This section explains the requirements for assigning cache tags.

To ensure that your content is purged successfully, follow these requirements.

  • A single tag cannot exceed 128 characters. If you enter a tag exceeding 128 characters, the specific content associated with that tag will not be purged when the purge is submitted. Note that you will not see an error.
  • Multiple tags in the Edge-Cache-Tag header must be delimited by a comma (,). For example, Edge-Cache-Tag: casual, knits, fall-sale.
  • The maximum number of tags per object is 128. If you exceed this, the additional tags will be ignored. Note that the default Akamai max reply headers size is 8192 bytes.
  • Tag format is derived from the format of a token specified in RFC 7230, Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing.
    The following table lists allowed and disallowed cache tag characters.
    Allowed Disallowed
    Alphanumeric Angle brackets (< >)
    Ampersand (&) Asterisk (*)
    Apostrophe (’) At sign (@)
    Circumflex (^) Backslash (\)
    Dash (-) Braces ({ })
    Dollar sign ($) Colon (:)
    Exclamation mark (!) Comma (,)
    Grave accent (`) Double quote (“)
    Hash sign (#) Equal sign (=)
    Percent sign (%) Open/closed parenthesis (( ))
    Period (.) Question mark (?)
    Plus (+) Semicolon (;)
    Tilde (~) Slash (/)
    Underline (_) Space ( )
    Vertical bar (|) Square brackets ([ ])