TextGears

TextGears has a free plan that covers 500 text checking requests a month, plus 200k characters of translation or rephrasing, with up to 4k characters per request.

TextGears is a grammar and spelling check platform with an API, and it supports multiple languages.

It also handles paraphrasing and translation, so developers can add proofreading features to an app or editor without building their own checker.

Paid plans scale by request volume.

Silver costs $23.96 a month for 50k text checking requests.

Gold costs $79.96 a month for 500k requests and raises the per-request text limit to 16k characters.

Platinum is for millions of requests, with limits set individually, and you contact the team for it.

The free tier is enough to test the API on a small project.

Heavier use means moving up a plan, since the request cap is the main constraint.