This tool’s been useful to me – I like it!
Note: This is not an endorsement.
Due to recent issues with Firefox, I’ve discontinued use of this extension as part of my troubleshooting. There’s several known issues and though it is a Firefox-recommended extension, I’m not sure I can recommend it.
I’ve removed the extension. It appears (to me anyway) to have been the cause of the Firefox issues. I cannot recommend using the extension – sorry.