LGTM1
The only thing I was going to request was already taken care of: pinging
the Mozilla issue and providing a pointer to this thread (since it's
been about a year - maybe their position has evolved).
On 4/1/26 6:57 p.m., Deepti Bogadi wrote:
Contact emails
[email protected], [email protected], [email protected],
[email protected]
Explainer
https://github.com/webmachinelearning/prompt-api/blob/main/README.md
<https://github.com/webmachinelearning/prompt-api/blob/main/README.md>
Specification
http://webmachinelearning.github.io/prompt-api
<http://webmachinelearning.github.io/prompt-api>
Summary
The Prompt API gives web developers direct access to a
browser-provided on-device AI language model. The API design offers
fine-grained control, aligned with cloud API shapes, for progressively
enhancing sites with model interactions tailored to individualized use
cases. This compliments task-based language model APIs (e.g.
Summarizer API), and varied APIs and frameworks for generalized
on-device inference with developer-supplied ML models. The initial
implementation supports text, image, and audio inputs, as well as
response constraints that ensure generated text conforms with
predefined regex and JSON schema formats.
This supports a variety of use cases, from generating image captions
and performing visual searches to transcribing audio, classifying
sound events, generating text following specific instructions, and
extracting information or insights from multimodal source material.
This API has already been shipped in Chrome Extensions; this intent
tracks the shipping on the web. An enterprise policy
GenAILocalFoundationalModelSettings
<https://chromeenterprise.google/policies/#GenAILocalFoundationalModelSettings>is
available to disable the underlying model downloading, which would
render this API unavailable. Enterprise admins can also set the
BuiltInAIAPIsEnabled policy to block Built-In AI API usage, while
still permitting other on-device GenAI features.
Language support log:
*
Chrome M139 and earlier only supported English ('en')
*
Chrome M140 added support for Spanish and Japanese ('es' and 'ja')
Blink component
Blink > AI > Prompt
<https://issues.chromium.org/issues?q=customfield1222907:%22Blink%20%3E%20AI%20%3E%20Prompt%22>
Web Feature ID
https://github.com/web-platform-dx/web-features/issues/3530
Motivation
Direct access to a language model can help web developers accomplish
tasks beyond those with dedicated APIs (e.g. Summarizer API) , and
tailor their usage for site-specific requirements. Compared to the
low-level APIs approach (e.g a custom AI model run via WebGPU, WASM,
or WebNN), using the built-in language model can save the user's
bandwidth and disk space, and has a lower barrier to entry. The design
offers simple shorthands for common patterns (e.g. await
session.prompt(‘write a haiku’)), and supports more complex use cases
for handling structured content sequences, streaming responses,
availability checks, session management, and response constraints.
Initial public proposal
https://github.com/webmachinelearning/charter/pull/9
<https://github.com/webmachinelearning/charter/pull/9>
Search tags
LanguageModel <https://chromestatus.com/features#tags:LanguageModel>,
Language Model
<https://chromestatus.com/features#tags:Language%20Model>, Prompt API,
Built-in AI
TAG review
https://github.com/w3ctag/design-reviews/issues/1093
<https://github.com/w3ctag/design-reviews/issues/1093>
TAG review status
Issues addressed
WebFeature UseCounter name
kLanguageModel_Create
Risks
Interoperability and Compatibility
The Prompt API is designed to provide a stable and interoperable
surface for language model interactions, acknowledging the inherent
diversity and non-deterministic nature of underlying models. Variance
in behaviors and responses is a well understood expectation amongst
developers employing this technology, and this API aims to provide an
interoperable framework for consistent web platform access across
browsers and models.
The Prompt API specifically aims to maximize compatibility by:
- Codifying an interoperable API surface for generalized language
model interactions, so developers can write code that works across
different browser engines and models. This surface has demonstrated
compatibility with models from Google and Microsoft, and been
polyfilled by extensions and JS frameworks, using different backends.
- Enforcing objective response conformance with constraints that
ensure output adheres to known JSON schemas or regexes for
interoperable processing of generated text.
- Supporting progressive enhancement patterns, by offering
availability signals that encapsulate device and model support
dimensions, and encourage developers to consider this API as one
option among varied compatible AI offerings, including developer
supplied models and cloud-based services.
Shipping this API provides a critical opportunity to broaden
real-world implementation experience, explore future refinements, and
collaborate with the web community on interoperable model diversity
within a robust, predictable platform surface.
Gecko: Negative
(https://github.com/mozilla/standards-positions/issues/1213
<https://github.com/mozilla/standards-positions/issues/1213>)
WebKit: No signal
(https://github.com/WebKit/standards-positions/issues/495
<https://github.com/WebKit/standards-positions/issues/495>)
Web developers: Strongly positive
(https://github.com/webmachinelearning/prompt-api/blob/main/README.md#stakeholder-feedback
<https://github.com/webmachinelearning/prompt-api/blob/main/README.md#stakeholder-feedback>)
Other signals: Microsoft Edge developers have been strong
collaborators with notable contributions including structured output,
and experimental tool use enhancements. Edge will be shipping this API
using a different underlying model.
Ergonomics
The API deprecated parameters and renamed identifiers, leaving legacy
access for previously launched extension contexts. We plan to align
the web and extension surfaces through careful additive changes and
cautious deprecation processes. Developers are encouraged to use the
new identifier names in both contexts and observe deprecation messages
regarding planned API alignments.
