rr by Mozilla
Shares rank 5 of 9 debuggers by recommenders
Mozilla's free time-travel debugger records a program run so bugs can be replayed and inspected, which people say saves hours of debugging.
Mozilla's free time-travel debugger records a program run so bugs can be replayed and inspected, which people say saves hours of debugging.
7 people gave an opinion
- recommend it
- 7
- criticize it
- 0
- approval share
- 100%
Recommended in 4 of 13 months
- November 2025: recommended
- December 2025: recommended
- January 2026: recommended
- February 2026: not recommended
- March 2026: not recommended
- April 2026: not recommended
- May 2026: not recommended
- June 2026: not recommended
- July 2026: recommended
- August 2026: not recommended
- September 2026: not recommended
- October 2026: not recommended
- November 2026: not recommended (month in progress)
Why it doesn’t carry the badge
- 7 people recommend itNeeds 10 or more, not met.
- Nobody criticizes itNeeds 2 to 1 or better, met.
- Recommended in 4 of 13 monthsNeeds 4 or more, met.
The same three rules apply to every product, and the badge can’t be bought. How the badge works
What people say about it
The reasons people give, with the number of comments that give each one. Open a reason to read what they said.
Why people recommend it
Each mark is one comment
Replays bugs for debugging
“Things that took hours or days to debug before take mere minutes once I have an rr recording.”
Comment from 14 Nov 2025 in “V8 Garbage Collector” “If you change the debugger to rr you can even replay.”
Comment from 16 Dec 2025 in “VS Code deactivates IntelliCode in favor of the paid Copilot” “Sounds like you want a time travel debugger, eg. rr.”
Comment from 26 Jan 2026 in “DDD was a great debugger – what would a modern equivalent look like today?” Makes hard bugs quick to fix
“Things that took hours or days to debug before take mere minutes once I have an rr recording.”
Comment from 14 Nov 2025 in “V8 Garbage Collector” “a godsend when it comes to analysing heap corruptions”
Comment from 14 Nov 2025 in “V8 Garbage Collector” Praised as a great tool
“Ah that looks like a great tool, will try to keep it in mind if I run into those kinds of issues again.”
Comment from 16 Nov 2025 in “V8 Garbage Collector” “I was a huge fan of Mozilla's rr [0] in undergrad.”
Comment from 5 Jul 2026 in “The Log Is the Agent”
Other debuggers people recommend
The four most recommended other debuggers, with the same counts for each, so you can compare like for like. The tick on each bar marks the 2 to 1 line the badge needs.
| Product | Recommend | Criticize | Approval | Months | Owned | Badge |
|---|---|---|---|---|---|---|
| GDB (GNU Debugger) | 29 | 16 | 64% | 10 | — | — |
| WinDbg | 14 | 3 | 82% | 7 | — | Approved |
| HyperProbe | 12 | 1 | 92% | 1 | — | — |
| RenderDoc | 10 | 1 | 91% | 4 | — | Approved |
| rr by MozillaThis page | 7 | 0 | 100% | 4 | — | — |
What people said
All 7 comments that mention it, newest first. Each links to the original comment.
“I was a huge fan of Mozilla's rr [0] in undergrad.”
“it never worked on codebases that I worked on”
“Sounds like you want a time travel debugger, eg. rr.”
“If you change the debugger to rr you can even replay.”
“Ah that looks like a great tool, will try to keep it in mind if I run into those kinds of issues again.”
“Things that took hours or days to debug before take mere minutes once I have an rr recording.”
“a godsend when it comes to analysing heap corruptions”
Counts come from 1,795,640 Hacker News comments, November 2025 to November 2026. How we count. Report a mistake.