Limato
Comma Checker
Paste a sentence or a full draft and get every comma where English wants it — with the rule behind each fix. Your wording is untouched. Free, no signup.
How to use the comma checker
Paste up to 750 words and click Check Commas. The corrected text comes back with every change highlighted, so you can see which comma appeared, which one was deleted, and which one moved. Sentences that were already punctuated correctly come back untouched, and your wording never changes — this is a punctuation fix, not a rewrite. Your text is processed and returned, never stored.
The sections below are the six rules that account for almost every comma this tool touches. If you want the whole punctuation set instead — apostrophes, capitalization, quotation marks, run-ons — use the punctuation checker; if the sentence has grammar problems too, the grammar checker handles both in one pass.
Rule 1: comma splices — two sentences joined by a comma
The single most common comma error, and the one that most often survives every spell checker. A comma cannot join two things that could each stand alone as a sentence.
Wrong: "I sent the report on Friday, she never replied."
Four legitimate fixes, in rough order of how often they're right:
- Period. "I sent the report on Friday. She never replied."
- Comma plus a coordinating conjunction. "I sent the report on Friday, but she never replied."
- Semicolon, when the two halves are tightly linked. "I sent the report on Friday; she never replied."
- Subordinate one half. "Although I sent the report on Friday, she never replied."
Watch out for however, therefore, and then: they are adverbs, not conjunctions, so "I sent it, however she never replied" is still a splice.
Rule 2: comma after an introductory phrase
When a sentence opens with anything before the main subject — a time phrase, a place, a condition, a participle, a transition word — that opener takes a comma.
- "After the meeting, we changed the deadline."
- "In 2024, the team doubled."
- "Because the client cancelled, we lost the quarter."
- "However, the numbers disagree."
- "Having read the contract, she signed it."
With very short openers ("Yesterday we shipped") the comma is optional and many writers drop it. With long ones it isn't optional: without the comma, "After the meeting with the client the team" makes the reader parse "the client the team" before backing up. Flip the order and the comma disappears: "We changed the deadline after the meeting."
Rule 3: commas around non-essential clauses
This is the one where commas change the meaning rather than the rhythm. If a clause could be deleted without changing which thing you're talking about, it gets commas on both sides. If deleting it changes which thing you mean, it gets none.
- Non-essential: "My manager, who sits next to me, approved it." You have one manager; the clause is extra detail.
- Essential: "The manager who sits next to me approved it." It picks out which manager, so no commas.
The half-comma is the classic error: "My colleague who joined in March, agreed" — one comma, which is always wrong. Either both or neither. The same logic covers appositives ("Our CTO, Ana, will present") and the difference between which (usually non-essential, commas) and that (essential, no commas).
Rule 4: comma before and, but, or so
Put a comma before a coordinating conjunction (and, but, or, nor, for, so, yet) when it joins two complete sentences:
- "We shipped the feature, and the support tickets dropped." — two full sentences, comma stays.
- "We shipped the feature and dropped the old one." — one subject, two verbs, no comma.
That second case is where most extra commas come from: "I reviewed the draft, and sent it back" doesn't need one. If what follows the conjunction has no subject of its own, don't put a comma in front of it.
Rule 5: the serial comma (Oxford comma)
The comma before the final and in a list: "drafts, edits, and approvals." Both styles are correct — American editing usually keeps it, British and journalistic style often drops it — so this tool doesn't force a house style on you. It keeps whichever one your text already uses and makes it consistent across the document.
One case where you want it regardless: when leaving it out creates a false pairing. "I thanked my co-founders, Ana and Marc" reads as though Ana and Marc are the co-founders. "I thanked my co-founders, Ana, and Marc" doesn't.
Rule 6: commas English refuses
Removing commas is half the job. English rejects several that other languages require or tolerate:
- Before that. "He said, that the deadline moved" — no comma, ever, when that introduces the clause.
- Between subject and verb. "The team that shipped the release last quarter, deserves a bonus" — never, no matter how long the subject gets.
- Between verb and object. "She announced, the new pricing" — no.
- Before because, in most sentences: "We delayed the launch because the API wasn't ready."
- After a greeting in the American style. "Dear Ana," takes a comma; "Dear Ana:" is the formal alternative, but "Dear Ana" with nothing at all is the actual error.
- Between two adjectives that aren't coordinate. "a large, blue button" is fine; "a large, software company" is not — try swapping them or inserting and, and if it sounds wrong, drop the comma.
Comma habits that transfer wrong from your first language
Most comma errors in non-native English aren't carelessness — they're a rule from another language applied faithfully:
- Spanish, Russian, German, Italian: a comma can join clauses that English forces apart. Spanish "Envié el informe, no me contestó" is fine; the word-for-word English is a comma splice. This is the single biggest source of splices we correct.
- Spanish and Italian que / che, German dass, Russian что: a comma before the subordinator is normal or mandatory there. In English, no comma before that.
- Decimal commas. "2,5%" and "1.000 users" are correct across most of Europe and wrong in English: "2.5%" and "1,000 users". The separators are swapped.
- German relative clauses always take commas; in English, only the non-essential ones do (Rule 3).
- French spacing. No space before a comma, and none before ? ! : ; either.
Spanish writers can check the Spanish rules on the corrector de comas. For the wording habits that mark text as non-native even when every comma is right, see 12 ESL patterns native speakers never use — or run the draft through the tone checker.
Fix commas anywhere you write
Limato's Chrome extension corrects and rewrites text inline on any website — Gmail, Slack, LinkedIn, Notion. Highlight, fix, paste back. 20 free rewrites a day.
Add to Chrome — FreeFrequently asked questions
Where does the comma go in this sentence?
Paste the sentence above and click Check Commas — the corrected version comes back with each added, moved, or deleted comma highlighted, so you can see which rule applied. It works on a single sentence or a full draft, up to 750 words per check.
Is the comma checker free?
Yes. Checks on this page are free with a daily limit, no signup. The Limato Chrome extension gives 5 free rewrites a day without sign-in, or 20 a day with a free Google account.
What is a comma splice?
Two complete sentences joined with only a comma: "I sent the report, she never replied." Fix it with a period, a semicolon, a comma plus a conjunction ("...report, but she..."), or by subordinating one half ("Although I sent..."). Note that however, therefore, and then are adverbs, not conjunctions, so they don't fix a splice.
Do I need the Oxford comma?
Both styles are correct. American editing usually keeps the comma before the final and; British and journalistic style often drops it. This checker keeps whichever your text already uses and makes it consistent — except where dropping it creates a false pairing, as in "I thanked my co-founders, Ana and Marc".
Do you put a comma before and?
Only when what follows is a complete sentence with its own subject: "We shipped it, and tickets dropped." With a shared subject there's no comma: "We shipped it and dropped the old one."
How is this different from the punctuation checker?
Same engine, narrower focus. This page is about commas and the rules behind them. The punctuation checker covers the full set — apostrophes, capitalization, quotation marks, run-ons, semicolons, dashes — and fixes commas along the way. Use this one when commas are the actual problem.
Is my text stored?
No. Text is sent to the rewrite API, processed, and returned — not stored, logged, or used to train models.