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Grammarly grammarly.com

Can AI replace Grammarly?

You can build grammar checks and rewrites, but Grammarly's moat is cross-app extensions, inline UX, enterprise controls, writing telemetry, and long-running language quality.

Verdict: Half-bot · AI gets you partway; the hard part stays hardBuild time: multi-day
Half-bot

01What it costs

$30/moPro, monthly
$360per year at that price

Checked Aug 12, 2026 · source: grammarly.com.

PlanMonthlyBilled yearlyWhat you get
FreeFreeFree100 generative-AI prompts/month.
Pro$30$12/mo2,000 AI prompts/member/month; up to 149 seats; 1 style guide; 1 brand tone; 2 groups.
Enterprise——Unlimited prompts, members, style guides, brand tones, and groups.

Hidden costs: Additional Pro seats are prorated. A 7-day trial is available only for eligible accounts.

02Could AI build it for you?

The core job: Run text through LanguageTool plus an LLM rewrite/tone checker, expose a browser extension or local editor.

What a working version needs:

  • grammar engine/API
  • LLM API
  • browser extension
  • optional desktop accessibility layer
  • user dictionary

An important 'kinda': grammar checking is open-source, cross-app UX is the hard product.

03What you'd give up

  • inline suggestions everywhere
  • document/email integrations
  • tone/brand controls
  • enterprise admin
  • polished false-positive handling

They pay because suggestions appear inside the apps where writing actually happens.

04Free and cheaper alternatives

Apple Writing Toolsfree

Proofread, rewrite, shorten, or change tone almost anywhere, assuming your Apple hardware made the guest list.

Versus paying: It is restricted to supported Apple hardware and offers fewer continuous cross-app style, brand and writing analytics controls than Grammarly.

support.apple.com →
Harperopen-source

A fast English grammar checker that stays on your device and mostly keeps its opinions to itself.

writewithharper.com →
Writing Toolsopen-source

Select text anywhere, hit a hotkey, and fix, rewrite, summarize, or obey a custom instruction without opening another tab.

Versus paying: It is a manual select-text-and-hotkey workflow rather than Grammarly's continuous inline underlines and suggestions across supported apps.

github.com →
WritingToolopen-source

A LibreOffice extension with long-document checks, style statistics, profiles, and local AI; installing Java is the cover charge.

Versus paying: It is centered on LibreOffice rather than working continuously across browsers, email and arbitrary desktop apps like Grammarly.

writingtool.org →

05The build prompt

Paste this into an AI coding tool (such as Claude, ChatGPT, Lovable or Replit) to build your own version.

prompt.txt
Build me a personal writing checker to replace Grammarly. Requirements:

- Grammar engine: LanguageTool running locally via its official Docker image;
  grammar checks never leave my machine.
- A local web page (Node + Express, binds to localhost): paste text, see
  LanguageTool issues underlined with hover explanations, click a suggestion
  to apply it.
- An LLM rewrite pane (key in .env) with three buttons: tighten, friendlier,
  formal. Show a diff against my original before I accept anything.
- A personal dictionary file (dictionary.txt) of names and jargon to never
  flag, passed to LanguageTool on every check.
- CLI mode: `check <file.md>` prints issues with line numbers, exits nonzero
  if any, so it can run as a git pre-commit hook on docs.
- Everything local except the optional LLM call; no accounts, no telemetry.
- Out of scope: a browser extension and inline suggestions inside Gmail,
  Docs, or Slack. This is a destination I paste into, that is the honest
  trade against Grammarly.
- README: Docker setup for LanguageTool, the roughly 1 GB of RAM it wants,
  and where the LLM key goes.

06Open-source starting points

  • LanguageTool: Open-source grammar and style checker and the primary Grammarly-like prior art.
Sponsor slot · openFeatured alternative to Grammarly. A labeled card for one relevant tool.
Book this spot →

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App prices, verdicts, alternatives and build prompts are adapted from Can I Vibecode It? (MIT License, © 2026 Rob Hallam). Each price shows the date it was checked and its source. Prices change; confirm on the vendor's site before you decide.