Web Platform Tests for HTML video element lazy loading via the loading attribute #57051
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…g attribute These tests support the proposal for the addition of a loading attribute on the video element, designed to enable lazy-loading for video and poster data. HTML Standard PR here whatwg/html#11980 Co-authored-by: Zach Lysobey <[email protected]> Co-authored-by: Brad Frost <[email protected]> Co-authored-by: Credo Duarte <[email protected]>
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…d with a proposed HTML feature
rename files to use a .tentative.html convention since they correspond with a proposed HTML feature
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Renamed the files to be |
zcorpan
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Jan 14, 2026
html/semantics/embedded-content/the-video-element/video-loading-attr-default.tentative.html
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.../semantics/embedded-content/the-video-element/video-loading-autoplay-deferred.tentative.html
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.../semantics/embedded-content/the-video-element/video-loading-autoplay-deferred.tentative.html
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html/semantics/embedded-content/the-video-element/video-loading-eager.tentative.html
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.../semantics/embedded-content/the-video-element/video-loading-autoplay-deferred.tentative.html
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html/semantics/embedded-content/the-video-element/video-loading-lazy-in-viewport.tentative.html
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html/semantics/embedded-content/the-video-element/video-loading-lazy-in-viewport.tentative.html
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...ics/embedded-content/the-video-element/video-loading-lazy-poster-when-visible.tentative.html
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...semantics/embedded-content/the-video-element/video-loading-lazy-window-onload.tentative.html
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… event and added a fallback if event never fires.
…t event comes after window load
… scscroll, as the poster image will impact its rendered size and be useful as a proxy for poster lazy loading
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Thanks for the review.
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zcorpan
requested changes
Jan 16, 2026
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| const video = document.getElementById("target"); | ||
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| video.addEventListener("loadstart", () => { |
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Having the video element in markup and adding a listener in a script afterwards can miss the event. Either create the video in script or have a capturing listener before the video element exists.
(Same in some other tests.)
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| <script> | ||
| const belowViewportVideo = document.getElementById("below_viewport"); | ||
| let dataLoaded = false; |
| t.step_timeout(() => { | ||
| t.step(() => { | ||
| assert_greater_than( | ||
| performance.getEntriesByName(url2).length, |
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This test still uses performance.getEntriesByName
| const video = document.getElementById("target"); | ||
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| t.step_timeout(() => { | ||
| t.step(() => { |
| const video = document.getElementById("target"); | ||
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| t.step_timeout(() => { | ||
| t.step(() => { |
| const posterUrl = new URL(video.poster, location.href).href; | ||
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| t.step_timeout(() => { | ||
| t.step(() => { |
| video2.removeAttribute("loading"); | ||
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| t.step_timeout(() => { | ||
| t.step(() => { |
| video.scrollIntoView(); | ||
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| t.step_timeout(() => { | ||
| t.step(() => { |
| video.scrollIntoView(); | ||
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| t.step_timeout(() => { | ||
| t.step(() => { |
| // Change loading to eager - should trigger load | ||
| video1.loading = "eager"; | ||
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| t.step_timeout(() => { |
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Use events instead of timeout here
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These tests support the proposal for the addition of a loading attribute
on the video element, designed to enable lazy-loading for video and poster
data.
Related HTML Standard Proposal: whatwg/html#11980
Related issue: whatwg/html#10376
These are designed to pass in a browser that supports the proposed feature (verified in a locally patched browser).
Co-authored-by: Zach Lysobey [email protected]
Co-authored-by: Brad Frost [email protected]
Co-authored-by: Credo Duarte [email protected]