Real-Time Grammar Correction on Mac: The Complete Guide

macOS does not have real-time grammar correction. It has spell check - the red squiggle under misspelled words - but no engine that detects and fixes grammar errors as you type. The tools most people reach for, like Grammarly, are post-edit tools: they surface suggestions after you have finished writing rather than correcting grammar while typing. Charm's Polish is the only tool on Mac that fixes grammar as you type, in every app, automatically.

What does real-time grammar correction actually mean?

The term gets used loosely, so it is worth being precise. Real-time grammar correction means that grammar errors are detected and fixed automatically while you are still in the act of writing - not after you have finished a sentence, not in a review sidebar you have to consult, but in-place and invisibly, as part of your natural typing flow.

The key distinction is between correction that happens while typing and correction that happens after writing. When a tool corrects grammar while typing, the error never reaches its destination. When a tool corrects after writing, the error exists in your draft until you catch it - and if you forget to review, it goes out uncorrected.

For spell check, real-time has been the standard for decades. You type "teh", macOS corrects it to "the" before you have even finished the word. That same immediate, automatic behaviour has not existed for grammar - until tools like Charm's Polish made it possible.

Research from the Writing Studies journal found that writers who receive real-time correction fix 3x more errors than writers who receive post-edit suggestions. The reason is simple: errors corrected at the moment of creation are harder to miss than errors surfaced in a review tool that requires a separate action.

Why doesn't Mac have native real-time grammar correction?

macOS includes a grammar-checking framework called NSSpellChecker, which has existed since the early days of Mac OS X. It covers spelling reliably and offers basic grammar checking to apps that opt in. But the native grammar checker has two significant limitations that prevent it from functioning as a real-time system.

First, NSSpellChecker operates reactively rather than continuously. It flags errors with a green underline and waits for the user to right-click and select a correction. It does not apply corrections automatically. The user must take an action for each flagged error.

Second, native grammar checking only works in apps built with Apple's standard text frameworks (AppKit text views). Apps built with custom text engines - including most Electron-based tools, cross-platform apps, and many productivity tools - do not receive native spelling or grammar checking at all. This leaves large portions of daily writing completely unprotected.

macOS 15 Sequoia introduced Apple Intelligence Proofread, which uses an on-device transformer model to suggest grammar corrections. It is more capable than the original NSSpellChecker grammar rules, but it still requires manual invocation: you select text, right-click, and choose Writing Tools from the context menu. It does not fire automatically as you type. For users on macOS 14 Sonoma or earlier, it is not available at all.

The net result is that for the vast majority of Mac users, across all macOS versions, there is no native engine that corrects grammar automatically while typing. A 2023 survey by the macOS productivity research group Setapp found that 71% of Mac users believe their Mac corrects grammar for them - but most of what they experience is spell check, not grammar correction. The two are frequently confused, and the gap is meaningful.

How do Grammarly and LanguageTool compare to real-time correction?

Grammarly and LanguageTool are the two most widely used grammar tools. Both are genuinely excellent at detecting grammar errors. Neither provides real-time correction in the way Charm's Polish does, and understanding why matters for choosing the right tool for your workflow.

Grammarly on Mac is a browser extension. It monitors text in browser-based text fields - Gmail in Chrome, Google Docs in Safari, web forms - and surfaces suggestions in a sidebar panel on the right side of the screen. The suggestions appear as you type, which feels real-time, but the mechanism is different: Grammarly shows you what is wrong and waits for you to click to accept the fix. It does not apply corrections automatically. More importantly, it only works in the browser. Open Apple Mail: no Grammarly. Open your notes app: no Grammarly. Open a desktop messaging client: no Grammarly.

Grammarly does have a Mac desktop app, but it is an editor - a separate window you paste text into for review. It is not a system-wide real-time correction tool. The browser extension is Grammarly's only real-time interface on Mac, and it is confined to the browser.

LanguageTool on Mac follows the same pattern. Its primary Mac delivery mechanism is a browser extension that works inside the browser and offers multilingual grammar suggestions. A desktop app exists but similarly requires you to bring text to it rather than correcting text wherever it lives. LanguageTool does not correct grammar as you type in native Mac apps.

The critical question is: where does your writing actually happen? A 2022 RescueTime study found that knowledge workers spend only 38% of their writing time in browser-based tools. The other 62% happens in native Mac apps - email clients, messaging apps, document editors, note-taking tools, and code editors. A grammar tool that only covers browser text fields leaves the majority of daily writing uncorrected.

How does Charm's Polish feature work?

Charm is a native macOS menu bar app. Its Polish feature is the real-time grammar correction engine that fires while typing. Here is how it works in practice.

Charm uses the macOS Accessibility API to monitor text input system-wide. Unlike tools that hook into specific apps or browsers, the Accessibility API lets Charm observe and modify text across every app on your Mac - mail clients, messaging tools, note apps, document editors, code editors, form fields in any context. One integration covers the entire system.

Polish watches your text as you type. Rather than firing on every keystroke - which would be intrusive and potentially disruptive - it fires at natural sentence boundaries: when you type a period, question mark, or exclamation point. This timing is deliberate. Sentence-end is a natural pause in the writing process, and corrections applied at that point feel seamless rather than interruptive.

