Questions, answered.

Yes. The grammar checker is free forever, with no signup. AI Polish has a free monthly quota; sign-in is only required the moment you press the Polish button.

No. Grammar checking is browser-local — your text never leaves the device for routine checks. AI Polish only sends the draft on a single request, and the request isn't logged against your account.

It catches the common 80% — spelling, agreement, confused word pairs, and the most frequent style issues. For nuanced edits involving audience, tone, or legal meaning, you would still want a human reviewer or AI Polish.

Yes. The web app is fully responsive and works on any modern browser. We also have a native Flutter app for iOS and Android that uses the same engine.

No limit on the free grammar checker. AI Polish quotas vary by plan, but the free tier handles 15 rewrites a month. For very large documents, working section by section gives the fastest results.

We prioritize quiet over volume. One reason per issue, no red-line storms. And we keep the checker entirely browser-local by default — most competitors send every keystroke to a server.

Yes. The Formal polish tone is tuned for emails, reports, proposals, and other professional contexts. It removes wordy phrases and passive constructions that weaken professional writing.

No. It runs in any modern browser with no installation or signup. If you want it on your phone or desktop natively, the mobile app is in the Play Store and App Store.

The checker catches spelling errors (typos, doubled letters, high-frequency misspellings), subject-verb agreement problems, tense inconsistencies, repeated words, confused word pairs (such as affect/effect, its/it's, their/there/they're, your/you're), punctuation issues (wrong apostrophes, missing commas, spacing errors around punctuation), and common style problems like wordiness or unnecessary passive constructions. It does not catch errors that require understanding audience, intent, citation style, legal meaning, or private company conventions. Those judgment calls are better reviewed by a human editor or handled with the AI Polish feature, which rewrites rather than flags.

The routine grammar checker runs entirely inside your browser using WebAssembly (WASM). Your text never leaves your device during a standard grammar check — there is no server call, no keystroke logging, and no storage of your drafts. AI Polish is the one exception: when you press the Polish button, a snapshot of your current draft is sent to an AI rewriting service to generate the polished version. This is an explicit action you initiate, not a background process. We do not use your text to train AI models. The full data handling details are in the privacy policy.

The grammar checker identifies specific mechanical issues — a misspelling, a wrong apostrophe, a subject-verb mismatch — and suggests targeted corrections one at a time. It runs locally in your browser with no sign-in required. AI Polish is a separate feature that rewrites your entire draft in a consistent tone (Formal, Casual, or Concise). It changes more than grammar: it adjusts vocabulary, sentence structure, and phrasing throughout the draft. AI Polish requires a brief sign-in because it uses server-side AI processing, and the free plan includes a monthly quota of rewrites. For most writing tasks, the grammar checker is sufficient. AI Polish is most useful when a draft needs significant tonal work beyond mechanical corrections.

Yes, and it is particularly useful for non-native English writers. English grammar has counterintuitive rules around articles (a/an/the), prepositions (in/on/at), verb tenses, and commonly confused word pairs that native speakers learn through years of exposure. The checker catches many of these mechanically, and the paired grammar guides explain the rule in plain English without relying on linguistic terminology. If you see a correction and want to understand why it is right, the linked guide gives you the decision rule and examples in context. Regular use of the checker and the grammar guides together tends to improve writing accuracy more than the checker alone, because you learn the rule that the checker is applying.

Affect is almost always a verb meaning to influence or have an impact on something: "The weather affects driving conditions." Effect is almost always a noun meaning the result or outcome: "The effect of the policy change was significant." A quick test: if you can replace the word with "influence" (as a verb), use affect. If you can replace it with "result" or "outcome," use effect. There are rare exceptions where effect is used as a verb (meaning to bring about) and affect as a psychology noun, but these are uncommon in everyday writing. See the full affect vs. effect guide for examples in context.

Use a comma before "and" in two main situations. First, when joining two independent clauses (sentences that could each stand alone): "She finished the report, and he submitted it before the deadline." Without the comma here, the sentence can be harder to follow. Second, when writing a list of three or more items, many style guides recommend a comma before the final "and" — this is called the Oxford comma or serial comma: "We need pens, paper, and staples." Whether to use the Oxford comma is a style choice, but you should apply it consistently throughout a document. The comma is not required before "and" when it joins only two words, phrases, or short clauses that are clearly connected: "She typed and proofread the document."

Subject-verb agreement means the verb in a sentence must match its subject in number. A singular subject takes a singular verb; a plural subject takes a plural verb. "The team is ready" (singular team, singular is) vs. "The teams are ready" (plural teams, plural are). This seems simple, but errors are common when the subject and verb are separated by a long phrase — "The result of all our experiments and analyses was surprising" — or when collective nouns, indefinite pronouns, or compound subjects are involved. Subject-verb agreement errors are noticeable to readers and can undermine the credibility of professional writing. The grammar checker catches the most common patterns. For the full range of exceptions, see the subject-verb agreement guide.

