Chrome’s switch to OS-native Math.tanh exposes a subtle JavaScript fingerprinting signal across Linux, macOS, and Windows

The article says Chromium 148 changed V8’s Math.tanh implementation from a bundled fdlibm version to the operating system’s native math library. Because Linux, macOS, and Windows return slightly different last-bit results for some inputs, sites can use Math.tanh to infer a user’s underlying OS and detect mismatches with the claimed User-Agent.

This highlights how even tiny floating-point differences can become fingerprinting signals when browser engines delegate behavior to platform libraries. It may pressure browser vendors to restore deterministic cross-platform math behavior or add mitigations as anti-fingerprinting defenses expand beyond obvious surfaces like canvas and fonts.