Wikimedia thumbnail URLs are based on width only. Scaling maintains the original ratio.
AntiCompositeNumber (they/them) On Fri, Jan 23, 2026, at 13:41, Travis Briggs wrote: > Hi Amir, > > Thanks for the heads up on this. I'm confused about the idea of > standard "sizes", as listed. Thumbnails have two dimensions, two sizes, > width and height right? Do both dimensions have to be one of the > standard sizes? What if that causes image stretching? > > Thanks, > -Travis > > On Fri, Jan 23, 2026 at 10:28 AM Amir Sarabadani via Wikitech-l > <[email protected]> wrote: >> Thumbnails shown on-wiki are already quantized to a set of standard sizes >> (if a non-standard size is requested, the next-larger standard size is used, >> and scaled to the requested size by the browser). We have recently extended >> the set of standard sizes, and are now moving to only allow standard sizes >> to be used. Regular editing and viewing will not be impacted by this change >> at all. >> >> * What isn't changing? >> >> Thumbnails served on wiki (via the "thumb" argument to File:, and via the >> Media API) will continue to behave as they do now - if you request a >> non-standard size, the next-larger standard size will be provided, and >> scaled in-browser if appropriate. >> >> * What is changing? >> >> Requests for non-standard thumbnail sizes using other methods (e.g. >> constructing an upload.wikimedia.org URL with a non-standard thumbnail size) >> will be blocked by our CDN. These are already being rate-limited for >> requests that we assess are not coming from a web-browser. >> >> During this quarter, we will be broadening the scope of the existing >> rate-limiting and making it increasingly strict, with the aim being to >> refuse such requests entirely by the end of March 2026. >> >> * Why are WMF doing this? >> >> Historically, we have generated thumbnails of whatever size was requested; >> this has been a drain on our thumbnailing infrastructure and cost us in >> network bandwidth and storage volume. With the increasing prevalence of >> highly aggressive scrapers, this has become an intolerable burden on our >> network, infrastructure, and staff, who have spent a lot of time over the >> holiday period working hard to keep the wikis available for people to read >> in the face of automated abuse. >> >> * What do I need to do? >> >> Most likely, nothing: we have already tracked down some of the more >> widely-deployed sources of nonstandard thumbnail requests (e.g. Popups >> extension) and fixed them. If you own or operate something that requests >> thumbnails by constructing a thumbnail URI directly, then now is the time to >> either use the Media API instead or to make sure you only request standard >> thumbnail sizes. >> >> * What are the standard thumbnail sizes? >> >> They are: 20px, 40px, 60px, 120px, 250px, 330px, 500px, 960px, 1280px, >> 1920px, 3840px >> >> They are defined in config as $wgThumbnailSteps - >> https://gerrit.wikimedia.org/r/plugins/gitiles/operations/mediawiki-config/+/refs/heads/master/wmf-config/CommonSettings.php >> >> And also documented on MetaWiki - >> https://www.mediawiki.org/wiki/Common_thumbnail_sizes >> >> To help fix the existing instances, please see >> https://phabricator.wikimedia.org/T414805 for search-links, and examples of >> how to fix them. >> >> Best >> -- >> *Amir Sarabadani (he/him)* >> Staff Database Architect >> Wikimedia Foundation <https://wikimediafoundation.org/> >> >> _______________________________________________ >> Wikitech-l mailing list -- [email protected] >> To unsubscribe send an email to [email protected] >> https://lists.wikimedia.org/postorius/lists/wikitech-l.lists.wikimedia.org/ > _______________________________________________ > Wikitech-l mailing list -- [email protected] > To unsubscribe send an email to [email protected] > https://lists.wikimedia.org/postorius/lists/wikitech-l.lists.wikimedia.org/ _______________________________________________ Wikitech-l mailing list -- [email protected] To unsubscribe send an email to [email protected] https://lists.wikimedia.org/postorius/lists/wikitech-l.lists.wikimedia.org/
