If you're searching for an open-source Grammarly alternative, the usual asks are: grammar checking that works where you type, no subscription, and your drafts not flowing through someone else's service. OpenCues covers that ground: shipped grammar correction, with an opt-in clarity concern, rewriting as you type, running on a model you choose, including one on your own machine.
How the grammar experience compares
| Grammarly | OpenCues | |
|---|---|---|
| Model | Grammarly's own service | Your choice: Cerebras, Groq, OpenAI, Anthropic, Gemini, OpenRouter, or local Ollama |
| Interaction | Proposes; you accept each suggestion | Applies the fix dimmed in place; ignoring accepts, cycling reverts |
| Configuration | Settings UI | One markdown file per concern; readable, editable, per-project disableable |
| Cost | Freemium subscription | Free and open source; you pay only your provider (free tiers exist) |
| Data path | Grammarly's servers | Directly to your configured provider on your key; fully local with Ollama |
The design difference that matters daily
Grammarly's model is suggest-and-approve: nothing lands without an accept, individually or in batches. OpenCues inverts the default for the common case: clear grammar fixes land dimmed in your text, doing nothing accepts them, and any fix reverts individually with two keys (Ctrl+Alt+←/→ to reach it, Ctrl+Alt+↓ to cycle back). One concern at a time means grammar and clarity are separate concerns you can enable or disable per project, not sliders on a monolithic engine. And the same runtime gives you things Grammarly's correction engine doesn't attempt: translate to japanese _, lookups, live values, word alternatives.
The honest gaps
Grammarly is a mature consumer product; OpenCues is pre-1.0 open source. Grammarly runs OS-wide including native apps and Word; OpenCues runs in its supported hosts, and notably not in Google Docs. Grammarly ships tone detectors, plagiarism checking, and team style guides; OpenCues has no equivalent of those. If you want zero-setup polish everywhere, Grammarly remains the safer pick; if you want inline writing assistance you control end to end, on your own key, that's what OpenCues is for.
Getting the grammar setup
Install once, set a provider key (or point at Ollama for fully local), and grammar correction ships enabled, riding along whenever the inline agent runs. The grammar guide covers the three modes: continuous correction, one-shot fix the grammar _, and an armed agentically correct spelling _ task.
Related: OpenCues vs Grammarly · Self-hosted setup · GitHub repo