Browsers now come with all manner of developer tools for debugging websites, inspecting code and even making live changes. HTML, CSS and XML are easily interpreted and presented in human-readable form, but just-as-important formats such as JSON still come out as a wall of monospaced text. Soon that won't be the case for Firefox.
Although Firefox has had a JSON viewer for a while, it was only switched on by default in the developer build and required a flag tweak to work elsewhere.
Mozilla recently made the decision to enable it in all channels, so users will have access to it immediately -- no extra work required.
Even so, it'll be a few months before we see the change in the wild -- for the stable channel, it's slated for Firefox 53, according to gHacks' Martin Brinkmann.
Nice to have another tool in the arsenal, especially for something as prolific as JSON.
Bug 1243951 -- Enable JSON Viewer for all channels [Bugzilla, via gHacks]