Firefox Replay records your application, so you can track bugs down faster and understand your code better.
We designed the timeline to make debugging fast and intuitive. Scan through your code execution with one glance. See a preview of the DOM by hovering on the timeline. Just like a video.
Replay's timeline also marks other points of interest — like exceptions, events and network requests — in real time. Once you decide where to take a closer look, Replay makes pausing and inspecting any marker a breeze.
Once you're paused, you have the entire suite of debugger tools at your disposal. For more precise navigation, use the command bar to explore your code. Did we mention you can step backwards?
Replay was made for collaboration, so it's possible to save and load your recordings. Stash a recording and pick up where you left later, or share the recording with somebody else.
Download Firefox Nightly for macOS
Open DevTools, click on settings and click on "Enable Replay"
Click the Record button in DevTools