If you're a developer who likes ProWritingAid's reports and wants those corrections inside your own product, you've probably searched for a ProWritingAid API and found… fragments. A blog post mentioning an API waitlist. A page about integrations that turn out to be Word add-ins and browser extensions. Nothing you can POST text to and get structured edits back from.
The short answer: ProWritingAid does not offer a public grammar-correction API. There is no documented endpoint, no developer dashboard with API keys, no per-character pricing page for programmatic access. What exists instead are consumer integrations (Word, Google Docs, Scrivener, browsers) and a business tier that is still a seat license, not an API.
A disclosure up front: we build AmberPen, a proofreading API, so we have an obvious interest in this answer. We benchmark grammar engines for a living and publish the results. Where ProWritingAid's product genuinely wins, we say so below — it's an excellent consumer tool. It just isn't a developer tool.
What ProWritingAid actually offers developers
ProWritingAid's integration story is real — it's just aimed at writers, not products:
- Desktop and add-in integrations: Microsoft Word, Google Docs, Scrivener, Final Draft, and browser extensions for Chrome, Edge, Firefox, and Safari. These embed ProWritingAid's UI into someone else's editor.
- ProWritingAid Everywhere / business plans: per-seat licenses that make the assistant available across a team's apps. Still no programmatic access — you're buying seats of their interface.
- No public correction endpoint: as of August 2026, ProWritingAid has no documented REST API that accepts text and returns corrections. Older forum threads and a long-dormant API waitlist page are the only traces, and neither has produced a developer product.
This is the same wall developers hit with Grammarly, which we documented in what Grammarly's API actually offers: the consumer assistants have developer programs, but none of them return the thing a product needs — structured grammar corrections with offsets you can render in your own UI.
Why consumer assistants don't sell their engines
It's worth understanding why, because it tells you this is a category, not an oversight. ProWritingAid and Grammarly monetize attention inside their interface: the suggestions card, the score, the upsell to premium. Exposing the engine as an API would let you build a competing interface on top of it — so they don't. The APIs that do exist in this space (scores, license management, enterprise SSO) are designed to sell more seats, not to power your product.
If you want corrections as data, you're shopping in a different category: proofreading APIs — services whose entire product is the endpoint.
The proofreading APIs that actually return corrections
These are the options developers evaluate when the requirement is "send text, receive structured edits":
| API | Engine | Structured edits | p50 latency | Pricing model |
|---|---|---|---|---|
| AmberPen | Neural | Yes, UTF-16 offsets + explanations | 217 ms | Flat per character |
| Sapling | Neural | Yes | 620 ms | Per character, volume tiers |
| GrammarBot Neural | Neural | Yes | 1,000 ms | Usage-based |
| LanguageTool | Rules + statistical | Yes | 287 ms | Free tier, premium, self-hosted |
| Harper | Rules, local | Via library | ~2 ms (in-process) | Free, open source |
Latency figures are from our benchmark runs over identical inputs in July 2026. Harper runs in-process, so its number excludes any network round trip.
A few honest notes on each:
- Sapling is the closest architectural match to AmberPen — send text, get edits with offsets. It scored 0.470 GLEU on JFLEG (best of the rest in our tests), but its CWEB precision of 23.6% means more than three of every four edits it proposed on web text didn't match a human annotation. Details in the AmberPen vs Sapling comparison.
- GrammarBot Neural posted the strongest CWEB precision (40.8%) — the most restrained suggestion stream we measured — but trailed on fluency and was the slowest hosted API at a 1,000 ms median. Fine for batch, noticeable in an as-you-type UI.
- LanguageTool is the pragmatic free option: fast (287 ms), self-hostable, multilingual — but rule-based, so it found 18.3% of the errors human annotators marked in web text. An error no rule anticipates is invisible to it.
- Harper runs entirely locally at ~2 ms. The trade-off is quality: 13.8% recall at 5.8% precision on CWEB, with a characteristic habit of rewriting unfamiliar names into common dictionary words.
Where ProWritingAid genuinely wins
None of this means ProWritingAid is a weak product — it isn't. If you are a writer (especially a novelist or long-form author), its reports on pacing, dialogue tags, sentence-length variety, and overused words are deeper than anything the API category produces, because those reports assume a human is sitting in front of them. Our Grammarly vs ProWritingAid comparison concluded that ProWritingAid is arguably the better tool for long-form creative writing. The catch is that all of that depth lives inside ProWritingAid's own interface, and there's no way to lift it into yours.
The migration is smaller than you think
If you came here hoping to pipe ProWritingAid into your app, the good news is the API category is designed for exactly that. A typical proofreading API call is a single POST with your text; the response is a list of edits — each with a start offset, end offset, replacement text, and an explanation — that you render however you want. Underlines, hover cards, accept/reject buttons: your UI, your brand.
The grammar checker API comparison walks through all seven options developers actually evaluate, with public benchmark data and the methodology to reproduce it. What you'll actually pay models the billing math. And if you want to see the edit format before committing to anything, AmberPen's Starter plan is €5/month with 500K characters included — a free test key returns real corrections in about two minutes.