Building a World Map with only 500 bytes

Simon Willison highlights a clever technique by Iwo Kadziela (with assistance from Codex) that generates a credible ASCII world map from just 445 bytes of compressed data. The core insight is using deflate compression to shrink the map data, then decompressing it in the browser via the `DecompressionStream` API. A particularly neat aspect is the use of `fetch()` with a data: URI—a pattern that may be unfamiliar to many developers—to feed the compressed base64 payload directly into the decompression pipeline without an external server request. The result is rendered in a `<pre>` tag with a tiny font size. For developers building AI workflows, this demo illustrates how browser-native compression APIs can dramatically reduce payload sizes for static data, which is useful for shipping small models or lookup tables. It also showcases a clean, modern JavaScript pattern for inline data processing that avoids third-party libraries. The combination of Codex assistance hints at how AI can help prototype such low-level optimizations.