*Contact emails*
[email protected]

*Explainer*
https://github.com/WICG/js-self-profiling/issues/86

*Specification*
https://wicg.github.io/js-self-profiling/#js-profiling-mode

*Summary*
Introduces a new Document-Policy value "js-profiling-mode=eager|lazy".
Setting "js-profiling-mode=lazy" authorizes JS Self-Profiling capability
without incurring immediate initialization overhead during page load.

*Note: This change doesn't affect the actual feature beyond the default
setting.*

*Blink component*
Blink>PerformanceAPIs
<https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3EPerformanceAPIs%22>

*Web Feature ID*
profiler <https://webstatus.dev/features/profiler>

*Motivation*
*JS Self-Profiling is a pre-existing feature, but currently only supports
eager mode.*

There are several pain points with the current “eager” approach:
1 - Performance trade-offs between loading and profiling

There is no way to defer profiling overhead to a non-critical period (e.g.,
after page load).
There is no way to incur overhead only if the Profiling API is actually
used. Many users are unwilling to trade page load performance for profiling
capabilities.

2 - Sampling strategy coupling between backend (server) and frontend
(client)

To avoid overhead on unsampled sessions, sampling must be aligned between
server and client, which introduces operational complexity.
In many setups, sampling occurs on the client side; keeping server and
client in sync requires additional tooling. Even if a session is not
sampled, the presence of the header means the page still pays the warm-up
cost.

(See https://github.com/WICG/js-self-profiling/issues/86 for full context)

*Initial public proposal*
https://github.com/WICG/js-self-profiling/pull/87

*Requires code in //chrome?*
False

*Tracking bug*
https://issues.chromium.org/issues/473861788?pli=1

*Estimated milestones*

No milestones specified


*Link to entry on the Chrome Platform Status*
https://chromestatus.com/feature/5108831124324352?gate=5074849745731584

This intent message was generated by Chrome Platform Status
<https://chromestatus.com/>.
-- 

Best,

Thomas BERTET

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