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Add more documentation for sizes=auto#39464

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Josh-Cena merged 12 commits intomdn:mainfrom
tunetheweb:img-sizes-auto
May 13, 2025
Merged

Add more documentation for sizes=auto#39464
Josh-Cena merged 12 commits intomdn:mainfrom
tunetheweb:img-sizes-auto

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@tunetheweb tunetheweb commented May 9, 2025

Description

Add sizes=auto description to htmlimgageelement doc and add extra note to equivalent <img> doc (where it is documented already).

Motivation

New feature that is underdocumented.

Additional details

https://chromestatus.com/feature/5191555708616704
https://ericportis.com/posts/2023/auto-sizes-pretty-much-requires-width-and-height/

Related issues and pull requests

Was added to BCD in: mdn/browser-compat-data#23785

Was also partially added in #38025

Fixes #30596

@tunetheweb tunetheweb requested review from a team as code owners May 9, 2025 07:04
@tunetheweb tunetheweb requested review from estelle and wbamberg and removed request for a team May 9, 2025 07:04
@github-actions github-actions bot added Content:HTML Hypertext Markup Language docs Content:WebAPI Web API docs size/s [PR only] 6-50 LoC changed labels May 9, 2025
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github-actions bot commented May 9, 2025

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External URLs (1)

URL: /en-US/docs/Web/HTML/Reference/Elements/img
Title: <img>: The Image Embed element

(comment last updated: 2025-05-12 23:59:34)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
tunetheweb and others added 2 commits May 9, 2025 12:44
Comment on lines +31 to +33
- `auto`

- : You can use the value `auto` to replace the whole list of sizes or the first entry in the list. It is only valid when combined with `loading="lazy"`, and resolves to the [concrete size](/en-US/docs/Web/CSS/image) of the image. Since the intrinsic size of the image is not yet known, `width` and `height` attributes (or CSS equivalents) should also be specified to [prevent the browser assuming a default width of 300px](https://html.spec.whatwg.org/multipage/images.html#sizes-attributes:~:text=it%20is%20strongly%20encouraged%20to%20specify%20dimensions%20using%20the%20width%20and%20height%20attributes).
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@Josh-Cena Josh-Cena May 9, 2025

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Suggestion: do not duplicate information about the precise attribute value syntax. This entire "Value" section could be replaced with something like "A string containing a comma-separated list of source size descriptors. For the exact syntax and description, see the [HTML reference](link)".

(Edit: actually we already do that. If you think it's confusing to mention some syntax but not others, IMO we should just remove everything.)

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It's a bit confusing as this page gives a brief summary of the syntax, and then a link. So think it is worthwhile to mention that auto is now supported. However, I cut it down to a single sentence. PTAL.

@tunetheweb tunetheweb requested a review from Josh-Cena May 12, 2025 23:57
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Looks great. Thank you!

@Josh-Cena Josh-Cena merged commit bd6d5e5 into mdn:main May 13, 2025
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wbamberg added a commit to wbamberg/content that referenced this pull request May 21, 2025
* upstream/main: (40 commits)
  Add a guide on xs-leaks (mdn#38977)
  chore: Link to child pages in SVG, URI section (mdn#39470)
  Correct page title for `Uint8Array.prototype.setFromHex()` (mdn#39494)
  Bump markdownlint-cli2 from 0.17.2 to 0.18.0 (mdn#39488)
  Add more documentation for sizes=auto (mdn#39464)
  css(fix): update 'shape()' page (mdn#39454)
  Expand Compression Dictionary format description (mdn#39441)
  Add username/password section to URLs guide (mdn#39487)
  Fix typos (mdn#39481)
  CSS: mask-position property description (mdn#39449)
  Adding @starting-style to CSS nesting at-rules (mdn#39473)
  feat(aria): Add short titles, format titles for roles (mdn#39472)
  Fix Circle Collision detection algorithm (mdn#39484)
  Add warning against using element IDs as global properties. (mdn#39422)
  Fix typos in web audio spatialization basics (mdn#39476)
  More Error Messages (mdn#39419)
  Add links to CSS sidebar (mdn#39445)
  css: add 'stretch' value examples (mdn#39451)
  chore: link to unlinked child pages (mdn#39469)
  Fix typos (mdn#39465)
  ...
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Document img auto-sizes

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