Best AI Grammar Checker Browser Extensions

Why Browser Extensions Are the Most Useful Grammar Checker Format

A browser extension is the single most effective way to use a grammar checker because it works everywhere you type on the web without requiring you to copy text into a separate app. Email, documents, social media posts, chat messages, forum replies, CMS editors, project management tools, and every other web-based text field are covered by one installation. You install the extension once, and grammar checking happens automatically across every site you visit.

The alternative workflow, copying text from your writing app into a grammar checker's website, checking it, copying the corrected text back, is tedious enough that most writers skip it for anything shorter than a formal document. Browser extensions eliminate that friction entirely. Errors are underlined as you type, suggestions appear with a click or hover, and corrections are applied in place without any copy-paste steps. This means your casual writing, the quick email replies, Slack messages, and social media posts that you would never bother to paste into a grammar checker, gets checked automatically.

Most grammar checker companies treat the browser extension as their primary product, investing more engineering resources into extension development than into their standalone web apps. The extension is where the majority of their users interact with the product daily, which means it receives the most frequent updates and the most polished user experience.

Grammarly for Chrome: Best Overall Extension

Grammarly's Chrome extension is the benchmark against which every other grammar checker extension is measured. It works in Gmail, Google Docs, LinkedIn, Twitter/X, Facebook, Reddit, Slack (web version), Notion, WordPress, Medium, and virtually every other web-based text input, including custom CMS editors and web applications built with standard HTML form elements. The extension detects text fields automatically and begins checking as you type without requiring activation.

Suggestion speed is where Grammarly separates from competitors. Errors are underlined within one to two seconds of typing, with correction options appearing instantly when you click or hover over the underline. This near-instant feedback means the tool keeps up with normal typing speed without creating distracting delays. ProWritingAid and LanguageTool extensions both take slightly longer to surface suggestions, which can feel sluggish in comparison after you have used Grammarly.

The extension includes a floating assistant icon that appears in the corner of text fields, showing the total number of suggestions and providing a one-click overview. Clicking the icon opens a panel that lists all suggestions in order, allowing you to review and apply corrections sequentially rather than hunting for individual underlines in a long document. This batch review mode is useful for checking longer emails and documents where scrolling through the text to find each underline would be inefficient.

The free tier checks spelling, basic grammar, and punctuation. Premium adds style suggestions, tone detection, full-sentence rewrites, vocabulary enhancement, and plagiarism checking, all accessible directly within the extension without opening a separate window or navigating to Grammarly's website.

Browser support:

Chrome, Firefox, Edge, Safari, and Brave. The Chrome extension also works in Chromium-based browsers like Opera and Vivaldi.

Known limitations:

Grammarly does not work in some web-based code editors (VS Code for web, CodeMirror-based editors), encrypted email platforms (ProtonMail), and a few proprietary web applications that use non-standard text input methods. It also does not work in Google Sheets cells, which use a different rendering engine than standard text fields.

LanguageTool for Chrome: Best for Multilingual and Privacy

LanguageTool's browser extension checks grammar in over 30 languages, making it the only grammar checker extension that is genuinely useful for writers who work in multiple languages throughout the day. Switching between languages is automatic: the extension detects the language of the text being typed and applies the appropriate grammar rules without manual language selection. If you write an email in English, switch to German for a message to a colleague, and then draft a social media post in Spanish, the extension handles all three languages seamlessly.

The extension works in Gmail, Google Docs, LinkedIn, Twitter/X, Outlook Web, WordPress, and most standard web text fields. Error detection speed is slightly slower than Grammarly's, typically three to four seconds after typing stops, but fast enough to be useful in real-time writing. Suggestions appear as colored underlines with correction options on click, following the same interaction pattern that Grammarly popularized.

Privacy is a genuine advantage. LanguageTool's extension can be configured to process text locally rather than sending it to LanguageTool's servers, though local processing limits the AI-powered suggestions to the rule-based engine only. For users who handle sensitive documents and want grammar checking without any data leaving their browser, this local-only mode is unique among grammar checker extensions. The Premium plan also offers a self-hosted server option for organizations that want the full AI-powered checking without sending data to LanguageTool's cloud.

The free tier supports 10,000 characters per check, which is sufficient for individual emails and messages but may require splitting longer documents. The Premium plan at $4.99 per month removes the character limit and adds the "picky mode" with additional style suggestions.

Browser support:

Chrome, Firefox, Edge, Safari, and Opera.

Known limitations:

The extension does not detect language as quickly in very short text fields (fewer than 20 words), occasionally defaulting to the wrong language for brief messages. Style-level suggestions in the free tier are minimal compared to Grammarly's free tier. The correction panel is less polished than Grammarly's, with fewer visual cues about suggestion severity.

