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Source Maps: the ECMA-426 Format, Hidden Source Maps in Production, Error Tracking and Security

A source map is a JSON file that maps every position in minified code back to the source, standardized as ECMA-426 since December 2024; a hidden source map only drops the sourceMappingURL comment, so anyone can download the file if it is on the server. In Bookstore we decode the mappings field's Base64 VLQ, see ASP.NET Core serving the .map file, keep maps out of the deploy and map a production error back to a TypeScript line with a debug ID.