Charm
on-device spelling, grammar, and prediction for macOS
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What is Charm?
Charm is a native macOS menu bar app that serves as a personal writing partner, correcting spelling, fixing grammar, and predicting your next word in every app on your Mac. It features three core tools: Spells for real-time spelling correction with a cyan glow overlay (catching errors like
Charm pricing
Pricing model: Freemium
$9.99 one-time purchase with no subscription. No renewal, no account required. Single license works on up to 3 Macs and includes all updates. Optional OpenAI API key integration costs pennies per day (usually under $1/month) billed directly by OpenAI at their published API rates with no markup from Charm. You can set a monthly spending limit in your OpenAI account dashboard.
Charm pros
- One-time $9.99 payment with no subscription or renewal
- Works system-wide across every Mac app simultaneously
- 100% on-device processing - text never leaves your Mac
- No account required - complete privacy by default
- Spells corrects spelling in under 200ms as you type
- Polish catches grammar errors at sentence boundaries
- Oracle predicts next word with context-aware suggestions
- License works on up to 3 Macs with included updates
- Per-app settings to disable features for specific apps like VS Code
- Manual mode (Cmd+Opt+V) works in Electron apps like Slack
- Choose between Gemma 2 2B or Qwen 2.5 3B model
- Optional OpenAI integration catches 35% more complex grammar issues
- Model auto-unloads after 5 minutes idle to bound RAM usage
- OpenAI key stored securely in macOS Keychain encryption
- Built in Swift/SwiftUI as a native Mac app
- Falls back to on-device mode automatically if OpenAI connection fails
Charm cons
- Requires Accessibility and Input Monitoring permissions
- Does not work in password fields due to macOS restrictions
- Oracle is off by default and must be enabled manually
- No deep manuscript analysis like ProWritingAid's 25+ reports
- Only works on macOS - no Windows or Linux support
- No cloud option exists for users who prefer server processing
- OpenAI integration requires separate OpenAI account with billing
- Model downloads from HuggingFace on first use requiring internet
Frequently asked questions about Charm
Does Charm require an OpenAI API key?
No. An OpenAI API key is completely optional. Charm's Polish feature works on-device by default - no key required, no internet needed, and no text ever leaves your Mac. The OpenAI integration is available for users who want more powerful grammar correction and are comfortable with OpenAI's privacy policy.
Is my text sent to OpenAI when I use Charm?
Only if you have configured an OpenAI API key and enabled the integration. In the default on-device mode, no text is sent anywhere - all processing happens locally on your Mac. When the OpenAI integration is active, the text you are correcting is sent to OpenAI's API using your key and subject to OpenAI's terms of service.
How much does OpenAI API cost for Charm grammar correction?
Grammar correction uses a very small number of tokens per correction. For typical daily use, the cost is pennies per day - usually under $1 per month. You pay OpenAI directly at their published API rates; Charm does not add any markup. You can also set a monthly spending limit in your OpenAI account dashboard.
Is my OpenAI API key stored securely in Charm?
Yes. Charm stores your OpenAI API key in the macOS Keychain - the same encrypted system used by Safari for saved passwords and Apple Pay for card data. The key is never written to Charm's preferences file or any plain-text storage. Removing the key from Charm deletes it from the Keychain.
How do I enable Oracle in Charm?
Click the Charm icon in your Mac menu bar and toggle the Oracle switch to the on position. Oracle is off by default, so you need to enable it once after installing Charm. From that point it works automatically across every Mac app.
How do I accept a word prediction from Oracle?
Press the Tab key when you see a grey word suggestion appear after your cursor. The predicted word is inserted immediately and your cursor moves to the end of it, ready for you to continue typing.
How is Oracle different from regular autocomplete?
Standard autocomplete only suggests ways to finish the word you are currently typing. Oracle predicts the next word entirely - it reads the full context of what you have written and suggests what comes next, similar to predictive text on a smartphone keyboard but available across every Mac app.
Does Oracle work in every Mac app?
Yes. Oracle works in any app that accepts text input on macOS - Mail, Slack, Notes, Pages, Chrome, Safari, and thousands more. If you find Oracle disruptive in a specific app such as a code editor, you can disable Charm for that app individually from the menu bar.
Does Oracle send my typing to the internet?
No. Oracle runs entirely on your Mac using on-device machine learning models. Your keystrokes and the text you type are never sent to a server. No internet connection is required for word prediction to work.
Can I disable Charm for specific apps?
Yes. Charm's per-app settings let you disable specific features for individual apps. For example, you can disable Polish (grammar) for VS Code while keeping Spells (spelling) active. Click the Charm icon while the app is in focus and select 'Disable for [App Name]' to turn off features for that specific application.