What AI model does it use?

What AI model does Grammarly use?

This is one of the apps that doesn't tell you. Grammarly's help pages talk about "generative AI" throughout and never name a model, and there's nowhere in the app to choose one. So the answer here is what Grammarly and its parent company have put on the record, and there's a fair amount of it.

What Grammarly itself says

The plainest statement is in a Grammarly blog post from April 14, 2025, about an AI management certification: "Our generative AI is powered by trusted partners like Microsoft Azure OpenAI and OpenAI, but customer data is never shared for model training." Azure OpenAI is Microsoft's cloud service that sells OpenAI's models, so both names point at OpenAI's models, reached two different ways.

Grammarly also builds some models of its own. Its responsible AI page mentions a "proprietary machine learning content-filtering solution", which is a filter around the generative models (it screens what the models see and say, rather than writing anything).

The provider list names Anthropic too

Grammarly is now part of Superhuman, and the two share one subprocessor list, the legal page that names every outside company handling customer data. It says it covers the "Superhuman Platform (including products offered as "Grammarly", "Coda", "Superhuman Go", and "Superhuman Mail")."

Three companies on it are labeled "Generative AI provider": Anthropic, Azure and OpenAI. Anthropic makes the Claude models. Grammarly's own trust copy still names only the two OpenAI routes, so the list is the only first-party place I found Anthropic connected to Grammarly, and it doesn't say which product or feature uses it.

One place a model is named: GPT-5 for agents

The only specific model version I found is on the developer side. Superhuman's developer blog says that "As of February 12, 2026, the default LLM model used by Superhuman Go agents has been updated from OpenAI's GPT-4 to GPT-5." Superhuman Go is the agent platform, where developers build add-ons, and they can pin the older model per skill if they want.

That's a default for agents built on the platform. It doesn't say the grammar suggestions or rewrite features in the Grammarly editor run on GPT-5, and I didn't find anything that does.

Why the answer stays vague

With three providers on the list and no picker, Grammarly can move a feature from one model to another without anything visible changing for you. The subprocessor page says it will post updates there when providers change, which is why it's the page this answer watches each month.