Syntax for ETag?

Question

Redbot reports that my webpage has invalid header:

The ETag header\'s syntax isn\'t valid.

My headers are set to:

Answer 1

Try ETag: "4ae413bd". The value of an ETag must follow the ABNF form:

  entity-tag = [ weak ] opaque-tag
  weak       = "W/"
  opaque-tag = quoted-string

  quoted-string  = ( <"> *(qdtext | quoted-pair ) <"> )
  qdtext         = >
  quoted-pair    = "\" CHAR
  CHAR           = 
  TEXT           = 
  OCTET          = 
  LWS            = [CRLF] 1*( SP | HT )
  CTL            = 
  CRLF           = CR LF
  CR             = 
  LF             = 
  SP             = 
  HT             = 

, which is basically ([wW]/)?"([^"]|\\")*" in regular regex.

Note that both "\" and "/" are valid values for etags.

References: section-14.19, section-3.11, section-2.2.