How data is represented in transit.
WHAT A CONTENT TYPE DECLARES
The format of the body.
WHY IT MATTERS
The receiver parses according to it, and a mismatch produces confusing errors.
WHAT TO SEND
The header matching what you actually send.
WHAT THE COMMON TYPES ARE
Structured text, for most interfaces Form encoding, for simple submissions Multipart, for file uploads Plain text Binary formats, in performance-sensitive cases
WHAT ACCEPT HEADERS DO
Declare what the caller can handle.
WHAT CONTENT NEGOTIATION IS
The server choosing a format based on that.
WHY IT IS RARELY WORTH IT
Supporting several formats multiplies testing for little benefit.
WHAT TO DO INSTEAD
Support one, and document it.
WHAT TO BE CAREFUL WITH IN SERIALISATION
Numbers too large for the receiver's type Decimal precision lost in conversion Dates serialised inconsistently Character encoding
WHY LARGE NUMBERS SPECIFICALLY
Identifiers beyond a certain size lose precision in some languages, silently.
WHAT TO DO ABOUT IT
Send large identifiers as strings.
WHAT TO SPECIFY
The character encoding, explicitly.
WHAT TO TEST
Round-tripping awkward values: accented characters, very large numbers, empty values.
