller and Fluid views without any further work. Other files must be explicitly referenced with the syntax LLL:EXT:extkey/Resources/Private/Language/myfile.xlf:my.label.

As mentioned above, the translation files follow the same naming conventions, but are prepended with the language code and a dot. They are stored alongside the default language files.

ID naming

It is recommended to apply the following rules for defining identifiers (the id attribute).

Separate by dots

Use dots to separate logical parts of the identifier.

Good example:

CType.menuAbstract

Bad examples:

CTypeMenuAbstract
CType-menuAbstract

Namespace

Group identifiers together with a useful namespace.

Good example:

CType.menuAbstract

This groups all available content types for content elements by using the same prefix CType..

Bad example:

menuAbstract

Namespaces should be defined by context. menuAbstract.CType could also be a reasonable namespace if the context is about menuAbstract.

lowerCamelCase

Generally, lowerCamelCase should be used:

Good example:

frontendUsers.firstName

Note

For some specific cases where the referenced identifier is in a format other than lowerCamelCase, that format can be used: For example, database table or column names often are written in snake_case, and the XLIFF key then might be something like fe_users.first_name.