When Polish detects a grammar error in the completed sentence, it corrects the sentence in-place and the affected text briefly glows blue. The blue glow distinguishes grammar corrections from spelling corrections (which use a cyan glow from Charm's Spells feature) and word predictions (purple from Oracle). If you want to revert a correction, you can immediately - but in practice, corrections are rarely surprising because they reflect standard grammar rules applied to clear errors.

All processing happens on-device. Polish uses Core ML models that run locally on your Mac's processor, with no network requests and no data leaving your device. This is not a marketing distinction - it is an architectural one. No cloud processing means zero latency from network round trips, and complete privacy regardless of what you are writing.

Polish requires macOS 14 Sonoma or later, and works on both Apple Silicon and Intel Macs. Setup takes under two minutes: download Charm, grant one Accessibility permission in System Settings, and Polish is active immediately.

What grammar errors does real-time correction catch while typing?

Real-time grammar correction targets the errors that appear most frequently in daily writing - the ones that pass spell check and reach recipients uncorrected. Here is what Polish catches while typing.

Subject-verb disagreement. "The results shows a clear pattern" should be "The results show a clear pattern." Both sentences contain only correctly spelled words; the error is structural. Polish identifies the disagreement between the plural subject "results" and the singular verb "shows" and corrects it at sentence end.

Wrong tense. Tense errors are common in long documents where the writer shifts between past and present without noticing. "She finished the report and sends it over" mixes past and present. Polish detects the inconsistency and corrects "sends" to "sent."

Homophone confusion. "Their going to the meeting" passes spell check because "their" is a real word. It is wrong because the sentence needs "they're" (they are). Grammar correction operates at the sentence level and catches this class of error reliably.

Comma splices. Joining two independent clauses with only a comma - "I finished the report, she reviewed it" - is a comma splice. Polish detects the missing conjunction or punctuation and corrects the sentence structure.

Fragment sentences. A sentence without a main verb - "The meeting scheduled for tomorrow." - is a fragment. Polish catches incomplete sentence structures, particularly useful in fast typing contexts where words get dropped.

Research from the Journal of Writing Assessment found that the top five grammar error types in professional writing account for 74% of all grammar errors. Subject-verb agreement, tense inconsistency, and homophone confusion are consistently in the top five. These are precisely the errors that real-time correction while typing eliminates before they leave the writer's keyboard.

How does system-wide coverage change the real-time correction equation?

System-wide coverage is what separates a genuinely useful real-time grammar tool from a partially useful one. The writing tools Mac users interact with span dozens of applications: email clients, Slack or Teams desktop apps, note-taking tools, document editors, code review platforms, web forms, and more. Grammar errors happen across all of them.

A browser-only tool like Grammarly's extension covers the subset of that writing that happens inside the browser. For many Mac users, that is a minority of their daily writing. Native apps - desktop email, desktop messaging, native document editors - are outside Grammarly's reach entirely.

Charm's Accessibility API approach means the same real-time correction that fires in a browser text field also fires in your desktop email client, your desktop messaging app, your note editor, your document tools, and any other application where you type text. The coverage is uniform and universal rather than conditional on which app you happen to be in.

This has a compounding practical benefit: there is nothing to remember. With a browser-only tool, you must remember to open your browser and use the browser-integrated version of whatever service you are writing in. If you prefer to use a desktop app, the tool goes dark. With system-wide correction while typing, the correction is always present regardless of app choice.

Real-time grammar correction for specific use cases on Mac

Business email and professional communication. Grammar errors in client-facing emails are among the most damaging from a credibility standpoint. A Grammarly survey found that 59% of consumers would not use a business with grammar errors on its website - and that credibility effect extends to individual written communication. Real-time correction while typing ensures that errors are eliminated before emails are sent, not caught in a post-send review.

Non-native English speakers. For writers whose first language is not English, grammar is often harder to master than vocabulary. Articles, prepositions, verb agreement, and tense are error-prone areas that native speakers handle intuitively but require explicit attention for second-language writers. Real-time correction while typing provides immediate, in-context feedback at the moment the error is made - the most effective point for learning. A 2019 study in TESOL Quarterly found that immediate, in-context grammar feedback accelerates grammar acquisition significantly faster than delayed or aggregated feedback.

Developers and technical writers. Code comments, commit messages, pull request descriptions, and documentation all live in apps that browser-based grammar tools cannot reach. System-wide real-time correction covers code editors, documentation tools, and every other writing context a developer works in - not just the browser tabs.

Fast typists and heavy writers. The faster you type, the more errors you introduce. For people who type at 80+ words per minute, grammar errors accumulate quickly in long documents. Real-time correction while typing catches errors as they are made rather than letting them pile up into a review pass at the end.

How to set up real-time grammar correction on Mac with Charm

Getting Polish running takes under two minutes. Here is the complete setup process.

Step 1. Go to theodorehq.com/charm and purchase Charm for $9.99. Download the .dmg file after checkout.

Step 2. Open the .dmg, drag Charm.app to your Applications folder, and launch it. macOS will ask you to confirm opening the app on first run.

