Tripping over English comma rules can muddy your message, but online comma placement checker tools can help you write clear and error-free prose. 

Misplaced commas can cost you anything from intense embarrassment to millions of dollars. That’s no exaggeration. A company in Portland, Maine once had to pay $5 million in penalties and court fees because they left one little comma out of their employment contracts.

Fortunately, you can avoid comma errors if you know a few simple rules and use a reliable punctuation and comma placement checker on all your writing projects.

Each of the following online punctuation and grammar checkers has strengths and weaknesses. They will all help you fix comma errors, grammatical errors, spelling mistakes and sentence structure. Most of them have a free version, and options to pay for premium features geared toward professional writers.

Which artificial intelligence proofreader tool is best for you? 

Grammarly is a great, full-featured comma error checker, spell checker, and grammar checker that will help you nix spelling errors, punctuation mistakes and make suggestions to avoid grammar errors. Its Chrome extension is free and helps you stick to grammar rules. Its paid platform also catches plagiarism gaffes. 

Of all the tools we tried, Grammarly caught the most errant and missing commas/

Read our Grammarly review

This robust English grammar, style, spelling, and punctuation checker integrates with Microsoft Word, Outlook, WordPress, Gmail, Google Docs and other writing tools geared toward professional writers. You can use the basic sentence checker features for free, but they include more features if you want to pay for them. 

ProWritingAid caught some errant commas but not as many as Grammarly. Read our ProWritingAid review

Ginger helps you proofread fast for grammar, spelling, and punctuation errors with its standard proofreading tools. In addition to helping you hone your writing skills, it has a translator with more than 50 language options. It doesn't have a plagiarism checker, however. Ginger lacks the accuracy of ProWritingAid and Grammarly.

Read our Grammarly Ginger comparison to find out why

For $5.00 a month, Whitesmoke is an affordable tool will help you eliminate common comma splice errors and many less-common punctuation mistakes, including semicolon use. However, the user interface isn't as polished as Grammarly. And it lacks many reports present in ProWritingAid. We tried Whitesmoke for a few weeks before going back to Grammarly and ProWritingAid, due to ease of use.

PaperRater is free and premium web-based spelling, typo, apostrophe and grammar checking tool. It uses artificial intelligence to help you root out comma errors. It also checks for plagiarism and gives your writing a readability score with ideas of how to improve. You can check five pages for free via the online submission form. It's powered by Ginger so expect similar accuracy. In our tests, PaperRater missed some issues that Grammarly caught. However, it's free.

Not only does Language Tool do a great job of checking grammar and punctuation in English, it does the same for several other languages. This open-source punctuation corrector is compatible with Microsoft Word, Chrome, Google Docs, Firefox and LibreOffice. It's faster than PaperRate and flagged up some missing commas.

Writer.com is beyond just a great comma splice fixer. Designed for professional writers, it uses artificial intelligence and natural language algorithms to root out punctuation errors, particularly comma placement errors.

It also evaluates writing style, tone, readability, brand voice, and terminology geared for your audience. It's comparable to Grammarly, except for business writers.

What are the Rules for Comma Placement?

Of course, it’s wonderful to have all of these punctuation, spelling, grammar and comma placement checkers available in various formats. You’re sure to find one that fits your needs as a blogger, email marketer, web designer, student, professor, teacher or anyone else who needs to write clearly.

However, nothing can replace a basic, personal knowledge of comma usage rules. 

Don’t Use Commas with “That”

Avoid using a comma before “that” in a restrictive clause. Using “that” tells the reader that the information connected to the first clause is essential. 

• Wrong: I dislike salads, that contain arugula. 
• Right: I dislike salads that contain arugula. 

You should, however, use commas before “which” because they add interesting, but non-essential information to the sentence. These clauses often act like parenthetical phrases, so you will want to add a comma after the clause as well, as shown below: 

• Wrong: The boys’ sweater which his brother gave him scratched his neck. 
• Right: The boy’s sweater, which his brother gave him, scratched his neck.

Do Use Commas Between Two Independent Clauses Joined by a Coordinating Conjunction

First, remember that the coordinating conjunctions are “FANBOYS” (for, and, nor, but, or, yet, so). Coordinating conjunctions can join two independent clauses that could be their own sentences if you separate them with a period. Here are some examples: 

• Wrong: I love bread but I have a gluten allergy.  
• Right: I love bread, but I have a gluten allergy.
• Wrong: It was snowing outside so I put on my boots.
• Right: It was snowing outside, so I put on my boots. 

Don’t Use Commas Before Verbs in Relative Clauses 

Always ask yourself if the information that you’re adding in a clause is essential to the meaning. In the case below, the comma breaks up the essential connection between “is” and the best thing. So you would leave out the comma here: 

• Wrong: One of the best things about using a grammar checker, is getting an error-free blog. 
• Right: One of the best things about using a grammar checker is getting an error-free blog. 

Avoiding the Comma Splice 

Some sentences should really be split into two sentences to avoid dreaded comma splice errors. If you have two independent clauses, but you don’t have a coordinating conjunction to connect them, just use a period: 

• Wrong: I forgot to use an oven mitt, I burned myself
• Right: I forgot to use an oven mitt. I burned myself
• Also Right: I forgot to use an oven mitt, so I burned myself. 

Commas and Dependent Clauses

If a dependent clause (one that cannot be its own sentence) comes before an independent clause in a complex sentence, you need a comma as shown here: 

• Wrong: After we ate dinner at the restaurant we went for a walk along the river. 
• Right: After we ate dinner at the restaurant, we went for a walk along the river. 

On the other hand, if you put the dependent clause in the second position after the independent clause, you can drop the comma like this: 

• Wrong: We went for a walk along the river, after we ate dinner at the restaurant. 
• Right: We went for a walk along the river after we ate dinner at the restaurant. 

Why You Can Trust Us

I’ve written and published dozens of articles for newspapers, magazines and online publications including, Forbes and Lifehacker. I'm also a best-selling non-fiction author, a trained journalist and a copywriter.

Software like the options here forms a key part of my writing workflow for non-fiction. I use these types of software regularly to improve my work and also to check work by freelance writers who publish content on this site.

Our Testing Criteria

We regularly update this roundup of comma checkers as the product evolve. We test new features by checking articles, book chapters and blog posts for grammatical mistakes and other issues. These articles and other writing samples range from several hundred to several thousand words in length. Typically, we test them using the web, desktop and browser apps and plugins.

The Final Word on Comma Placement Checkers

Even experienced writers need all the help they can get to fix comma errors that could ruin the meaning of sentences. For example, consider how the comma (or lack thereof) completely alters the sentence below: 

• Let’s eat, Jenny. 

Or…

• Let’s eat Jenny. 

Commas save lives! If you aren’t sure if your comma placement is correct, it behoves you to avail yourself of at least one comma usage checker mentioned here. Some of them excel more as grammar checkers and punctuation checkers, while others also scan for plagiarism and language usage.

At the very least, get the free version of Grammarly and watch how much it helps you improve your comma usage and clarifies your writing. If you have a bigger budget, use either ProWritingAid or Grammarly Premium.

Want more? Check out our guide about when to use comma with examples.

FAQs About Comma Placement Checkers