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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. Grammarly publishes a starting price ($12); Compose AI does not. Both have a free tier.

Compose AIFree Chrome extension that autocompletes sentences and email replies as you type across the webGrammarlyGrammar, tone and rewriting help inside every app

Side by side

FactCompose AIGrammarly
CategoryAI Writing AssistantsGrammar & Proofreading
Pricing modelFreemiumFreemium
Starts at—$12 month
Public APINoNo
PlatformsChrome ExtWeb, Chrome Ext, Windows, macOS, iOS, Android
CompanyCompose AI, Inc.Superhuman
Launched20212009
Last verifiedSep 6, 2026Sep 6, 2026

What our research says

Compose AI

A low-friction way to speed up routine email and doc writing, since the free tier installs in a minute and completes sentences anywhere in Chrome. The catch is stagnation risk: the site's own copyright is frozen at 2024 and browser-native AI features increasingly do the same job for nothing.

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

Cons

  • Chrome-only, with no API or desktop apps
  • Official pricing was unreadable in this check, an odd sign for a paid product
  • Site freshness signals suggest limited ongoing development

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

More comparisons

All Compose AI alternatives →Browse all AI Writing Assistants →