While looking at the Google Search Console, I noticed that some wikis were prevalent in URLs that get "poor" ratings (eg. > 4 seconds for p75 Largest Contentful Paint). This is easily explained by the fact that speakers of those languages tend to live in areas where internet connectivity is poor.

Wiki-local file pages in particular come up in a lot in those:

I think it's clear that for visitors of those wikis, bad internet connectivity and they could benefit of lot from webp thumbnails. It's also likely that the traffic on those wikis is too low for most of their images to ever hit the current webp threshold.

This is also a good test to see if we can positively influence URLs that are currently marked as "poor" by Google.

Based on the Search Console data, it would make sense to enable webp for all images hosted on the following wikis:

• sw which hosts around 2000 media files
• tg 400
• tk 300
• bcl 800
• war 40
• mai 100
• or 100
• bh 50
• zh 47000

But, honestly, seeing how low these numbers are, I think we can actually afford to do this for every non-Commons wiki. Maybe with the exception of enwiki, which is an outlier with close to 1 million media files. dewiki has 120k, jawiki 70k, frwiki 60k, etc.

Of course we can start with an allowlist initially and roll the change out gradually.