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SIMON WILLISON · 05 Jul 2026

Building a World Map with only 500 bytes

Iwo Kadziela successfully created a detailed ASCII world map using only 445 bytes of data. By leveraging deflate compression, he condensed the complex character-based image into a tiny file size that fits well within strict memory constraints.

The technical implementation relies on a specific JavaScript approach that uses the fetch function to process a base64-encoded data URI. The code pipes this data through a decompression stream, which reconstructs the original text-based map. Once decompressed, the script injects the resulting ASCII art into an HTML element with a small font size to ensure the entire map displays correctly on the screen.

This project demonstrates how modern web APIs can be used to handle highly compressed data in unconventional ways. By combining data URIs with built-in browser decompression tools, developers can store and render complex visual information with minimal bandwidth and storage requirements. This method highlights the efficiency of using standard web technologies to achieve compact, self-contained graphics.

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