language-agnostic - "image/png"和 "image/x-png"和有什么区别？

Question

“image/png”和“image/x-png”有什么区别？

Answer 1

x- 前缀用于非标准 MIME 类型(即未向 IANA 注册)。因此，我假设在 MIME 类型标准化之前 image/x-png 应该是 PNG。

6.3. New Content-Transfer-Encodings

Implementors may, if necessary, define private Content-Transfer-Encoding values, but must use an x-token, which is a name prefixed by “X-”, to indicate its non-standard status, e. g., “Content-Transfer-Encoding: x-my-new-encoding”. Additional standardized Content-Transfer-Encoding values must be specified by a standards-track RFC.The requirements such specifications must meet are given in RFC 2048.As such, all content-transfer-encoding namespace except thatbeginning with “X-” is explicitly reserved to the IETF for futureuse.

—RFC 2045 — Multipurpose Internet Mail Extensions, Section 6.3

这也记录在 PNG 规范中。请参阅FalseVinylShrub's answer .