Grammarly is a polished, closed writing assistant. OpenCues covers the same ground (grammar correction ships enabled, with clarity a toggle away) but with a different philosophy: your model, your config files, your surfaces, and an open standard underneath.
The key differences
- Bring your own model. Grammarly runs on its own service. OpenCues runs on whichever provider you configure, including local models via Ollama, so your drafts go only where you decide.
- Edits land, reverts are one gesture. Grammarly proposes; you accept suggestions, singly or in batches. OpenCues applies the fix dimmed in place; doing nothing accepts it, and cycling reverts it. Fewer decisions for the common case.
- One concern at a time. Grammar and clarity ship in the box as separate concerns you can enable or disable per project. Not a monolithic style engine.
- More than grammar. The same runtime gives you blanks (
translate to japanese _,volume _) and word-alternative cues, which Grammarly's correction engine does not attempt. - Open. Free, open source, and specified in an open standard; Grammarly is a proprietary subscription.
If you want a zero-setup consumer product, Grammarly is mature. If you want inline writing assistance you control end to end, running on your own key in your terminal, your browser, and your AI tools, that is OpenCues.
Newer axes worth knowing: OpenCues routes each feature to its own model (grammar on a fast cheap model, rewrites on your Claude plan), keeps identity values off providers by tokenising them before any cloud call, and ships project-level config your team commits to a repo, where Grammarly offers business style guides. Grammarly's mobile keyboards remain a real advantage: OpenCues has no mobile host today.
Where Grammarly struggles
Everything runs through Grammarly's cloud on Grammarly's models: no key of your own, no local mode, and your text is always in transit to score it. The overlay injection that gives it reach also makes it a guest in every editor it decorates, and complex web editors are where extensions like it historically misbehave. Correction is its center of gravity; generation lives behind a widget and a prompt box.
By the numbers
Grammarly's underlines are the only passive layer in the field that rivals cues: two gestures to apply a suggestion, same as OpenCues. The explicit paths cost more: four steps to generate or rewrite against one, with a click of Accept as end-lag, and it puts three to four surfaces on screen (widget, underlines, cards, panel) where OpenCues adds none. The matching passive costs cover different ranges too: underlines flag correctness, while cues cycle alternatives and tips, with the whole blank grammar underneath. Counts and sequences in the full comparison.
Related: Fix grammar as you type · Open-source Grammarly alternative · OpenCues vs Apple Writing Tools · GitHub repo