tl;dr: Stockfish 19 delivers up to 44 Elo gain over version 18, winning 3x as many game pairs as it loses. Key changes include a new SFNNv16 NNUE architecture (with pawn-pair features and retirement of the secondary small net), Quantization-Aware Training, and universal binaries that auto-detect CPU features. It also adds native support for RISC-V, LoongArch, WebAssembly, and 1GB Linux huge pages, plus stricter FEN/UCI validation that terminates the process on invalid input.