I hope the developer would come back to this project and add the functions many have suggested. Being able to change the colour, position, trigger key combination, height & width of the ruler, and add multiple rulers to the screen or activate different rulers on different websites to adapt to their unique layouts would be a huge boon I'm willing to pay big money for. There's literally no other add-on for Firefox or any browser or Windows system-wide.

This tool is pretty helpful. Would love to have the ability to change the keycommand though. Makes it a bit of a pain on macos with that pesky cntrl-click

The concept is perfect for what I need, but it would be more helpful for me to have the option to change the height of the box and the color. Is there a way to do this?

10 years ago I had a bookmarklet for that purpose and I missed it so much when it stopped working. Thanks for this extension. Please make it compatible with the reader mode and it will just be perfect.