#1146: Incubation: Proofreader API

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Opened Sep 4, 2025

I'm requesting an early TAG design review of the writing assistance APIs.

Proofreading is the process of examining a text carefully to find and correct errors such as grammar, spelling, and punctuation to generate an error-free text before it is published or shared. Browsers and operating systems are increasingly offering proofreading capability to help their users compose (examples: Oodles of improvements to Chrome's Spell Checking, Use Writing Tools with Apple Intelligence on Mac). Web applications can also benefit from such proofreading capability backed by language models for a variety of use cases.

We're proposing an API that uses language models to give web developers high-level functionalities for proofreading. Specifically:

  1. Error Correction: Correct input text by the user
  2. Error Labeling: For each correction made to each error in the input text, label the error type (e.g. spelling, punctuation, etc.)
  3. Error Explanation: Annotates each error with a plain language explanation

Explainer

https://github.com/webmachinelearning/proofreader-api/blob/main/README.md

The explainer

Where and by whom is the work is being done?

Feedback so far

  • Multi-stakeholder feedback:
    • Chromium comments: We are excited to start trialing this API with developers through origin trials and behind-a-flag experiments.
    • Mozilla comments:
    • WebKit comments:
    • Web developers:
      • Public feedback on https://github.com/webmachinelearning/proofreader-api/issues was mixed. To summarize, some themes we saw include: asking for more capabilities (e.g. integrating custom dictionaries; adding confidence score to correction output); desire to make sure the API performs efficiently in real-world use cases like proofreading during active editing of the text.

You should also know that...

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Discussions

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Discussed Oct 13, 2025 (See Github)

Christian: Didn’t have a look yet. Matthew: Would need a little bit more time.

Discussed Oct 20, 2025 (See Github)

Christian is not here...

Matthew: I need a bit more time.

Ehsan: Also still reading it. Will post it hopefully next week.

Discussed Oct 27, 2025 (See Github)

Matthew: We are not the experts on these sorts of tools, but we might know people who are. So much fail in the UK.

Christian: Not a domain expert, but it looks fine. Check with domain experts. Shares a lot of features with other AI-related APIs, so it is somewhat blocked by those discussions.

Hadley: i18n we have some choices to make. We could ask the i18n folks to look into this. They can be helpful, but it is a big ask of them. Another option is we could go to a former TAG member with expertise if they want to help out. No one comes to mind. Sangwhan has an interest in i18n because we were messing with his daily life, more than a professional interest. We could say to the group what you said and leave it at that.

Christian: I would prefer to wait on the Prompt API response. A lot of the feedback there applies to Proofreading, especially the model download/initialization part. We should be open about that.

Hadley: Pending external feedback?

Christian: fine.

Matthew wanted to say something about this as well, but he was having connectivity issues.

Matthew: I put in slack that Ehsan has a comment coming, but that's compatible with the above resolution.

Comment by @christianliebel Oct 30, 2025 (See Github)

@QueenieZqq Thanks for your proposal. As it shares parts of its API surface with the Prompt API, we want to finalize the Prompt API review (https://github.com/w3ctag/design-reviews/issues/1093) before proceeding. We will postpone the review of this API until that review is complete.