Doesn't work anymore, it lets you view but not edit anything. Hasn't been updated in 3 years either. Whether its the developer's fault, or Mozilla's fault, this app no longer functions for its intended purpose.

good

Request cannot be edited? -I've found out that due to limitations in newer versions of Firefox it is not possible to edit data, so the developers are not to blame for this.

You can't tamper (change or add new) data with this. You can capture request and visually check what is inside.

Ends up opening a bunch of useless popups that you don't have time to view before more are opened.

The name of this extension is a complete misnomer, one cannot actually tamper with the posted data, and since it claims to do what the old Tamper Data extension did, it seems intentionally misleading and borderline fraudulent. Do the right thing and change the name.