Tinker Tester Developer Spy by Thomas Wisniewski

Have you ever wanted to be able to create specialized breakpoints while debugging a website, on desktop or Android Firefox? Now you can!

Log a stack trace whenever pesky scripts modify a specific element's style properties to certain values.

Start the debugger to get dirt on where those stubborn DOM event listeners are attached to a set of elements, or when they fire.

Prevent document.write from having any effect to spot those tough-to-find issues where ads break your page loads.

Pin-point which of the many places in the scripts where navigator.userAgent or video.src or scrolling properties are the ones actually causing a problem, without the grey hair that results in doing so manually with global search.

But wait, there's more!

Maybe you're more interested in re-mapping a specific network request to a local file, where you can more easily de-minify and test it.

Or maybe you'd like to confirm whether specific HTTP headers are causing an issue by over-riding them, or you feeling like spoofing your geolocation or language to see how a site changes?

There is a whole suite of hooks and tools available in Tinker Tester Developer Spy, the tool being used to help aid webcompat.com site diagnoses!

(Disclaimers: Recent studies show that direct contact with Tinker Tester Developer Spy may cause giddyness. User interface has been known to cause fits of confusion; please consult the readme at the add-on homepage for assistance. Readme has also been known to cause fits of confusion; please consult the author as necessary.)