The open source web performance tool just shipped 40.0. sitespeed.io, out september 18, adds a new…
the open source web performance tool just shipped 40.0. sitespeed.io, out september 18, adds a new har waterfall, coach rules updated for 2026 and safari on ios support with video.
your slow page now comes with a video.
Context
The sitespeed.io 40.0 post lists a refreshed HTML report, a new HAR waterfall replacing PerfCascade with waterfall-tools, updated Coach rules for 2026 with severity on every rule, an INP rule, four image rules and refreshed thresholds, an improved Browsertime scripting API, and Safari on iOS over USB with HAR and video. It names Browsertime 27 and coach-core 9 as dependency bumps.
The features match the note. The extracted post text is undated, and search snippets of the GitHub release listings show v40.0.0 published 2026-05-05 and v40.1.0 on 2026-05-06, which conflicts with out september 18. The release page text itself was not read, so the date stays unverified either way. Safari on iOS is over USB, with setup requirements not summarized, and no benchmark claims were read. Your slow page now comes with a video is the author's take, and video for other browsers was not examined.
Watch next
- The GitHub release page text for the exact date.
Sources
- sitespeed.io: 40.0sitespeed.io
Provenance
The note above is reproduced unedited from the original post, first published on Threads on 22 September 2026 at 17:43 IST. Sources are the papers and datasets the note draws on.
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