URL Params is a really useful extension for working with long URLs and POSTDATA. It will split query string parameters into separate fields for each parameter which you can edit and resubmit as you see fit. It hasn’t been updated since the Firefox 3.x days, but still mostly works.
The main known issues are:
- you may need to close/reopen the dialog when you navigate between URLs / tabs
- it can’t handle multipart forms (e.g. those with a file upload field)
- Firefox refuses to install it, because its declared maximum version is too low
I’ve taken the latest release and increased the declared maximum version, so if you want to use it on a recent version of Firefox then use the link below.