Apple rewrites TrueType font hinting interpreter in Swift, improving memory safety and performance across its platforms

Apple says it migrated its security-critical TrueType hinting interpreter from C to Swift for its Fall 2025 releases. The rewrite aims to reduce risks from processing untrusted font data and runs 13% faster on average than the previous C implementation, with source code now published.

The move reflects a broader industry shift toward memory-safe languages for legacy attack surfaces like parsers, codecs, and interpreters. Apple’s performance gains also strengthen the case that safer rewrites can improve, not just preserve, low-level system performance.

Swift at Apple: Migrating the TrueType hinting interpreter