Background
This change only impacts logged in users who have selected a thumbnail preference other than 250px in user preferences.
Historically, MediaWiki has allowed users to choose between a variety of thumbnail sizes.
On most wikis the options have been: [ 120, 150, 180, 200, 220, 250, 300, 400 ] with the exception of sv.wikipedia.org which used [ 120, 200, 250, 300, 360 ] and Italian Wikiquote which also supports the additional 360px option.
Why
In an effort to manage the excessive demands spidering has placed on our thumbnail service, we've been making changes to how we serve thumbnails and improving performance for logged in users Each of these thumbnail options requires us to store an additional variant of the article (in parser cache) and means your page is more likely to load slower (given the cache has fewer users). We have recently improved this preference so that it doesn't rely on cache. Part of those efforts involved not splitting the cache on thumbnail size and instead serving the same HTML to all users and managing thumbnail size preferences on the client side.
We will be reducing available options to three T417513: Switch to CSS/JS solution for thumbnail size in legacy parser.
The three options going forward will be:
- Small - 180px
- Regular - 250px
- Large - 400px
During the switchover period, your preferences dropdown will initially look the same
- If you chose a thumbnail size under 250px you will be given Small
- If you chose a thumbnail size is 250px you will be given Regular
- If you chose a thumbnail size is greater than 250px you will be given Large
These options have been carefully selected reviewing historic values and usage patterns in T376152: Evaluate feasibility of deprecating (or limiting) user media size preferences.
How am I impacted
As part of these changes, next week you will notice the following changes:
If you have selected one of the following options, thumbnails will now render at 180px:
120px, 150px, 200px, 220px
If you have selected one of the following options, thumbnails will now render at 400px:
300px, 360px
Next steps
We will be updating Special:Preferences to reflect three options to reduce any confusion that may arise from having different thumbnail sizes from the ones you have chosen explicitly. This work is being done in {TBC}.
How do I opt out?
If this is a problem for you, you can adjust your preferred thumbnail size with CSS (at your own risk) using Special:MyPage/common.css.
If you want to revert back to a 120px thumbnail, make sure your image thumbnail preference is set to 250px and add the following CSS:
.mw-parser-output .mw-default-size img.mw-file-upright,
.mw-parser-output .mw-default-size img[width="250"] {
width: calc(120px * var(--mw-file-upright, 1));
}
