HTTP Accept Header Content Negotiation Matcher

Content negotiation is the mechanism through which client and server settle on the response format. The client sends what it accepts in Accept, with preferences; the server holds a list of what it can produce; and something has to cross the two. When the outcome is not what you expected, the response arrives in the wrong format or as a 406, and the cause is rarely obvious in the log.

Enter the incoming Accept header and the list of formats your application offers, and the page shows which would win and with what quality factor. The criterion is the highest q among the types present on both sides, with the general wildcard coming into play when the client declares it accepts anything. When nothing matches, the result says so explicitly, which is the 406 scenario.

Worth knowing the limit of this comparison: it handles exact types and the full wildcard, but not the subtype wildcard, of the type-followed-by-asterisk kind. The specification requires giving precedence to the more specific — an exact type beats a subtype wildcard, which beats the general wildcard — and real servers implement that ladder. To check how yours behaves, test with curl sending different headers.