A calm grammar tool, not another red-line factory.

The grammar checking core is powered by Harper, an open-source English grammar engine written in Rust. Harper runs as a WebAssembly (WASM) module in your browser tab. The engine files must download and initialize before the first check; timing varies with the device, browser, cache, and network.

For the routine web grammar check, draft text is processed by the Harper engine in the browser instead of being sent to a Grammarlyzer application server. The page still loads hosting assets and may use analytics or advertising services, which can receive the limited technical data described in the privacy policy.

Because the engine lives inside the browser tab, the checker can flag common mechanical issues without sending draft text to a Grammarlyzer server. Suggestions are still suggestions: context, audience, and specialized style rules remain decisions for the writer.

Every grammar guide on Grammarlyzer starts from a real writing problem: a confused word pair that trips up careful writers, a punctuation rule people apply inconsistently, a structural pattern that makes sentences harder to follow. Topics are chosen based on what causes repeated confusion in emails, academic writing, and professional documents — not what fills a chapter in a traditional grammar textbook.

Each guide is written to answer the specific question a writer faces at the keyboard. For a confused-word page like affect vs. effect, that means showing the decision rule, a quick test the writer can apply without memorizing linguistic categories, the most common mistake with a workplace or school example, and the edge cases where the rule gets more complicated. For a punctuation guide like comma usage before a conjunction, it means explaining each pattern with the sentence type that requires it, rather than listing seven abstract principles and leaving the application to the reader.

Guides are reviewed against their own examples, not just edited for tone. If an example uses a rule inconsistently, the example is rewritten. If an explanation could be read two ways, the explanation changes. If a common exception is missing, a section is added. The standard is whether a writer who is actively revising a real document would leave the page knowing what to do differently the next time they face that grammar decision.

The Learn section covers more than 100 grammar topics organized by category: confused word pairs, punctuation rules, sentence structure, verb tenses, modal verbs, pronoun usage, and vocabulary for specific writing contexts like academic papers and business emails. Topics that share conceptual territory are linked together so a writer who arrives with one question can find related guidance without starting a new search.

The checker can flag common mechanical patterns including misspellings, some subject-verb agreement failures, doubled words, confused word pairs in the Harper rule set, punctuation spacing, and apostrophe errors. Coverage depends on the exact sentence, so each suggestion should be reviewed before it changes a draft.

The checker is not a substitute for a professional copy editor, a legal reviewer, a writing instructor, or an academic tutor. For context-dependent questions — whether passive voice serves a particular sentence better than active, which citation format an institution requires, whether a legal disclaimer needs rewording for a specific jurisdiction, whether a sentence's tone is right for its audience — the checker is a starting point, not the final word. These are judgment calls that depend on knowledge the checker does not have.

Grammar guides on Grammarlyzer reflect standard edited American English as documented in major usage references. When a rule is genuinely contested among careful writers, the guide says so. When two forms are correct in different contexts, the guide explains the context rather than declaring one form wrong. Grammar is descriptive before it is prescriptive, and guides that pretend otherwise train writers to apply rules incorrectly to sentences where the stricter form is not required.

If you find an error in a guide — a wrong example, an overclaim, a missing exception, a broken link — use the contact page to report it. We update and correct pages when the issue is clearly identified. The standard for a published guide is whether it would help a real writer make a better decision on a real document, not whether it sounds authoritative in isolation.

Grammarlyzer publishes and maintains the guides under the product name. Automated validators check page structure, metadata, links, and recorded audit fields. Those checks are useful release gates, but they are not a substitute for a person reviewing grammar claims and examples.

Some guides link directly to public dictionaries, usage notes, or writing references for material rules and exceptions. When sources disagree or advice changes by register, dialect, discipline, or house style, the page should explain that context rather than declare one form universally correct.

The Harper checker and the Learn section serve different jobs: the tool flags patterns, while a guide should explain the decision and its limits. A recorded engine example proves only that exact input and environment, not every sentence in the topic.

Drafting, research, and quality checks may use AI-assisted tools. A page is described as human-reviewed only when the owner has recorded that review; the publisher byline alone does not make that claim. Full details are in our editorial policy.