Free Run-on Sentence Checker
Paste your text and see every run-on, comma splice and fused sentence — fixed with the lightest edit that makes it read right.
Run-on Sentence Checker editor
Why use this run on sentence checker?
How to use the run-on sentence checker
Paste your text
A paragraph or a whole essay — the checker reads clause boundaries across the entire text.
Click “Fix Run-ons”
Every fused sentence and comma splice is repaired; correctly punctuated sentences are left untouched.
Review and copy
Use the explanations mode to see each run-on quoted alongside the repair that was applied.
About this run on sentence checker
A run-on sentence is not a long sentence — it is two complete sentences pushed together without the punctuation to separate them. That distinction matters, because most advice on the subject (“break up your long sentences”) fixes the wrong thing and flattens prose that was fine. This free run-on sentence checker looks at clause boundaries instead, so it finds real run-ons and leaves your long-but-correct sentences alone.
Two forms get caught. A fused sentence runs two independent clauses together with no punctuation at all. A comma splice joins them with only a comma — the more common error, and the one graders mark most often. The checker names which it found and repairs it with the smallest change that works: a period, a semicolon, a conjunction, or subordination.
Switch to the explanations mode to see each run-on quoted next to its repair. Run-ons are one of the few writing errors that genuinely disappear once you can see the clause boundary, so a few sessions with the explanations on tends to be enough.
