Compose AI vs Grammarly

Two fact sheets from our own research, side by side — pricing, platforms, API access and status re-checked by us rather than quoted from the vendors.

The short answer

Cheaper paid plan: Compose AI — $9.99/mo vs $12/mo for Grammarly
Free plan: Both have one
Best fit: Compose AI: Heavy email writers who churn out routine replies in Gmail · Grammarly: Anyone writing in a browser, Word or email who wants corrections in place
Platforms: Compose AI: Chrome extension · Grammarly: Web, Chrome extension, Windows, macOS, iOS, Android
Trust score: About even — Compose AI 96, Grammarly 94

From our own records as of each tool's last check. Anything we have not confirmed is left out rather than guessed. How we verify

Compose AIFree Chrome extension that autocompletes sentences and email replies as you type across the web

GrammarlyGrammar, tone and rewriting help inside every app

Side by side

Fact	Compose AI	Grammarly
Category	AI Writing Assistants	Grammar & Proofreading
Pricing model	Freemium	Freemium
Starts at	$9.99/mo	$12/mo
Trust score	96 / 100	94 / 100
Platforms	Chrome extension	Web, Chrome extension, Windows, macOS, iOS, Android
Company	Compose AI, Inc.	Superhuman
Launched	2021	2009
Last verified	Oct 16, 2026	Oct 16, 2026

What our research says

Compose AI

A low-friction way to speed up routine email and doc writing: the free tier installs in a minute and completes sentences anywhere in Chrome. The extension is still being updated, but its free caps are small and browser-native AI features now cover much of the same ground at no cost, so the paid tiers have to earn their place.

Pros

Basic extension is free with no time limit
Autocomplete works across most web text fields, not one app
Learns personal writing style for suggestions
Annual billing cuts the Premium price by a third

Cons

Chrome-only, with no public API or desktop apps found
Free plan caps AI writing at 1,500 words a month
Marketing site copy and copyright are still dated 2024, which makes the product look less maintained than its store listing suggests

Grammarly

Still the default for catching mistakes inside other people's software, but the free tier has quietly become an AI-prompt meter and the honest price is $30 unless you commit to a full year.

Pros

Runs inside the apps people already write in rather than as a separate editor
Free tier still covers spelling, grammar and tone detection with no time limit
Pro folds in plagiarism and AI-text detection that rivals charge for separately

Cons

The $12 headline is the annual rate; paying monthly costs $30
Free AI allowance is 100 prompts a month and depletes quickly
No public API, so it cannot be embedded in another product
Enterprise pricing is not published anywhere on the site

Which one fits

Choose Compose AI if you need

Heavy email writers who churn out routine replies in Gmail
Non-native English speakers who want inline phrasing help
Anyone testing writing autocomplete without paying

Choose Grammarly if you need

Anyone writing in a browser, Word or email who wants corrections in place
Teams enforcing a house style guide across people who are not writers
Non-native English speakers who want fluency rewrites, not just error flags