Grammarlyzer checks common English grammar, spelling, punctuation, and usage issues in the browser. It is built for students, workplace writers, support teams, and anyone revising emails, essays, reports, or web copy before sharing it.
The routine grammar checker runs locally in the browser, so ordinary grammar checks do not require an account. AI Polish is separate: it rewrites a draft only when the user presses the Polish button, and that request may require sign-in and quota checks.
How the Free Checker Fits Real Editing
Use the checker as a first pass over a draft, then review the sentence yourself before accepting changes. The most useful workflow is to catch mechanical issues first: repeated words, misspellings, agreement problems, punctuation warnings, and common confused-word patterns.
For decisions that depend on audience, company style, citation rules, legal wording, or the exact meaning of a sentence, use the linked grammar guides as an explanation layer rather than treating any automated suggestion as final.
What the Checker Can and Cannot Do
The checker is useful for common spelling mistakes, agreement problems, punctuation warnings, repeated words, and frequent confused-word patterns. It cannot fully judge legal meaning, citation style, private company rules, audience intent, or every context-dependent grammar choice. Users should review suggestions before accepting them.
Start with the strongest learning hubs when a suggestion needs explanation: punctuation marks, possessives and contractions, exact homophones, business email vocabulary, and time progression words.
Trust and Review Pages
Read the guide for workflow limits, the privacy policy for data handling, the editorial policy for content standards, and the contact page to report a correction or checker issue.
10 Grammar Rules Every Writer Should Know
These are the grammar rules that appear most often in the corrections the checker flags — and the ones that appear most often in professional and academic writing. Reading these once makes a noticeable difference in draft quality.
1. Subject-verb agreement
The verb must match its subject in number. Singular subjects take singular verbs; plural subjects take plural verbs. Errors happen most often when the subject and verb are separated by a long phrase: "The results of the entire study was surprising" should be "The results of the entire study were surprising" — because the subject is results (plural), not study.
2. Apostrophes in possessives and contractions
An apostrophe signals possession (the team's report) or a contraction (it's = it is). It never signals a simple plural. "The dog's bowl" is possessive. "It's raining" is a contraction. "Three dogs" has no apostrophe. The most common error: writing "it's" when you mean the possessive "its" — pronouns like its, his, hers, and theirs never take apostrophes for possession.
3. Comma splices
A comma splice joins two complete sentences with only a comma: "The deadline is Friday, we need to start now." Fix it with a period, a semicolon, or a comma plus a coordinating conjunction: "The deadline is Friday, so we need to start now." Comma splices are common in informal writing and almost always wrong in professional or academic contexts.
4. Confused word pairs
English has dozens of word pairs that sound similar but mean different things: affect/effect, lay/lie, fewer/less, who/whom, your/you're, their/there/they're. These are among the most common errors in professional writing because spell-checkers do not catch them — both forms are real words. A grammar checker that understands context catches most of these. Learning the decision rule for each pair removes the uncertainty permanently.
5. Run-on sentences
A run-on joins two or more independent clauses without correct punctuation. "The proposal was strong the budget was the problem" is a run-on. Fix it with a period, a semicolon, or a comma and a coordinating conjunction: "The proposal was strong, but the budget was the problem." Long sentences are not automatically run-ons — the issue is missing punctuation between complete clauses, not sentence length.
6. Dangling and misplaced modifiers
A modifier must be placed next to the word it modifies. "Running late, the meeting was started without her" is dangling — the meeting was not running late. Correct: "Running late, she arrived after the meeting had started." Misplaced modifiers cause sentences to say something unintended and can be genuinely confusing to readers who take the sentence at face value.
7. Passive voice (used appropriately)
Passive voice is not wrong — it is misused. "The report was submitted by the team" is passive; "The team submitted the report" is active. Active voice is usually clearer. But passive voice is correct in scientific writing, formal policy language, and situations where the actor is less important than the action. The issue is overuse, not existence: a paragraph full of passive constructions becomes harder to follow and slower to read.
8. Parallel structure in lists
Items in a list should use the same grammatical form. "The project requires planning, execution, and to review the results" breaks parallel structure — it mixes nouns with an infinitive. Correct: "The project requires planning, execution, and review" or "The project requires planning the work, executing the plan, and reviewing the results." Parallel structure makes lists easier to read and signals careful writing.
9. Pronoun-antecedent agreement
A pronoun must agree with its antecedent (the noun it refers to) in number and person. "Every employee should submit their timesheet" uses a plural pronoun for a singular antecedent — this is increasingly accepted in standard usage as a gender-neutral choice, but in formal contexts some style guides still prefer "his or her." Watch for cases where the intended reference is genuinely ambiguous: "When the manager told the assistant that she needed to revise the draft" — which person does she refer to?
10. Tense consistency
Shifting between past and present tense within a paragraph without a clear reason is one of the most common errors in academic writing and long reports. Choose a primary tense for a section and stick to it. Shift only when you are genuinely moving between time frames — describing a past event and then explaining its current relevance, for example. Unintentional tense shifts make prose harder to follow and suggest that the draft was not fully reviewed before submission.
Essential Grammar Topics
These guides cover the grammar questions that appear most often in the checker's suggestions. Each one explains the rule, shows the common mistake, and gives you the decision test you need to apply it correctly in your own writing.
When to use a comma before "and," how to punctuate introductory phrases, and the rules for setting off non-essential clauses — the four most common comma decisions in professional writing.
The full range of agreement cases including collective nouns, indefinite pronouns, compound subjects, and the tricky patterns that separate the subject from its verb with a long phrase.
One of the most common errors in professional writing. The rule is simple once you know it: the apostrophe signals "it is," never possession for the pronoun.
Affect is usually a verb; effect is usually a noun. A quick substitution test removes the ambiguity for almost every case you will encounter in everyday writing.
Another apostrophe contraction pair that spell-checkers miss. You're = you are. Your = possessive. The test is always: can I read this as "you are"?
When to prefer active, when passive is correct and even necessary, and how to recognize the passive construction so you can make a deliberate choice rather than an accidental one.
Browse all grammar topics in the Learn section, organized by category: confused word pairs, punctuation, sentence structure, verb tenses, and writing vocabulary.