When Your Maps Disappear Overnight – A PMTiles Horror Story

Thanks to Mario Ame Everything was working fine. I had just finished building the Grow Your Own allotments map, deployed it to the live server, and was feeling pretty pleased with myself. A few days later a friend messaged me that the map had stopped working. No regions, just a blank basemap. Checked the console and got this: “Server returned no content-length header or content-length exceeding request. Check that your storage backend supports HTTP Byte Serving.” Not the most helpful error message if you don’t know what you’re looking at. Fortunately Claude was able to work out what was happening and suggest a solution. PMTiles is a clever format for serving vector map tiles — instead of thousands of individual tile files, everything is packed into a single binary file and the browser requests just the chunks it needs using something called HTTP byte-range requests. For this to work, the server has to serve the file uncompressed and report its exact size. The problem was that…