ProWritingAid for Chrome: Best for Detailed Reports

ProWritingAid's browser extension provides the same grammar checking found in its desktop app, with real-time underlining and correction suggestions in web text fields. The extension works in Gmail, Google Docs, LinkedIn, and most standard web editors. Where it stands apart is the ability to open a full analysis view that generates ProWritingAid's detailed writing reports, including overused words, sentence length variation, readability scores, and sticky sentences, directly from text selected in the browser.

This full analysis view is not available in Grammarly's or LanguageTool's extensions. If you are drafting a long email or writing content directly in a CMS editor and want to check not just grammar errors but also writing quality patterns, ProWritingAid's extension provides that analysis without requiring you to copy text to a separate app. The reports are the same ones available in the desktop app, just rendered within the browser extension panel.

The tradeoff is speed. ProWritingAid's extension is the slowest of the three major options, with suggestions taking three to six seconds to appear after typing stops. In quick-reply contexts like chat messages and short emails, this delay makes the tool feel unresponsive. For longer writing sessions where you pause between paragraphs anyway, the delay is less noticeable. The analysis reports also take several seconds to generate, which is expected given the depth of analysis but still slower than Grammarly's instant feedback.

The free tier allows limited checks per day. The Premium plan ($10 per month annually or $399 lifetime) unlocks unlimited checks and the full report suite. There is no middle tier between free and Premium.

Browser support:

Chrome, Firefox, Edge, and Safari.

Known limitations:

Slower suggestion speed than Grammarly and LanguageTool. The extension can cause noticeable slowdown on pages with very large text fields or complex web editors. The writing reports, while powerful, are less useful for short-form writing where document-level patterns are not relevant.

Microsoft Editor for Edge and Chrome: Best Built-In Option

Microsoft Editor is a free browser extension from Microsoft that checks spelling, grammar, and basic style across web text fields. For users who already use Microsoft Edge, many of Editor's features are built directly into the browser without requiring a separate extension installation. The Chrome extension provides the same functionality for Chrome users.

The detection quality covers basic errors reliably: misspellings, subject-verb agreement, capitalization, and common punctuation mistakes. Style suggestions are limited compared to Grammarly and ProWritingAid, primarily flagging passive voice, wordiness, and informal language in formal contexts. The tool does not offer tone detection, full-sentence rewrites, or document-level consistency analysis.

The main advantage is friction reduction. Edge users get grammar checking without installing anything. Chrome users install one extension from Microsoft, a company they likely already trust with their data through Microsoft 365. The extension works in Gmail, Outlook Web, LinkedIn, and standard web text fields. For Microsoft 365 subscribers, the extension provides enhanced suggestions that leverage the same AI capabilities as Copilot, though these advanced features are only available with an active Microsoft 365 subscription.

Browser support:

Edge (built-in), Chrome, and Firefox.

Known limitations:

Style suggestions are basic compared to dedicated grammar checkers. No multilingual grammar checking (English only for grammar, though spelling is supported in additional languages). The enhanced AI features require a Microsoft 365 subscription, limiting the free version to basic corrections.

Running Multiple Extensions Together

Some writers install two grammar checker extensions to catch more errors through overlapping coverage. The most common combination is Grammarly plus LanguageTool, which provides Grammarly's strong style coaching for English alongside LanguageTool's multilingual support for other languages. This combination generally works without conflicts in most web applications.

However, running multiple grammar checker extensions simultaneously can cause issues. Both tools may underline the same error with different colors, creating visual clutter. Suggestion popups may overlap or interfere with each other. In some web editors, particularly those with custom text rendering like Notion or Confluence, two active grammar checker extensions can cause input lag, cursor positioning errors, or visual glitches.

The practical solution is to set one extension as your primary (active on all sites) and the other as secondary (disabled by default, enabled manually for specific documents or languages). Both Grammarly and LanguageTool allow per-site enabling and disabling through their extension settings, making this workflow manageable without constantly visiting the extensions menu.

Performance and Privacy Considerations

Grammar checker extensions send your text to remote servers for analysis, with the exception of LanguageTool's local-processing mode. This means that everything you type in a checked text field, including email content, chat messages, and document drafts, is transmitted to the grammar checker's servers. For most users, this is an acceptable tradeoff. For writers handling confidential information, legal documents, medical records, or classified material, it is a serious privacy concern.

Grammarly's privacy policy states that text is processed for grammar checking and then deleted, but the text is temporarily stored on Grammarly's servers during processing. LanguageTool's local mode avoids this entirely by running all analysis in the browser. ProWritingAid and Microsoft Editor both process text on their respective servers.

All grammar checker extensions add some memory and CPU overhead to the browser. Grammarly's extension uses approximately 50 to 100 MB of RAM in active use, which is noticeable on machines with limited memory but negligible on modern systems with 8 GB or more. LanguageTool and ProWritingAid have similar resource footprints. If you notice browser slowdown after installing a grammar checker extension, check your browser's task manager (Shift+Esc in Chrome) to see how much memory the extension is consuming.