Here you can find a nice comma checker tool
The main idea of the comma checker tool is to help people to improve their grammar knowledge. Besides, such tools help people, who newly started to learn a foreign language and don’t really know much about the structures of the sentence at all. So, to be sure that they have everything written correctly, this program or plugin of the program will scan the text and inform you about is or isn’t there any mistakes. Grammar is a big system, that includes other mini systems, such as punctuation. This is exactly where commas and their “friends” live.
One more benefit of this program is that you can see your result right away.