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Run On Sentence Checker
The Run On Sentence Checker instantly flags comma splices and fused sentences in any text, showing exactly which sentences are problematic and giving you three concrete ways to fix each one. Paste your writing and get real-time feedback — no sign-up, no data sent to servers, completely free.
Who Is It For?
Students
Catching run-on sentences in essays, reports, and assignments before submission.
ESL / EFL Learners
Learning the difference between independent clauses and how to punctuate them correctly.
Content Writers & Bloggers
Ensuring articles and blog posts are clear, readable, and grammatically sound.
Editors & Proofreaders
Quickly scanning client documents for structural sentence issues before final review.
How It Works
Paste or type your text into the editor on the left. The checker scans every sentence in real time, detecting comma splices (two independent clauses joined by only a comma) and excessively long fused sentences. Each detected issue appears in the right panel with a badge, a quoted excerpt, a plain-English explanation of the problem, and three numbered suggestions for how to fix it. Use the arrow controls or the dot navigation to move through multiple issues.
Features
- Real-time run-on sentence detection as you type
- Comma splice detection with subject-verb pattern analysis
- Long/fused sentence detection for 45+ word sentences
- Numbered fix suggestions for every issue found
- Issue type badges: Comma Splice vs. Long Sentence
- Navigate multiple issues with arrow controls and dot indicators
- Sample text to demonstrate the tool instantly
- Word and character count in the footer
- Fully private — no text is ever sent to a server
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