What a comma splice is
A comma splice joins two independent clauses with only a comma. «The results were inconclusive, the authors repeated the experiment.» Each half can stand alone as a sentence, so the comma is too weak a join. It is the most common punctuation error that spell-check does not catch.
A comma splice is one kind of run-on sentence. If you also want to check for fused sentences with no punctuation at all, use the run-on sentence checker.
Four ways to fix a comma splice
Take «The experiment failed, we changed the protocol.»:
- Full stop: «The experiment failed. We changed the protocol.»
- Semicolon: «The experiment failed; we changed the protocol.»
- Comma plus conjunction: «The experiment failed, so we changed the protocol.»
- Subordinate one clause: «Because the experiment failed, we changed the protocol.»
Choose by how closely the two ideas connect. A full stop gives them equal weight; a conjunction or subordinating word shows the relationship.
When a comma is correct
Not every comma between two clauses is a splice. These are fine, and the checker is built to leave them alone:
- A fronted phrase: «In this study, we investigated feedback.»
- A comma plus and, but, so, or, yet: «The sample was small, and power was limited.»
- An appositive or relative clause: «Smith, a professor at Yale, argued the effect was overstated.»
What this checker cannot see
This tool uses browser-based rules, not a full grammatical parser. It is designed to decline rather than guess, so it can miss a splice in an unusual sentence. No flags is not a guarantee of correct punctuation.
Take it further with Diglot
This free tool runs in your browser. When you want to act on what it shows — fix the grammar, tighten the phrasing, or make your English read like a native wrote it — that is what Diglot is built for. The free tier is meaningful for daily writing, no card required.
Frequently asked questions
- What is a comma splice?
- A comma splice is two independent clauses joined by only a comma, for example «I arrived early, the doors were locked». Each half could stand alone as a sentence. Fix it with a full stop, a semicolon, a comma plus a conjunction such as and, but or so, or by making one clause subordinate.
- Is a comma splice the same as a run-on sentence?
- A comma splice is one type of run-on sentence. The other type is a fused sentence, which joins two independent clauses with no punctuation at all. This checker looks for comma splices; the run-on sentence checker also flags long clause joins that may be fused sentences.
- Is a comma splice ever acceptable?
- In formal and academic writing, treat it as an error. In some informal or literary writing, short parallel clauses are joined by commas on purpose («I came, I saw, I conquered»). If you are writing for a course, a journal or an employer, use one of the four fixes.
- Why does this checker not flag a comma after an introductory phrase?
- A comma after a fronted phrase, such as «In this study, we investigated…», is required, and the part before the comma is not a full clause. The checker only flags a comma when both sides are independent clauses.
- Is my text uploaded or stored anywhere?
- No. The comma splice checker runs 100% in your browser using client-side JavaScript. Your text is private and never leaves your device.
