The latest articles on DEV Community by Hanné (@hannedev). https://dev.to/hannedev https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.us-east-2.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F4205592%2F3618108b-5a77-45df-b71a-2f12dd09bca9.jpg https://dev.to/hannedev en Hanné Sat, 24 Oct 2026 23:52:29 +0000 https://dev.to/hannedev/why-f-breaks-openapi-rendering-note-names-url-encoding-and-the-clash-between-music-notation-and-3573 https://dev.to/hannedev/why-f-breaks-openapi-rendering-note-names-url-encoding-and-the-clash-between-music-notation-and-3573 <p>I'm building a music theory API. I typed F# as root note into the "tonic" interface, which OpenAPI translated into a URL and I got a subsequent 404. Everything broke. Here's what happened and how I created a work-around.</p> <h2> What # means to a URL </h2> <p>The # character is reserved in URLs to signal a fragment identifier. Everything after the # character is interpreted by the browser as an anchor on the page, not part of the path. So something like <code>/scales/F#/major</code> is parsed as <code>/scales/F with fragment major</code>. The server never even sees the # and we get a 404 error response right away when trying to render in OpenAPI.</p> <h2> What the # symbol means to a musician </h2> <p>The sharp symbol in music applies to a note name to raise it by a semitone. In the context of naming scales, as for the API, the root note is the name given to the scale and so F# must be the root note for a scale beginning on the note F-sharp. This becomes a matching issue in pre-programmed interfaces like OpenAPI interfaces, which weren't designed for music first formats initially but the two now have to "talk to" each other.</p> <h2> The Solutions People have Reached for </h2> <p>URL encoding (F%23), query parameters, string substitution (Fs) are all potential solutions to the issue. Each one works technically, but breaks something musically or semantically, because it's clumsy to annotate to non-technical users, and string substitution like Fs doesn't make sense musically.</p> <h2> The German Naming Solution </h2> <p>German music notation uses the suffix "is" for sharps and "es" for flats i.e. Fis, Cis, Es, but notably B for Bb. Despite the workaround, no special characters are needed. Clean URLs. (Also, it's not a hack; it's a centuries-old naming convention used in some of the greatest musical traditions.) </p> opensource musictheory openapi coding