I have Firefox version 51.0.1 and Firebug version 2.0.18 (though it just says "deactivated"). I have been installing the latest FirePath over and over but I don't see it appearing when I click the Firebug icon.
They both are enabled in my extensions. I saw it a few days ago but I had to reinstall Firefox yesterday for some reason, and both Firebug and FirePath were gone and now giving me problems. Can someone help?
Please see the answer in this question. definitely it will work-
Firebug toolbar button is always shown deactivated since Firefox 51.0.1
Firebug development is discontinued and it does not work anymore once multi-process Firefox is enabled and clicking the Firebug button opens the Firefox DevTools instead. You can read more about this in the related Mozilla Hacks blog post.
This also affects FirePath, because it doesn't work with the Firefox DevTools.
They don't have an exact equivalent to it, but allow you to test XPaths via the $x() command within the command line. Furthermore, there are requests for copying the XPath of an element and for searching for XPaths within the Inspector.
There's also a way to get Firebug and FirePath work again by disabling multi-process Firefox. Though that is only a temporary solution, because multiple processes will be enforced in an upcoming version of Firefox.
What I did was just delete my Firebug and Firepath, download Firebug version 2.0.18 and install Firepath again. It is working fine for me.
The latest Firefox has used DevTool instead of Firebug.
You can reactivate Firebug to rework as the above mentioned links.
In about:config set the preferences browser.tabs.remote.autostart, browser.tabs.remote.autostart.1, and browser.tabs.remote.autostart.2 to false.
I am just sharing what I found while on google. Instead of downgrade anything, you guys can use ChroPath. It is available for both - Chrome as well as Firefox.
chrome plugin : https://chrome.google.com/webstore/detail/chropath/ljngjbnaijcbncmcnjfhigebomdlkcjo?hl=en
firefox plugin : https://addons.mozilla.org/en-US/firefox/addon/chropath-for-firefox/
here is video : https://www.youtube.com/watch?v=HZnMieaLY8c&feature=youtu.be
actual site : https://medium.com/@mailcoolsanjay/chropath-firepath-for-chrome-browser-3130e72b4754
来源：https://stackoverflow.com/questions/41992056/why-doesnt-firepath-work-anymore-since-firefox-51-0-1