New Extension and Platform App APIs

Summary

Chrome exposes special capabilities to Extensions through different APIs. Before implementing a new API, it has to go through an approval process. This approval process helps ensure that the API is well defined, does not introduce any privacy, security, or performance concerns, and fits in with the overall product vision.

API Details

Public or Private

Default: Public

Extension APIs can either be public (available for any extension to potentially use, though frequently there are other constraints like requiring a permission) or private (only available to extensions with a specific allowlisted ID). In general, private APIs should only be used for pieces of functionality internal to Chromium/Chrome itself (e.g., the translation utility, printing, etc). Public APIs should always be the default, in order to foster openness and innovation.

Good reasons for a private API might be:

  • The API is needed by a core feature of Chrome/Chromium. Note that even here, there can be exceptions, if the API could be reasonably implemented as a way to benefit external extensions.

Bad reasons for a private API might be:

  • The API is only needed for a Google property (other than Chrome/Chromium). In the spirit of openness, we should, when possible, provide people with the means to build alternatives. Just because something is needed by a Google property does not mean it wouldn't be useful to a third-party.
  • The API is needed by a Google property (other than Chrome/Chromium), and is too powerful to expose to any third-party extension. Generally, if an API is too powerful to expose to a third-party extension, we don‘t want to expose it to any kind of (non-component) extension, as it increases Chrome’s attack surface. Typically, these security concerns can be addressed by finding alternatives or tweaking the API surface.
  • This is just a quick-and-dirty API and we don't want to go through a long process. Quick-and-dirty hacks have a nasty habit of staying around for years, and often carry with them their own maintenance burdens. It's very frequently cheaper to design an API well and have it be stable than to have a quick solution that has to be constantly fixed.

Unless there is a compelling reason to make an API private, it should default to public.

API Ownership

In general, you (or rather, your team) will own the API you create. The Extensions team does not own every API, nor would it be possible for them to maintain them all. This means that your team will be responsible for maintaining the API going forward.

Platforms

Default: All Desktop Platforms

Extensions are supported on all desktop platforms (Windows, Mac, Linux, ChromeOS, and desktop Android). By default, an extension API will be exposed on all these platforms, but this can be configured to only be exposed on a subset. However, an API should only be restricted if there is strong reason to do so; otherwise, platforms should have parity.

Proposal Process

Starting the review process early is encouraged, and if some of the artifacts are missing or in progress, we‘re happy to work with you on it. It’s better to have us review the API in principle to ensure it‘s something we’re comfortable adding to the platform, and then work out the details, than to invest heavily only to find out that we don't want to add the API to the platform. Feel free to file a bug without everything ready, or to email extension-api-reviews@chromium.org for advice and feedback!

Proposals and Approvals for new APIs should follow these paths based on the applicability.

Public API

Proposed by External (third-party contributor)

  1. Establish interest in WECG -- File an issue or start a discussion in the WebExtensions Community Group (WECG) GitHub repository to gauge community interest and collect feedback.
  2. Identify a sponsoring browser -- Identify a “sponsoring browser” (a browser vendor committed to implementing the API in the near future) prior to submitting the proposal.
  • How to find a Chrome Sponsor: Reach out to extensions-api-reviews@chromium.org or tag known Chromium/Chrome Extension maintainers in your GitHub proposal to find an engineering advocate inside Google.
  1. Submit Proposal in the WECG for API review -- Submit a formal API proposal following the proposal template to the WECG for review. Secure consensus and approval from relevant browser vendors, including Google Chrome.
  2. Launch Reviews & Approvals -- Once WECG consensus is secured, your Google Chrome sponsor will manage the internal review process. Your sponsor will submit the launch ticket and guide your API through cross-functional gates (Security, Privacy, Legal, API Reviewer and DevRel). Be prepared to assist your sponsor with technical details if required.

Proposed by Googlers

(Intended for Googlers working inside Google's Launch / Buganizer environment)

  1. Internal alignment -- Align internally with the Chrome Extensions team (reach out to extension-api-reviews@chromium.org) and relevant stakeholders before public submission. It's recommended to create a draft version of the API proposal following the proposal template before submitting to WECG for internal alignment.
  2. Propose in the WECG for API review -- Submit a formal [API proposal][wecg-propopsal] to the WECG for review. Secure consensus and approval from relevant browser vendors.
  3. Launch Reviews & Approvals -- Once WECG consensus is secured, submit a launch bug adhering to Google's launch standards to complete cross-functional reviews and approvals (Security, Privacy, Legal, UX, Extensions team & DevRel). Review Extensions API Launch Process for details regarding launch workflow and requirements.

Modifying an Existing API

Modifications to an existing API should go through a similar process as the new API proposal process. Since modifications to these APIs are frequently far-reaching, please do not skip the proposal process! However it might be possible to skip or expedite it in certain specific cases. In particular:

  • Small changes (like adding a new property to a method) to private APIs can skip the launch review process unless //extensions OWNERS explicitly ask for it. Small changes to non-private APIs are still required to go through this process (via WECG proposal) but may not require a full design doc or API Overview doc.
  • Medium-sized changes, like adding a single new method, are still required to go through the launch review process. Whether an API overview doc is required is up to the discretion of the API reviewers but inclusion of any supporting documentation is highly recommended.
  • Larger changes, like adding multiple new methods and events, should still submit a formal API proposal to the WECG for review (though it may be condensed).

Private API

  1. Internal alignment -- Align internally within Google to establish the necessity of a private API (e.g., core Chrome features or internal tools). Contact Chrome Extensions team and relevant stakeholders before submission.
  2. Draft API proposal -- Propose and document the API specification using the proposal template in a document.
  3. Launch Reviews & Approvals -- submit a launch bug adhering to Google's launch standards to complete cross-functional reviews and approvals (Security, Privacy, Legal, UX, Extensions team & DevRel). Review Extensions API Launch Process for details regarding launch workflow and requirements.

FAQ

Do I need an API review for a private API? Yes! Private APIs are not as scrutinized as public APIs because we don't need to be as worried about API ergonomics, and we can be a little more lenient in security. However, we still need to review the API to make sure that:

  • The API is secure. Even though it runs in trusted extensions, it exposes capabilities to a renderer process, and may also introduce vulnerabilities elsewhere.
  • The API meets privacy guidelines. We hold ourselves to a strict standard in regards to what data we can collect.
  • The API should be a private API. There are multiple alternatives, including a public API, a web API, implementing code directly in C++, and others. Private APIs are not always the appropriate choice.

How long does the API approval process usually take through Google's launch process?

Securing approvals from all cross-functional stakeholders (Security, Privacy, Legal, DevRel, etc.) typically takes anywhere from 4 to 6 weeks. Highly complex APIs or APIs with broad privacy implications may take longer. We recommend submitting your proposal as early as possible to avoid delaying your launch.

What does “API Ownership” actually mean in practice for my team? Ownership means your team acts as the primary maintainer of the API surface. Responsibilities include triaging incoming bugs related to the API, tracking security/vulnerability upgrades, maintaining test coverage in the Chromium suite, and drafting future modifications.

New API Proposal Process Workflow

Flowchart Diagram for API Proposal Process