Grammarly is by and far the most popular grammar checker you can use. Not only does it look for grammatical errors, but it checks your spelling and aims to improve readability too. It can cut down on wordiness, passive voice, and repetitious use of words. It can also make suggestions to better align your writing with your audience and overall intent. Grammarly has also added AI features that can help generate text, rewrite passages, and more.
I use a grammar checker which probably corrects every single sentence I type. One should just bear in mind though that a grammar (or spell) checker needs access to every page you visit/type in order to make any suggestions or corrections.
See 6 Best Grammarly Alternatives to Check Grammar and Readability
Writing is not that easy, but these Grammarly alternatives can help.