Request for Deprecation Trial: Deprecate TLS SHA-1 server signatures

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David Adrian

Jun 8, 2023, 3:53:15 PM6/8/23
to blink-dev, David Benjamin

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Chrome is removing support for signature algorithms using SHA-1 for server signatures during the TLS handshake. This does not affect SHA-1 support in server certificates, which was already removed, or in client certificates, which continues to be supported.

Blink component


Search tags


TAG review


TAG review status

Not applicable


Interoperability and Compatibility

At most 0.02% of page loads use the SHA1 fallback. However, we cannot disambiguate between a flaky first connection, and actually requiring SHA1. We expect the actual amount is lower.

Gecko: No signal (

WebKit: No signal (

Web developers: No signals

Other signals:

WebView application risks

Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?


Goals for experimentation

Since this takes place before a document is loaded, sites cannot opt-in. We plan on doing a 1% stable experiment and monitoring any increase in page load failures and SSL failures.

This experiment is managed via Finch, not as an Origin / Deprecation Trial.

Experiment Risks

Sites that are incapable of SHA2 signatures would fail to load. However, we believe the actual set of sites that don't support SHA2 is very small. Due to how negotiation works in TLS, we can't tell the difference between "prefers SHA1 to SHA2, but has a flaky network" and "only supports SHA1". In the worst case, this is 0.02% of TLS connections. In the best case, this is 0%.

Ongoing technical constraints



n/a, this happens pre-devtools

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)?


Is this feature fully tested by web-platform-tests?


Flag name


Requires code in //chrome?


Tracking bug

Launch bug

Estimated milestones

Shipping on desktop117
OriginTrial desktop last116
OriginTrial desktop first115
DevTrial on desktop115
Shipping on Android117
OriginTrial Android last116
OriginTrial Android first115
DevTrial on Android115
OriginTrial webView last116
OriginTrial webView first115

Link to entry on the Chrome Platform Status

Links to previous Intent discussions

This intent message was generated by Chrome Platform Status.

David Adrian

Jun 8, 2023, 3:54:46 PM6/8/23
to blink-dev, David Benjamin
Per request on the previous thread, converting the previous Ready for Trial to an Intent to Experiment / Request for Deprecation Trial.

Due to the nature of the TLS stack, this experiment will be managed by Finch, rather than site opt-in.

Mike West

Jun 13, 2023, 4:50:19 AM6/13/23
to David Adrian, blink-dev, David Benjamin
Per the conversation on the previous thread, carefully rolling this out to measure breakage seems like the right path forward. Do you have a timeline along which you'd like to run this experiment? M115-M118?


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David Adrian

Jun 13, 2023, 2:31:23 PM6/13/23
to Mike West, blink-dev, David Benjamin
We plan to start in M115. Four milestones seems a bit long---this breakage likely either be immediately evident or a no-op. I was thinking M115 and M116, but we'll defer to your judgement.

Mike West

Jun 13, 2023, 2:46:42 PM6/13/23
to David Adrian, David Benjamin, blink-dev
LGTM to experiment from M115 to M116.

Good luck!

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