NOTE: As of Xcode 26, content-based caching is built in to LLVM. WebKit enables it via the COMPILATION_CACHE_ENABLE_CACHING build setting and emits cache hit metrics in build logs. Extra diagnostics are available with COMPILATION_CACHE_ENABLE_DIAGNOSTIC_REMARKS=YES.

Prerequisites

• Xcode < 26 (or opt out of the default compilation caching behavior).
• ccache(1) installed in /usr/local/bin

Configuring ccache

The maximum cache size is 5GB by default, but a WebKit Debug build can require 20GB or more:

• ccache --max-size=20G

Building with ccache

• make ARGS="WK_USE_CCACHE=YES"
• build-webkit WK_USE_CCACHE=YES
• Build in the Xcode UI by adding WK_USE_CCACHE = YES; to Tools/ccache/ccache.xcconfig (FIXME: this dirties the working directory).

Viewing cache statistics

• ccache -s