Works offline
- Refine
- Yes, after downloading a local model
- Harper
- Yes
Refine vs Harper
Local AI or open-source rules?
Refine and Harper both keep grammar checks on your device. They take different approaches to helping you write.
v1.34
macOS 14+
Full-featured 7-day free trial
Quick comparison
| Feature | Refine with local model | Harper |
|---|---|---|
| Works offline | Yes, after downloading a local model | Yes |
| Checking approach | Contextual local AI | Deterministic grammar rules |
| Language coverage | 50+ languages and regional variants | English with five dialect settings |
| Price | $38 one-time lifetime license | Free and open source |
Checking approach
- Refine
- Contextual local AI
- Harper
- Deterministic grammar rules
Language coverage
- Refine
- 50+ languages and regional variants
- Harper
- English with five dialect settings
Price
- Refine
- $38 one-time lifetime license
- Harper
- Free and open source
Refine vs Harper feature comparison
Both products can check writing locally. The main difference is whether you want contextual AI assistance or a deterministic rule-based checker.
Where checks run
Refine
On your Mac with a downloaded AI model.
Harper
On your device with its local grammar engine.
Private local checks
Refine
Checked text is not uploaded to Refine servers.
Harper
Harper says its grammar engine uses no telemetry and sends no writing to a server.
Grammar and spelling
Refine
Context-aware grammar and spelling corrections.
Harper
Grammar, spelling, punctuation, and style suggestions from deterministic rules.
Broader writing tools
Refine
Fluency improvements, explanations, translation, and custom prompts.
Harper
Focused on lint messages and suggestions rather than generative rewriting.
Customization
Refine
Custom prompts, instructions, language choices, and model settings.
Harper
Toggle rules, add personal dictionary terms, and extend rules with Weirpacks.
Where you can use it
Refine
Across most Mac apps on macOS 14 or later.
Harper
Browser and editor integrations, plus a beta desktop app for macOS 14 or later. These integrations are not system-wide.
Price and license
Refine
$38 once for one Mac, or $68 once for 3 Macs.
Harper
Free and open source.
Limits of fixed rule coverage
Where deterministic rules can miss context
A deterministic checker can leave an error unchanged when no matching rule fires. The examples below show the outputs observed in a same-input local check.
For each example, we used the same American-English input with both tools, ran the versions shown locally, and compared their outputs with the expected minimal correction. These examples illustrate particular rules and are not an overall accuracy ranking.
Refine v1.34 with Gemma 4 E2B and Harper CLI 2.6.0, both using American English.
What the local check showed
With the same input, the language-model output matched the expected minimal correction. The rule-based checker returned no finding.
Adjective before a noun
The noun “decision” needs the adjective “quick” here, not the adverb “quickly.”
Text to check
The team made a quickly decision before noon.
Expected change
Language model: Caught
Changed “quickly” to “quick.”
Rule-based checker: Missed
No finding; the error stayed unchanged.
Object pronoun after a verb
The pronoun is the direct object of “thanked,” so it needs the object form “her,” not “she.”
Text to check
The courier thanked she for the detailed note.
Expected change
Language model: Caught
Changed “she” to “her.”
Rule-based checker: Missed
No finding; the error stayed unchanged.
Plural subject–verb agreement
The plural subject “doors” takes “have,” not the singular form “has.”
Text to check
The warehouse doors has closed for the night.
Expected change
Language model: Caught
Changed “has” to “have.”
Rule-based checker: Missed
No finding; the error stayed unchanged.
Base verb after a modal
After the modal “must,” English uses the base verb “check,” not “checks.”
Text to check
The driver must checks the mirrors before leaving.
Expected change
Language model: Caught
Changed “checks” to “check.”
Rule-based checker: Missed
No finding; the error stayed unchanged.
Which writing assistant should you choose?
Choose Refine for contextual writing help
Refine is a better fit when you want local AI to understand sentence context and help beyond rule-based grammar.
- You want fluency improvements, explanations, translation, or custom prompts.
- You write in languages beyond English.
- You want one writing assistant across most Mac apps.
Choose Harper for a free, rule-based checker
Harper is a better fit when you want an open-source checker with predictable, configurable rules.
- You prefer deterministic rules over a language model.
- You want a Harper-supported browser or editor integration and do not need system-wide checking.
- You want a free checker you can inspect and extend.
Refine vs Harper FAQ
Do Refine and Harper work offline?
Yes. Refine checks text locally after you download an AI model. Harper's grammar engine also runs locally.
Do Refine and Harper upload my writing?
Refine does not upload checked text to Refine servers. Harper says its local grammar engine has no telemetry and sends no writing to a server.
When is Harper a better fit?
Choose Harper when you want a free, open-source, rule-based checker with supported browser and editor integrations, rather than system-wide checking across Mac apps.
When is Refine a better fit?
Choose Refine when you want contextual local AI, support for more than 50 languages and variants, fluency help, explanations, translation, and custom prompts across Mac apps.
Source notes
Harper product details were reviewed July 30, 2026. Product features can change after review.
All comparisons
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v1.34
macOS 14+
Full-featured 7-day free trial