Passive voice occurs when the subject of the sentence receives the action rather than performs it: "The report was submitted by the team" (passive) vs. "The team submitted the report" (active). Active voice is usually clearer and more direct. However, passive voice is not always wrong — it is correct and appropriate in scientific writing (where the focus is on what was done, not who did it), in formal policy documents (where the actor is deliberately unspecified), and in situations where the recipient of the action matters more than the actor. The guidance to "avoid passive voice" is about overuse, not absolute elimination. If passive voice appears in a sentence where it genuinely serves the meaning, keep it. If it appears because you instinctively wrote around the actor, active voice is probably clearer. The active vs. passive guide covers the full range of cases.

It's (with apostrophe) is always a contraction of "it is" or "it has." If you can read the sentence with "it is" in place of the word and it still makes sense, use it's: "It's raining" = "It is raining." Its (no apostrophe) is the possessive form — it shows that something belongs to "it": "The company released its annual report." The apostrophe rule for possessives does not apply to pronouns in English, which is why its, his, hers, theirs, and whose are all written without apostrophes. Confusing its/it's is one of the most common errors in professional writing. The grammar checker flags it reliably. See the its vs. it's guide for more examples.

Use fewer with countable nouns — things you can count individually: "fewer mistakes," "fewer words," "fewer employees." Use less with uncountable (mass) nouns — things measured in bulk or degree: "less time," "less traffic," "less effort." The quick test: if you can put a number directly in front of the noun, use fewer. "Three fewer mistakes" works; "three less mistakes" does not. Common exceptions include distances, amounts of money, and time periods, which conventionally use less even though they involve numbers: "less than five miles," "less than fifty dollars." The fewer vs. less guide covers the full rule and the exceptions in detail.

A run-on sentence occurs when two or more independent clauses are joined without proper punctuation or a coordinating conjunction. "The report was due Friday the team finished it Thursday" is a run-on. There are four ways to fix a run-on: (1) Use a period to make two sentences. (2) Use a comma and a coordinating conjunction (and, but, so, yet, or, nor, for): "The report was due Friday, and the team finished it Thursday." (3) Use a semicolon to join closely related clauses: "The report was due Friday; the team finished it Thursday." (4) Use a subordinating conjunction to show the relationship: "Because the report was due Friday, the team finished it Thursday." Which fix is best depends on the meaning and the rhythm of the surrounding text. The run-on sentences guide covers each option with examples.

Yes. Starting a sentence with "And," "But," or other coordinating conjunctions is grammatically acceptable in standard English. The rule against it was a prescriptive teaching convention, not a grammatical law, and major style guides including the Chicago Manual of Style and AP Stylebook confirm that these sentence-starters are fine. Good writers use them deliberately for emphasis or to create a particular rhythm: "The proposal was strong. But the budget was the problem." However, starting every third sentence with "And" or "But" becomes a stylistic tic that weakens writing. Use these openers when the contrast or addition genuinely calls for the emphasis a sentence break provides, not as a default way to connect ideas.

The Oxford comma (also called the serial comma) is the comma placed before "and" or "or" in a list of three or more items: "We ordered coffee, tea, and water." Without it: "We ordered coffee, tea and water." Both are grammatically correct, but omitting the Oxford comma can occasionally create ambiguous readings. The famous example: "I'd like to thank my parents, Ayn Rand and God" (without Oxford comma) could be read as naming Ayn Rand and God as the parents. With the Oxford comma: "I'd like to thank my parents, Ayn Rand, and God." Most American style guides (Chicago, APA) recommend the Oxford comma. AP style omits it. The most practical advice: pick one approach and apply it consistently throughout a document. Grammarlyzer does not enforce a preference on the Oxford comma because it is a style choice, not a grammar rule.

Who is a subject pronoun — it performs the action. Whom is an object pronoun — it receives the action. A practical test: replace the word with "he" or "him." If "he" sounds right, use who. If "him" sounds right, use whom. "Who wrote the report?" → He wrote the report → use who. "To whom should I address this?" → I should address this to him → use whom. In casual speech, "who" is widely used for both cases and sounds natural. In formal writing, getting who/whom right is worth the extra check. See the who vs. whom guide for more examples and the subordinate clause cases that trip up careful writers.

Use a semicolon in two main situations. First, to join two closely related independent clauses without a coordinating conjunction: "The deadline is Friday; the report is not finished." Both clauses could stand alone as sentences — the semicolon signals that they are closely connected in meaning. Second, to separate items in a list when the items themselves contain commas: "The attendees were Sarah Kim, director of operations; James Park, lead engineer; and Ana Santos, project manager." Using commas in that list would be ambiguous. A semicolon is not interchangeable with a colon. A colon introduces something — a list, an explanation, a quotation. A semicolon connects two equal, related clauses. If you can replace the semicolon with "and" or a period and it reads correctly, you are probably using it right.

No. A grammar checker catches mechanical errors reliably — misspellings, wrong apostrophes, agreement failures, confused word pairs. A human editor catches these and more: whether the argument is clear, whether the tone is right for the audience, whether the structure serves the purpose, whether a sentence is technically correct but needlessly confusing, and whether a claim is accurate. Grammar checking is a first pass, not a substitute for editing. For everyday writing — emails, reports, social posts — a grammar checker is often sufficient once you have reviewed the suggestions. For documents where the stakes are high — published articles, legal agreements, academic submissions, investor communications — a human editor or a careful self-editing pass with the grammar guide alongside is the more reliable approach.