[verdict][generated prompt][source: grammarly.com]
Can I vibecode Grammarly?
// buildable in a weekend, but real gaps stay open
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.
confidence: medium
what it is: Grammar, clarity, tone, and AI writing assistant across apps
Buildability index · an editorial game
- Price 30 $/month weight: plus 3
- Time multi-day weight: plus 1
- Category ai writing no weight
- Moat integrations · proprietary models · execution quality weight: minus 4
- Confidence medium weight: zero
- What you lose 5 items weight: minus 2
- Site grammarly.com (si apre in una nuova scheda) no weight
The moat outweighs the price: rebuilding this is a project, not an evening.
Gioco editoriale: il verdetto dice se un agente può, l’indice se conviene.
What you build
Run text through LanguageTool plus an LLM rewrite/tone checker, expose a browser extension or local editor.
what you need
- 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.
The prompt
A weekend with a coding agent. The gaps that stay are right below, under “what you lose”.
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.Prompt generated from the data on this page, not reviewed by hand yet. In English on purpose — it is the language coding agents work best in.
What you lose
- inline suggestions everywhere
- document/email integrations
- tone/brand controls
- enterprise admin
- polished false-positive handling
Why people still pay
They pay because suggestions appear inside the apps where writing actually happens.
moat: Integrations Proprietary models Execution quality what a moat is
cross-app integration/model quality
Free alternatives
Not in the mood to build it? These already exist, they are free or open source, and we checked them one by one.
Apple Writing Tools free (si apre in una nuova scheda) — — one-click deploy Proofread, rewrite, shorten, or change tone almost anywhere, assuming your Apple hardware made the guest list. Harper open source (si apre in una nuova scheda) 14.2k ★ Aug 2026 one-click deploy A fast English grammar checker that stays on your device and mostly keeps its opinions to itself. Writing Tools open source (si apre in una nuova scheda) 2.4k ★ May 2026 one-click deploy Select text anywhere, hit a hotkey, and fix, rewrite, summarize, or obey a custom instruction without opening another tab. WritingTool open source (si apre in una nuova scheda) 65 ★ Jul 2026 one-click deploy A LibreOffice extension with long-document checks, style statistics, profiles, and local AI; installing Java is the cover charge. Rejected (1) — and why
- LanguageTool Free (si apre in una nuova scheda) — The engine is open source, but the browser extension went Premium-only in 2026; the free web checker no longer replaces across-app use.
Who has already built it
Starting from here is still vibecoding: the prompt is for when you want it exactly your way.
- LanguageTool (opens in a new tab) — Open-source grammar and style checker and the primary Grammarly-like prior art. (alive)
Do you agree?
The vote balance
Ancora nessun voto: il tuo è il primo.
Nessun voto ancora — il primo pesa.
