Unreal Spent 12.9 CPU-Seconds SHA-1 Hashing Shader Source. The Cache Key Never Needed to Be Secure

Tue, 13 Oct 2026 08:30:00 +0530

A profile of Unreal Editor startup on the Electric Dreams sample project showed FSHA1::Update under “Compile Global Shader Map,” hashing shader source text. Lars Tofus reported 12.90 seconds spent there, summed over five launches with and without the change (ten runs total). With FXxHash64Builder, which Unreal already ships, the same work took 1.59 seconds. He calls that eight times faster.

The ratio is the least interesting part. Two other details decide whether you should copy the change.

Profiling on Kuldeep Pisda

Unreal Spent 12.9 CPU-Seconds SHA-1 Hashing Shader Source. The Cache Key Never Needed to Be Secure