API error responses
Every 4xx from the UseQR API is an RFC 9457 application/problem+json document with one extra field: fix, a corrected call you can paste straight back into your terminal or hand to an agent. There are no API keys, so there are no auth errors — only input problems, and each one teaches its own solution.
$ curl "https://useqr.app/api/v1/qr?data=hello&format=nope"
{
"type": "https://useqr.app/errors",
"title": "Invalid parameter",
"status": 400,
"detail": "format \"nope\" is not supported",
"field": "format",
"fix": "use format=png, format=svg, format=svg-tiny (SVG Tiny 1.2 for Illustrator and cutters), format=json (the module matrix), or format=base64"
}- title — the category of problem.
- detail — what went wrong, quoting your input.
- field — which parameter to change.
- fix — a working replacement call.
Batch calls never fail as a whole because one item is wrong: request-level problems (bad JSON, too many items) come back as problem+json, while per-item problems come back inside results[] with their own error and fix.