# rr by Mozilla

7 Hacker News commenters recommended rr by Mozilla and 0 criticized it, November 2025 to November 2026. It was recommended in 4 of 13 months.

**Verdict:** Mozilla's free time-travel debugger records a program run so bugs can be replayed and inspected, which people say saves hours of debugging.

## Why people recommend it

- Replays bugs for debugging (3 comments): "Things that took hours or days to debug before take mere minutes once I have an rr recording." ([source](https://news.ycombinator.com/item?id=45928722)) "If you change the debugger to rr you can even replay." ([source](https://news.ycombinator.com/item?id=46289947)) "Sounds like you want a time travel debugger, eg. rr." ([source](https://news.ycombinator.com/item?id=46762839))
- Makes hard bugs quick to fix (2 comments): "Things that took hours or days to debug before take mere minutes once I have an rr recording." ([source](https://news.ycombinator.com/item?id=45928722)) "a godsend when it comes to analysing heap corruptions" ([source](https://news.ycombinator.com/item?id=45926319))
- Praised as a great tool (2 comments): "Ah that looks like a great tool, will try to keep it in mind if I run into those kinds of issues again." ([source](https://news.ycombinator.com/item?id=45944195)) "I was a huge fan of Mozilla's rr [0] in undergrad." ([source](https://news.ycombinator.com/item?id=48796030))

## Alternatives hackers recommend

- [GDB (GNU Debugger)](https://hackerapproved.com/p/gdb.md): 29 recommend
- [WinDbg](https://hackerapproved.com/p/windbg.md): 14 recommend
- [HyperProbe](https://hackerapproved.com/p/hyperprobe.md): 12 recommend
- [RenderDoc](https://hackerapproved.com/p/renderdoc.md): 10 recommend
- [RAD Debugger](https://hackerapproved.com/p/rad-debugger.md): 7 recommend

## Cite as

Hacker Approved, "rr by Mozilla", https://hackerapproved.com/p/rr/ (counts from 1,795,640 Hacker News comments, November 2025 to November 2026).