[Resolved] Set Media as "Translatable – use translation if available or fallback to default language"

"On the test site, the media is already synced when being uploaded to the media library in the site's default language."
-> Only because you disabled the "Automatically detect best options for translating image texts" just now. With this option (that is even recommended in a banner now that is disabled!) the media is NOT synced between languages when uploaded to the media library.

It would be much easier if you could just assign a different supporter to this ticket where they already have all the context. But if creating a new support ticket is the only way for me to receive support, I will do that.

I am just quickly reopening this ticket to add the reply I got when creating a new support ticket, in case someone has a similar problem.

This time, I was redirected to WPML's AI assistant (I probably landed on some blacklist 😄). The answer was completely different from what Andreas told me. Of course an AI bot cannot be completely trusted, but I assume it has good training on internal documentation and code. So here is the answer:

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Hi there! I understand you're working with a very large website, managing approximately 1.5 million images with your theme, and aiming for optimal performance by minimizing media duplication. That's a significant setup, and it's great you're thinking proactively about database efficiency.

You've accurately identified that the "Automatically detect best options for translating image texts" setting, while generally recommended for streamlining media translation, can lead to images not appearing in your media library on secondary languages. This often happens because this setting intelligently creates translations of media metadata only when necessary (e.g., when an image is associated with a translated post via the Advanced Translation Editor), rather than duplicating the attachment post itself for every image across all languages.
Your observation that setting the "Attachment" post type to "Use translation if available or fallback to default language" resolves the issue of missing images in secondary language media libraries is correct. This setting is indeed a valid and often optimal approach for sites like yours, where the majority of images don't require distinct translated texts and the primary goal is to ensure their visibility and usability across all languages without unnecessary database duplication.

Let's address your questions about why this option might be behind a lock or not listed as the default recommended option:

"Not Recommended" Context: The WPML documentation generally advises against turning off the "Automatically detect best options for translating image texts" setting and managing all media translation settings manually. This recommendation is primarily to prevent common pitfalls like unnecessary duplication of media texts (alt text, captions, titles) or missing translations if not configured meticulously. However, selecting "Use translation if available or fallback to default language" for the Attachment post type itself is a different, more general post type translation setting. It doesn't mean you're manually configuring every aspect of media text translation, but rather defining the fallback behavior for the attachment post in your media library.

The "Lock": The lock icon indicates that this is an advanced setting that requires a clear understanding of its implications. For many users, the automatic detection is sufficient. But for your specific use case, with 1.5 million images and a strong focus on performance and controlled duplication, this advanced setting is precisely what you need.

There is no technical or functional reason not to use "Use translation if available or fallback to default language" for attachments in your scenario. In fact, it's an excellent solution to achieve your goals of performance and media accessibility. It ensures that if an attachment post doesn't have a specific translation, the default language version will be displayed and selectable, which is exactly what you're looking for.

Here’s how you can set this up for your attachments:
Navigate to WPML → Settings in your WordPress admin dashboard.
Scroll down to the Post Types Translation section.
Locate the Attachments (attachment) post type.
Select the option "Use translation if available or fallback to default language".
Click the Save button at the bottom of the page.

After applying this setting, please verify that your media library in secondary languages now displays the expected images, allowing you to manually create or update pages effectively. This approach aligns perfectly with your site's needs for efficient media handling.

Thank you for continuing to look into this issue Andreas.

I am not sure why you choose this use case as an example for "Fallback" having no effect. What you describe is completely logical and has nothing to do with the "Fallback" setting.
If I translate a post via the WPML translation editor and WPML creates a duplicate for the featured image, the ID of this duplicate is then set as featured image for the translated post. When I manually delete this duplicate in the media library, the ID saved on the translated post points into the void and the featured image is missing of course.

If however I manually create a post in the secondary language using the Gutenberg editor, the "Fallback" setting clearly has an effect:
- Without "Fallback", the media library is empty
- With "Fallback", all images are available and I can use them in my post. Wen saving the post, no duplicates are created in the background, just as it should be.