AI Grammatic vs ChatGPT for rewriting your messages

Many people who write at work in a second language already have a routine. Write the message, copy it, paste it into ChatGPT with "make this sound natural," copy the answer, paste it back, then fix whatever came out wrong. It works. It's also six or seven steps for a two-line Slack reply.

AI Grammatic turns that routine into one shortcut. This page compares the two honestly, including the cases where ChatGPT is the better tool.

The short answer

For rewriting what you've already written (emails, Slack messages, tickets, comments, pull request descriptions), AI Grammatic is faster and more predictable: select, press ⌘⌥E, and the text is replaced in place. For drafting from a blank page, working on long documents or asking why a sentence is wrong, ChatGPT is the better fit. Plenty of people use both.

What rewriting with ChatGPT looks like

1. Select your text and copy it.
2. Switch to ChatGPT, in a browser tab or the Mac app.
3. Type a prompt, such as "Fix the grammar and make it sound natural, keep it short."
4. Paste your text and wait for the answer.
5. Copy the rewritten part, skipping the "Here's a more polished version" line.
6. Switch back and paste over the original.
7. Check that names, links and formatting survived.

The ChatGPT Mac app shortens step 2: by default ⌥Space opens a small chat bar over whatever you're doing. OpenAI has also added ways for its Mac app to read from and work in some other apps, and in July 2026 it replaced the Mac app with a new desktop app that combines chat with its Work and Codex agents. The previous app is still available as ChatGPT Classic. Those features are built for bigger jobs. For a quick message, most people still copy and paste.

What it looks like with AI Grammatic

1. Select the text in Slack, Mail, Notion, your browser or any other app.
2. Press ⌘⌥E, or ⇧⌘⌥E for a formal version.

About a second later the text is replaced in place. It's a normal paste, so ⌘Z brings back what you wrote. There's no prompt to write, because the instructions are built in. You can see it for yourself in the live demo.

A prompt you never have to write

The quality of a ChatGPT rewrite depends on what you ask for, and a busy person types a shorter prompt every time. Every AI Grammatic rewrite follows the same rules:

• Fixes grammar, spelling, punctuation, capitalization, articles and prepositions.
• Replaces literal translations, unnatural word choices and awkward word order with natural phrasing.
• Keeps your meaning, names, numbers, links, @mentions, emoji, formatting and line breaks.
• Stays about the same length and doesn't add greetings or sign-offs you didn't write.
• Never uses em dashes and avoids stock AI phrases, so your message doesn't read like a chatbot wrote it.

You can add your own rules on top. Pick a rewrite style (neutral, professional, casual or concise), turn on the No dashes option, or write custom instructions of up to 500 characters on any plan, such as "I work in fintech, keep product names in English."

Same models, fewer steps

AI Grammatic isn't a different kind of AI. On Premium ($69 a year, €59 in the EU) we run the AI for you, with up to 50,000 words a day, and you pick the model: OpenAI, Claude, Gemini or DeepSeek. On Pro ($29 a year) you connect your own API key from OpenAI, Anthropic, Google or DeepSeek and rewrite as much as you like. If you like how OpenAI's models write, you can keep using them. What changes is everything around the model. The Free plan gives you 10 rewrites a day with no account and no API key. See pricing for the details.

Translation without a prompt

ChatGPT translates well when you ask. AI Grammatic does it without asking: if the text you select is in another language, it's rewritten into the target language the way a native speaker would say it, not word for word. Each language gets its own shortcut (your default plus up to five more), so going from Russian notes to English, or from English to German, is just a different key.

Your text and your data

When you rewrite in ChatGPT, your text becomes a conversation in your chat history. On personal plans (Free, Plus and Pro), OpenAI says conversations can be used to train its models by default. You can turn that off under Settings, Data controls, "Improve the model for everyone." OpenAI says its business plans and its API don't train on your inputs by default.

AI Grammatic has no chat history. On Free and Premium your text passes through our server to the AI provider and is discarded after the rewrite. We keep only daily usage counts. On Pro your text goes straight from your Mac to your own AI provider account, so with an OpenAI key, OpenAI's API terms apply rather than ChatGPT's. More in how we handle your text.

Where AI Grammatic fits

Think of it as the tool for the small messages you send all day, not the one big document. It's a menu bar app for macOS 14 or later, a direct download signed and notarized by Apple. It isn't on the App Store because it needs macOS Accessibility access to replace text in other apps. If English isn't your first language, our page for non-native English speakers shows more examples. And if you're weighing the tools already on your Mac, read AI Grammatic vs Apple Writing Tools.