instalogin

The extension doesn't require any special permissions. All of the code available at github.
When you click "Fill It", it sends a requests to the server to get a random email, a username, and a password. And then, it fills up the form if it finds one (if it doesn't, you can just copy the email yourself and use it). Only an email is stored in our database.
You don't need to use provided username or password. You can fill those yourself to anything you want.
Emails theoretically can be read by us. Don't use this service for anything super important.
We built this for ourselves first. We use this extensively: when we don't want to reveal our real email, when we just want to check some service fast (and get verified automatically without needing to go to the mailbox), or when we want to create some verified throwaway account (e.g. on reddit).
Have questions, feedback etc.?
Join forum and ask