Recenlty I have been using the tool Grammarly, both for my own writing and to help students improve their writing. Grammarly checks your spelling and grammar either through their website or within your social media posts if you have installed the Grammarly extenison.
The picture above shows how Grammarly works when you are are writing within the Grammarly website.
The picture below shows how Grammarly works when you have installed the extension. Grammarly will then check your spelling and grammar within Google apps, Facebook, Twitter, WordPress and Linkedin to name a few. Below is an example of Grammarly working with my Gmail.
At the moment I have only used the free version of Grammarly, which has been hugely helpful. However, you can pay for the premium version if you want even more features.
As a teacher this tool is great as I use it to check my own work. However, the main benefit is the way we can encourage our students to use it to improve their writing. Grammarly not only picks up the mistakes, it also tells you why it was a mistake. This turns this tool into something that can enhance student learning, rather than just a spell checker.