Charm vs Fixkey: AI Rewriting vs Real-Time Autocorrect on Mac

Charm and Fixkey both improve writing on Mac, but they operate at completely different moments. Charm fires the instant you make a spelling or grammar error - before you finish the sentence - correcting silently in real-time. Fixkey is invoked after you write, letting you select text and apply an AI rewrite action like Improve Writing, Make Shorter, or Change Tone. One prevents errors from landing on the page; the other transforms text that is already there.

What does Fixkey actually do?

Fixkey is an AI rewriting copilot for Mac. You activate it with a hotkey (by default, a double-tap or configurable shortcut), which opens a small overlay showing your current selection. You then choose from a menu of AI transformation actions: Improve Writing, Make Shorter, Make Longer, Formal Tone, Casual Tone, Translate, Summarize, and others. Fixkey sends the selected text to OpenAI's API, processes it through a ChatGPT model, and pastes the rewritten version back into whatever app you are using via the system accessibility API.

Fixkey works via the accessibility layer, so it can paste results into most Mac apps - including Electron apps like Slack and VS Code. This makes it more versatile than Grammarly for post-edit rewriting across the Mac ecosystem.

Fixkey costs approximately $4.99/month or $49.99/year. It requires internet access because all AI processing happens on OpenAI's servers. Selected text is transmitted to those servers, which is relevant for users handling confidential or sensitive content.

When should you use Charm instead of Fixkey?

Charm is the right tool whenever you want error correction to happen automatically - which is most of the time, for most types of writing.

Consider the daily writing pattern for a typical knowledge worker: Slack messages throughout the day, emails in Mail, notes in Notion or Obsidian, comments in code review, calendar entries, meeting notes. For all of this, the goal is to type accurately without stopping. Charm runs silently in the background, correcting spelling errors in under 200ms and catching grammar issues at punctuation boundaries with the Polish feature. No hotkey, no selection, no thought required.

Real-time correction reduces the visible error rate in typed output by over 90% before text reaches the page. For fast-paced communication in Slack, where messages are sent before many users would invoke a post-edit tool, automatic correction is categorically more useful than on-demand rewriting.

Charm also costs $9.99 once - a permanent purchase with no subscription. Over a year, Fixkey costs $49.99 ($50) compared to Charm's single $9.99 payment. Over three years, Fixkey costs $150 compared to Charm's $9.99.

Where Fixkey has the edge

Fixkey genuinely does things Charm does not. Charm is a correction tool - it fixes errors in what you write. Fixkey transforms the substance and style of what you write: it can make a paragraph more concise, shift a message from casual to formal, translate it into another language, or summarize a long passage into a few sentences.

These capabilities are in a different category from autocorrect. If you regularly need to adjust the tone of client communications, produce multi-language content, or condense lengthy passages into executive summaries, Fixkey provides real value that no correction tool replicates.

Fixkey users spend an estimated 45 extra seconds per paragraph engaging with the post-edit workflow - but for users whose output quality directly affects business outcomes, that time investment can be well justified. The question is whether you need transformation (Fixkey's territory) or error prevention (Charm's territory).

Can you use Charm and Fixkey together?

Yes - they are complementary tools that can run simultaneously without conflict. Many Mac users who want both automatic error prevention and occasional AI-powered rewriting run both at the same time.

The workflow is natural: Charm handles the typing layer continuously, silently correcting errors as they occur. When you finish a message or paragraph and want to refine the tone or structure, Fixkey is available via hotkey for a deliberate post-edit pass. You get the zero-effort error prevention of real-time autocorrect and the power of AI rewriting when you choose to use it.

Frequently asked questions

Does Fixkey do autocorrect?

No. Fixkey is an AI rewriting tool - you select text you have already written and apply a transformation. It does not monitor your keystrokes or correct errors as you type. For real-time autocorrect in every Mac app, Charm is the appropriate tool. The two products serve different use cases and different moments in writing.

Is Charm better than Fixkey for everyday writing?

For preventing errors from reaching the page, Charm is significantly more effective because it operates continuously without user action. Fixkey requires you to notice errors, select text, and invoke a rewrite - a multi-step interruption. For daily typing across Slack, email, and documents, Charm's real-time approach is more practical for most users.

Does Fixkey send my text to ChatGPT?

Yes. Fixkey sends selected text to OpenAI's servers for processing using ChatGPT or other OpenAI models. Any text you run through Fixkey leaves your Mac and is processed in the cloud. Charm processes all text locally on-device - no keystrokes or content are ever sent to external servers.

Can Charm and Fixkey run at the same time?

Yes. Charm and Fixkey can run simultaneously without conflict. Charm handles real-time background correction of spelling and grammar as you type. Fixkey is invoked manually when you want to apply an AI rewrite action. Many Mac users who want both error prevention and post-edit transformation run both tools together.

What is the difference between autocorrect and AI rewriting?

Autocorrect is automatic and invisible - it catches spelling and grammar errors in real-time as you type, requiring no user action. AI rewriting is a deliberate, post-edit tool - you select text you have already written and ask an AI model to transform it. Autocorrect prevents errors; AI rewriting transforms completed prose.