Language

Hello please could you provide a screenshot to show which part of the interface you are referring to? You can use imgurl to share.

View post on imgur.com

View post on imgur.com

This problem is not resolved. I only added the image…

Do you wish to keep your site in French, but have WP-Optimize in English?

Exactly!

The plugin by default will display in the language you have set your site to unfortunately.

Where is the “language” file (e.g. “fr_FR.mo”)?
If I delete it (via FTP) then the plugin should switch back to its default English version…

It’s WordPress core, not individual plugins, that control overall language. Language files are in wp-content/languages. If you delete it and find that it comes back later, then this means WordPress core re-downloaded it (I’m not an expert on what conditions that happens under).

Looking at the code, I guess it is using WordPress language features, which explains the choice of the same language as the WordPress installation. I am not going to try to modify the code as it would create difficulties when updating…