Autocorrect is currently available in the Grammarly browser extension.
You can switch autocorrect on or off by clicking the Grammarly button in your browser’s toolbar and toggling the switch next to Correct spelling automatically:
Once Grammarly has corrected a certain word, a gray dotted line appears under it. To see what changed, hover over the underlined word in question:
Note: If you use Grammarly on a mobile device, the autocorrect feature is also available in the Grammarly Keyboard for iOS and Android.