This article discusses the implementation of diff algorithms in Ably's distributed pub/sub messaging platform. It provides a detailed overview of diff algorithms, their purpose and usage, three generations of diff algorithms, current delta generation algorithms, delta file formats, testing open-vcdiff and xdelta, and finally, how these concepts were applied at Ably. The article also includes a comparison between the Google Open VCDiff and XDelta algorithms in terms of time complexity and performance.