[w3ctag/design-reviews] WG Revision: Web Speech API: SpeechRecognitionResult Timestamps (Issue #1267)

alan33d created an issue (w3ctag/design-reviews#1267)

### Specification

https://github.com/WebAudio/web-speech-api/pull/192

### Explainer

https://github.com/WebAudio/web-speech-api/blob/main/explainers/speech-recognition-result-timestamps.md

### Links

- The WG's request for this TAG review: https://github.com/WebAudio/web-speech-api/issues/191
- TAG review of the previous version of this specification, if any:
  - https://github.com/w3ctag/design-reviews/issues/1093 (MediaStreamTrack input)
  - https://github.com/w3ctag/design-reviews/issues/1146 (On-device speech recognition options)
- A description of what has changed since our previous review: https://github.com/WebAudio/web-speech-api/pull/192

Feature 1:
- Previous early design review, if any: N/A
- An introduction to the feature, aimed at unfamiliar audiences: https://github.com/WebAudio/web-speech-api/blob/main/explainers/speech-recognition-result-timestamps.md
- A description of the problems that end-users were facing before this proposal: https://github.com/WebAudio/web-speech-api/blob/main/explainers/speech-recognition-result-timestamps.md#problem
- Alternatives considered: https://github.com/WebAudio/web-speech-api/blob/main/explainers/speech-recognition-result-timestamps.md#alternatives-considered
- Examples of how to use the proposal to solve the end-users' problems: https://github.com/WebAudio/web-speech-api/blob/main/explainers/speech-recognition-result-timestamps.md#proposed-behavior--example-usage
- What do the end-users experience with this proposal: End users experience synchronized, real-time captions and translated subtitles during live video conferencing and media playback. Web applications can detect when on-device ASR models lag behind real-time on resource-constrained devices and automatically transition to cloud backends without user disruption.
- User research you did to validate the problem and/or design, if any: Live conferencing latency studies and interactive validation demo: https://michaelwasserman.github.io/web-speech-demos/speech_latency_h.html
- Web Platform Tests: https://github.com/web-platform-tests/wpt/tree/master/speech-api (specifically `idlharness.https.window.js` and `SpeechRecognition-onresult-manual.https.html`)

### The specification

- [x] Follows the [Web Platform Design Principles](https://www.w3.org/TR/design-principles/).
- [x] Includes Security and Privacy Considerations sections based on answers to the [Security/Privacy Questionnaire](https://www.w3.org/TR/security-privacy-questionnaire/).

### Where and by whom is the work is being done?

- GitHub repo: https://github.com/WebAudio/web-speech-api
- Primary contacts:
  - Alan Ding (@alan33d), Google, Spec Editor / Implementer
  - Evan Liu (@evanbliu), Google, Spec Editor
  - Paul Adenot (@padenot), Mozilla, WebAudio WG Member / Spec Editor
  - Hongchan Choi (@hoch), Google, WebAudio WG Member / Spec Editor
- Organization/project driving the specification: Google / Chromium
- This work is being funded by: Google
- Primary standards group developing this feature: Audio Working Group (WebAudio WG) / Audio Community Group (AudioCG)
- Incubation and standards groups that have discussed the design:
  - Audio Working Group: https://github.com/WebAudio/web-speech-api/issues/191, https://github.com/WebAudio/web-speech-api/pull/192


### Feedback so far

- Active horizontal reviews: https://github.com/WebAudio/web-speech-api/blob/main/explainers/speech-recognition-result-timestamps.md#security-and-privacy-considerations
- Multi-stakeholder feedback:
  - Chromium comments: Positive / In active development (https://chromestatus.com/feature/5811907077472256)
  - Mozilla comments: Active discussion in https://github.com/WebAudio/web-speech-api/issues/191 and https://github.com/WebAudio/web-speech-api/pull/192#discussion_r3774155900 by @padenot (provided guidance on using `double` in seconds and non-nullable attributes to match Web Audio conventions).
  - WebKit comments: Standards position to be filed at https://github.com/WebKit/standards-positions/
- Major unresolved issues with or opposition to this specification: None. Consensus reached on using non-nullable `double` representing seconds relative to audio stream start.
- Status/issue trackers for implementations:
  - Chrome Status: https://chromestatus.com/feature/5811907077472256
  - Chromium Issue Tracker: https://issues.chromium.org/issues/528037568

### You should also know that...

**W3C Audio WG/CG Meeting Discussion:** This feature was presented and discussed during the **W3C Audio WG/CG Teleconference on August 13, 2026** (see [Meeting Minutes](https://docs.google.com/document/d/1pH4qzMoMTUDYtxW2LDIWKlHfiDeWwctM6s_I78WJzdE/edit?tab=t.ssvip9178d1u)). The group aligned on developer needs for audio timeline association and on-device ASR latency tracking (e.g. enabling optional failover to a cloud ASR provider, to prevent stale or delayed captions in live video conferencing).
- Mozilla's feedback in PRs were also discussed and addressed during the meeting.
- An interactive demonstration showcasing real-time latency calculation, subtitle synchronization, and the inadequacy of existing coarse DOM event timestamps was also presented at the WG meeting. The demo is available at: https://michaelwasserman.github.io/web-speech-demos/speech_latency_h.html

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