Activation
This feature would definitely benefit from having polyfills
<https://www.npmjs.com/package/prompt-api-polyfill>, backed by any of:
cloud services, lazily-loaded client-side models using
WebGPU/WASM/WebNN, or the web developer's own server. We anticipate
seeing an ecosystem of polyfills and client frameworks grow as more
developers experiment with this API.
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?
Not Applicable; this API is not available in WebView.
Debuggability
The API surface supports basic DevTools debugging. Perfetto tracing
(via optimization_guide and other events) is useful, and internal
debugging pages which give more detail on the model's status, e.g.
chrome://on-device-internals might be suitable to port into DevTools.
The team is maintaining extensions
<https://chromewebstore.google.com/detail/webai-extension/lmjgpcigjcffnphimblhcoccjfefamcp>of
DevTools panels for improving debuggability. It is possible that
giving more insight into the nondeterministic states of the model,
e.g. random seeds, could help with debugging.
Will this feature be supported on all six Blink platforms (Windows,
Mac, Linux, ChromeOS, Android, and Android WebView)?
No
The initial launch focuses on Windows, Mac, Linux, and ChromeOS
(onChromebook Plus
<https://www.google.com/chromebook/chromebookplus/>devices). An
implementation for Android using that platform’s OS-level built-in
language model is being prototyped and will ship after the initial launch.
Is this feature fully tested by web-platform-tests
<https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?
No
Web platform tests cover the API surface adequately:
https://wpt.fyi/results/ai/language-model
<https://wpt.fyi/results/ai/language-model>These attempt to mitigate
execution environments differences, e.g. stub/full implementations
(content_shell, chrome), and device/model states (unavailable,
downloadable, downloaded). The core responses of real models can be
unpredictable (especially without sampling parameters) and may cause
inconsistent test results, but some facets are more readily testable,
e.g. the adherence to structured output response constraints. Test
coverage and reliability improvements are ongoing, including planning
for WebDriver extensions.
DevTrial instructions
https://developer.chrome.com/docs/ai/prompt-api
<https://developer.chrome.com/docs/ai/prompt-api>
Flag name on about://flags
prompt-api-for-gemini-nano-multimodal-input
Finch feature name
AIPromptAPIMultimodalInput
Rollout plan
Will ship enabled for all users
Requires code in //chrome?
True
Tracking bug
https://crbug.com/417526788 <https://crbug.com/417526788>
Launch bug
https://launch.corp.google.com/launch/4461863
<https://launch.corp.google.com/launch/4461863>
Measurement
The API has use counters for all methods and attributes e.g.:
LanguageModel_Create LanguageModel_Availability LanguageModel_Prompt
LanguageModel_PromptStreaming LanguageModel_Append
LanguageModel_MeasureContextUsage LanguageModel_OnContextOverflow
LanguageModel_ContextUsage LanguageModel_ContextWindow
LanguageModel_Clone LanguageModel_Destroy
Non-OSS dependencies
Does the feature depend on any code or APIs outside the Chromium open
source repository and its open-source dependencies to function?
Yes: this feature depends on a language model, which is bridged to the
open-source parts of the implementation via the interfaces in
//services/on_device_model.
Estimated milestones
Shipping on desktop
148
Origin trial desktop first
139
Origin trial desktop last
144
Origin trial extension 1 end milestone
147
DevTrial on desktop
137
Anticipated spec changes
Open questions about a feature may be a source of future web compat or
interop issues. Please list open issues (e.g. links to known github
issues in the project for the feature specification) whose resolution
may introduce web compat/interop risk (e.g., changing to naming or
structure of the API in a non-backward-compatible way).
Params may be re-added after addressing interop concerns:
https://github.com/webmachinelearning/prompt-api/issues/170
<https://github.com/webmachinelearning/prompt-api/issues/170>Identifiers
have been renamed for clarity before Web GA launch:
https://github.com/webmachinelearning/prompt-api/issues/177
<https://github.com/webmachinelearning/prompt-api/issues/177>Any
post-launch additive changes should be backwards compatible: e.g. tool
use, multimodal sampling info/options and outputs, session history
access, model info/options, etc.
Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/5134603979063296?gate=5123192519393280
<https://chromestatus.com/feature/5134603979063296?gate=5123192519393280>
Links to previous Intent discussions
Intent to Prototype:
https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM0wra_LXU8KkcVJ0x%3DzYa4h_sC3FaHGdaoM59FNwwtRAsOALQ%40mail.gmail.com
<https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM0wra_LXU8KkcVJ0x%3DzYa4h_sC3FaHGdaoM59FNwwtRAsOALQ%40mail.gmail.com>
Intent to Experiment:
https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM0wra9oT0jygAYT00WPp0_wtZ-znrB2OdZ6GQb%2B3thFLP19pA%40mail.gmail.com
<https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM0wra9oT0jygAYT00WPp0_wtZ-znrB2OdZ6GQb%2B3thFLP19pA%40mail.gmail.com>
Intent to Extend Experiment 1:
https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAJcT_ZhyheBntZHMEwFJA%3DuhpkWmDx8yFieL5E5g%2Bwp5UA0mzQ%40mail.gmail.com
<https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAJcT_ZhyheBntZHMEwFJA%3DuhpkWmDx8yFieL5E5g%2Bwp5UA0mzQ%40mail.gmail.com>
This intent message was generated by Chrome Platform Status
<https://chromestatus.com/>.
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