YouTube page load is 5x slower in Firefox and Edge than in Chrome because YouTube's Polymer redesign relies on the deprecated Shadow DOM v0 API only implemented in Chrome. You can restore YouTube's faster pre-Polymer design with this Firefox extension:https://addons.mozilla.org/firefox/addon/youtube-classic …
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YouTube serves a Shadow DOM polyfill to Firefox and Edge that is, unsurprisingly, slower than Chrome's native implementation. On my laptop, initial page load takes 5 seconds with the polyfill vs 1 without. Subsequent page navigation perf is comparable.
4 replies 77 retweets 229 likesShow this thread -
Replying to @cpeterso
Hey Chris, Happy to discuss in DMs if you're available. Complex situation, large codebase, but team is committed to V1 support.
1 reply 2 retweets 13 likes -
Replying to @slightlylate
Thanks, Alex! I've heard back from someone on the Polymer team who shared more details: IIUC, Polymer 2.x and 3.x should be compatible with Firefox's native implementation of Shadow DOM V1 (coming in Firefox 63, fingers crossed), though YouTube is still using Polymer 1.x and V0.
1 reply 0 retweets 8 likes -
Replying to @cpeterso
That's correct. Note that YT *is* using polyfills, but not Shadow DOM V0; instead it's using Polymer's Shady DOM everywhere at the moment: https://www.polymer-project.org/blog/shadydom
2 replies 2 retweets 18 likes
So things will get faster when everyone moves to V1, which is in progress, but it's not (just) about Shadow DOM.
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