Free Run-on Sentence Checker

Check and correct run-on sentences in your blog posts, academic papers, and essays.

→ Completely free to use
→ Quickly checks and corrects sentences
→ Advanced AI Technology for enhanced accuracy
→ Make your sentences easy to read
→ Access it from any device


Tired of grappling with those never-ending sentences that wreck your writing flow and leave your readers confused? We get it.
Sentence Ckeckup’s run-on sentence checker will help you make complex sentences clearer and easy to read.

How can run-on sentences ruin your writing?

A run-on sentence combines two or more independent clauses in one sentence without proper punctuation or conjunctions. It thus results in sentences that are too long and often confusing and hard to read. Think of them as sentences that are cramming multiple thoughts or ideas together without giving the reader a clear break.

How can a run-on sentence checker help?

A run-on sentence checker is like having a skilled editor by your side. Our run-on sentence checker improves your writing by making those cumbersome sentences more accurate, clear, and readable.
Simply copy and paste the text, and the tool will identify and correct run-on sentences.

Refine and Correct Your Sentence

Corrects Comma Splices

The checker identifies and fixes comma splices. Change “He loves cooking, he often experiments with new recipes” to the grammatically correct “He loves cooking; he often experiments with new recipes.” No more pesky comma splices!

Detects and Corrects Punctuation

The checker suggests where to add necessary punctuation like commas, semicolons, or periods.

Adds Conjunctions 

It may recommend adding conjunctions (like ‘and’, ‘but’, ‘although’, etc) to connect clauses properly. For example, in “I was tired I still finished the project,” the tool might suggest “I was tired, but I still finished the project.”

Splitting Sentences

The tool suggests splitting a run-on sentence into two or more separate sentences. From “She enjoys painting her artwork is quite impressive,” it would make two sentences: “She enjoys painting. Her artwork is quite impressive.”

Write with More Confidence 

Don’t just take our word for it. Over 20,000 students, writers, and professionals like you have improved their writing with our Run-On Sentence Checker.

Alexandra Jenkins

“As a freelance writer, I’m constantly juggling multiple projects and deadlines. This sentence checker helps me catch- those lengthy sentences that I sometimes miss in my rush. It’s incredibly user-friendly and efficient.”

Emily Torres

“I never realized how much my run-on sentences were affecting the quality of my academic papers until I started using this checker. ‘[[This tool is absolutely invaluable for any student.”

Jordan Kim

“As a non-native English speaker, I often struggle with sentence structure. The sentence checker helps me understand where my sentences are too long. I highly recommend it to anyone looking to polish their writing skills.”

Correct Your Run-on Sentences Now – it’s free.

Don’t let long sentences slow you down. 

Try Now!

How Sentence Checkup’s Sentence Checker Works

This sentence checking tool uses advanced AI to check for punctuation, grammar, and spelling errors and improve your sentences. You can check run-on sentences in just three steps: 

Step One

Copy and paste the text you want to check into our tool. 

Step Two

Click the “Check” button, and it will highlight all mistakes.

Step Three

You can correct them one by one by hovering over to the highlighted text, or hit the “Correct” button to correct all errors in just one click. 

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