Translation and multilingual plugins

Different translation plugins use different methods for storing the translations, and these methods have varying compatibility with how Relevanssi works with the posts.

Best compatibility

Polylang. Relevanssi has good built-in support for Polylang. This is the best translation tool that causes the least trouble.
WPML. Good built-in support, almost as good as Polylang. WPML is more prone to causing weird edge case problems.

Unknown

Multilingualpress. I don’t know how Multilingualpress works exactly, but based on their documentation it seems the translations are stored in separate posts. That suggests it works like Polylang and WPML and would be compatible.

Not compatible

TranslatePress. The translated strings are stored in a separate database, and are invisible for Relevanssi. It is possible to make Relevanssi index the translated strings, but then Relevanssi has no way to index different languages separately. You can’t restrict the search to a specific language; all languages are mixed together.
GTranslate. The translations are not stored locally at your site, so Relevanssi can’t access them.

WPML: Indexing synced posts

When a post is updated, WPML updates all the translations of the post, but Relevanssi only indexes the post that was updated, not the corresponding posts in other languages. This method hooks into sav...

WPML: Replacing posts with translations

Here's a different approach to WPML searching. By default, you have two options. You can include posts in all languages in the results, or you can only use the current language. This solution check...

Premium 2.12 / Free 4.10

This version started as a small update to 2.11 and 4.9, but then a customer request made me add a major enough feature to warrant a bigger version number update. The big new feature in this version...

Polylang attachment searching

If Polylang is in use and you haven't enabled "Media translation", your attachment files won't have a language. That's fine, except when Relevanssi searches fail to find your attachment because they'r...

Polylang: Bilingual search

By default, Relevanssi indexes the different language versions of the posts separately. If your site is in French and English, searching for the English text will find the English posts and searching ...

WPML: Category exclusions

Relevanssi category exclusion setting doesn't work properly with WPML. Here's a bit of code from Srdjan Jocić from OnTheGoSystems that fixes it. Just add this to your theme functions.php. add_filte...