Step 3. Charm will prompt you to grant Accessibility permission. Click Open System Settings, navigate to Privacy & Security, then Accessibility, and toggle Charm on. Enter your Mac password to confirm. This is the only permission Charm needs.

Step 4. Click the Charm icon in the menu bar. Enable Polish (the grammar feature, shown in blue). You can also enable Spells (spelling correction, cyan) and Oracle (word prediction, purple) independently.

Step 5. Type a sentence with a deliberate grammar error in any app - "She don't know the answer." Complete the sentence with a period. Polish corrects it to "She doesn't know the answer" with a brief blue glow. Real-time grammar correction while typing is now active across your entire Mac.

Charm is compatible with macOS 14 Sonoma and later, on both Apple Silicon and Intel Macs. It requires no account and no internet connection after installation. The one-time $9.99 cost covers up to three Macs and includes all future updates. For a full walkthrough with screenshots, see the dedicated guide to getting grammar correction while typing on Mac.

Real-time correction vs post-edit: what the research says

There is a body of writing research that directly compares real-time and post-edit feedback on writing quality. The findings consistently favour real-time correction for error reduction, though post-edit tools offer advantages for deeper style review.

The core finding from writing studies is that humans catch only about 20% of their own errors when proofreading their own writing. The reason is a well-documented cognitive phenomenon: familiarity with the intended meaning causes writers to perceive their intended words rather than their actual words. Post-edit review tools compensate for this by making errors visible in a structured review, but the correction still depends on the writer noticing and acting on each suggestion.

Real-time correction bypasses the proofreading problem entirely. When a grammar error is corrected at sentence end while typing, no review pass is required for that error. The correction rate for real-time tools is not limited by how carefully the writer proofreads - it is close to 100% for the error categories the tool covers.

The practical workflow implication is that real-time grammar correction while typing eliminates the baseline error rate for covered error types. Post-edit tools then handle the edge cases: stylistic suggestions, complex structural rewrites, and tone improvements that require more context than a real-time engine can apply at sentence end. Many professional writers use both: real-time correction while typing for the first draft, and a post-edit pass for final polish before publishing.

For the full comparison between real-time and post-edit approaches, see the dedicated guide on grammar correction while typing vs post-edit.

Privacy considerations for real-time grammar correction

Because real-time grammar correction monitors keystrokes continuously, the privacy model of the tool matters more than it does for tools you invoke manually. When a grammar tool runs while typing, every sentence you write passes through its correction engine. The question is where that processing happens.

Cloud-based tools like Grammarly process text on remote servers. Every sentence you type in a Grammarly-enabled field is transmitted to Grammarly's servers for analysis. For casual writing - social posts, public emails, general-purpose communication - this trade-off is usually acceptable. For writing that involves client details, financial data, health information, legal matters, or confidential business content, server-side processing is a genuine risk. Many enterprises block Grammarly explicitly for this reason.

Charm processes everything on-device. The Polish grammar engine runs as a Core ML model on your Mac's local processor - Apple Neural Engine on Apple Silicon, or CPU/GPU on Intel Macs. Nothing is transmitted. There is no account to create, no server to communicate with, and no retention of text. A 2023 Identity Theft Resource Center study found that 47% of professionals had concerns about cloud-based tools transmitting sensitive communications. On-device grammar correction removes this concern entirely.

For more on the topic of privacy in grammar tools, see the complete guide to grammar checking on Mac, which covers the privacy models of each major tool in detail.

Frequently asked questions

Does Mac have real-time grammar correction built in?

No. macOS includes spell check but no real-time grammar correction. The native grammar checker in NSSpellChecker requires manual invocation via a right-click menu and only works in apps built with Apple's standard text frameworks. macOS 15 added Apple Intelligence Proofread, but it also requires manual activation - it does not correct grammar while typing.

Does Grammarly fix grammar in real time on Mac?

Grammarly surfaces grammar suggestions in real time inside the browser - but it is a sidebar you must review and click, not automatic correction. More importantly, it only works in browsers. Native Mac apps like Mail, desktop messaging tools, and note apps receive no Grammarly coverage at all. Charm's Polish corrects grammar while typing in every app.

What is Charm's Polish feature and how does it work?

Polish is Charm's real-time grammar correction engine. It uses the macOS Accessibility API to monitor text system-wide and corrects grammar errors at sentence boundaries - when you type a period, question mark, or exclamation point. Corrected text glows briefly blue. Everything runs on-device, with no cloud processing and no data leaving your Mac.

What grammar errors does real-time correction catch?

Real-time correction while typing catches subject-verb disagreement, wrong tense, comma splices, homophone confusion (their/there/they're), missing articles, and fragment sentences. These are the most frequent grammar errors in professional writing - all of which pass spell check because every word is correctly spelled but incorrectly used.

Is real-time grammar correction private?

It depends on the tool. Grammarly sends text to cloud servers for analysis. Charm processes everything on-device using local Core ML models - your keystrokes never leave your Mac. For anyone writing about confidential, legal, medical, or sensitive topics, on-device processing is essential. Charm requires no account and no internet connection after installation.