What it does
Tracy is a PHP debugging bar and error page library that has been shipping since 2012. Drop it into a Laravel, Symfony, Nette, or plain PHP app and you get request timing, SQL queries, dumps, and a useful exception page instead of a blank 500.
It is not a full APM and it is not Xdebug. It is the tool you leave on in local and staging so you can see what the request actually did without attaching a debugger.
Why it still matters
Most PHP stacks already have something like Telescope, Debugbar, or Symfony's profiler. Tracy's niche is being small, framework-agnostic, and honest about what failed. The bluescreen is still one of the clearest PHP exception UIs, and bdump() / Debugger::barDump() are faster to reach for than wrapping every dump in a custom helper.
Stars and forks on GitHub support that it is still maintained and used — not a abandoned 2012 artifact.
Should you install it?
Yes, if you work in PHP without a heavy first-party debug stack already wired in. Prefer your framework's built-in profiler when it is already configured and trusted. Do not enable the full bar in production; use the production error page mode only.
Verdict
A durable utility review, not a hype post. Tracy does one job well: make PHP failures and request guts visible while you build.