I cut GTA Online loading times by 70% (2021)
A developer investigated why Grand Theft Auto Online took up to six minutes to load, discovered a single-threaded CPU bottleneck caused by a 10MB JSON file being parsed inefficiently with O(n²) complexity, and published a fix that reduced loading times by 70% for many players.
Background
- Grand Theft Auto Online (GTA Online) is the multiplayer component of Rockstar Games' blockbuster title GTA V (2013). Loading into the online world was notoriously slow — often taking 5–10 minutes even on fast PCs.
- In February 2021, independent developer "t0st" reverse-engineered the game's loading process and discovered a single function with a 1.9GB memory allocation that was running on a single CPU thread, creating a massive bottleneck.
- The fix? A one-line code change that swapped an inefficient `sscanf` call for a custom JSON parser, cutting load times by ~70% (from ~6 minutes to under 2).
- Rockstar had not publicly patched the issue for years. After t0st's blog post went viral, Rockstar acknowledged the analysis and released an official fix in a subsequent title update.
- The story became a celebrated case of a modder outperforming a multi-billion-dollar studio's QA/engineering, highlighting how legacy code and single-threaded bottlenecks can degrade modern user experience.