X-Akamai-Transformed
When Akamai's edge applies a content transformation, such as script injection for monitoring or minification, the X-Akamai-Transformed unofficial response header records what happened.
Usage
When Akamai's CDN processes a response, edge servers apply content transformations. In crawl data the header rides on HTML and robots.txt responses rather than images, pointing at edge script injection and minification as the operative transformations. The X-Akamai-Transformed header records what was applied, giving operators visibility into how the edge modified the original response.
Akamai publishes no documentation for the value format, so the field meanings are known only from observation. Operators use the header's presence as a signal that edge processing touched the response, and compare transformed versus original response sizes for performance tuning where a size field is recognizable.
Values
Transformation string
The value is a space-separated string, typically with four
fields. Akamai does not document the field semantics, and
observed values in the wild show more variation than any
single decoding scheme accounts for, including forms like
9 - 0 pmb=mNONE,1mRUM,3. A few patterns are consistent
across observations. The second field, when numeric,
drifts slightly between fetches of the same page while
the content length holds constant, so the field tracks
something other than response size. - acts as a
placeholder in several positions. Values containing
pmb=mRUM appear on HTML pages from sites running Akamai's
mPulse real user monitoring, consistent with edge script
injection rather than image transformation. The remaining
fields stay opaque without an Akamai statement on their
meaning.
Example
A response from a website served through Akamai's edge
carries a four-field value. The 42534 field is not a
byte count of the response, and the pmb=mRUM marker matches
sites running mPulse monitoring. The other fields are
undocumented.
X-Akamai-Transformed: 9 42534 0 pmb=mRUM,2
A different response replaces the size position with a dash placeholder while keeping the same overall shape.
X-Akamai-Transformed: 9 - 0 pmb=mRUM,3
A minimal value appears on other responses, with every field zeroed or replaced by a placeholder. The exact condition producing this form is undocumented.
X-Akamai-Transformed: 0 - 0 -