X-Cache-Group
The HTTP X-Cache-Group unofficial response header identifies which cache group a caching proxy assigned to a response. WP Engine's page cache is the primary sender, using the header to expose its device-detection groups.
Usage
WP Engine's Varnish-based page cache stores separate cached copies of each page per device class. The cache inspects the User-Agent request header, assigns the request to a group, and serves the cached variant belonging to the group. The X-Cache-Group header exposes the assignment, making the classification visible for debugging.
Splitting the cache by device class keeps mobile-specific markup from being served to desktop visitors and vice versa. Each group maintains its own cached copy, so a purge or a cache miss in one group leaves the others untouched.
This header is primarily a diagnostic tool. Developers and operators verify device detection is routing responses into the expected group. When a response ends up in the wrong group, the header makes the misclassification visible without needing to inspect the platform's internal configuration.
Values
Values are labels defined by the caching platform. WP Engine's
device-detection groups are the dominant set observed in the
wild, with normal accounting for the vast majority of
responses.
normal
The normal value indicates a desktop request served from the
default cache group. This is the most common value by a wide
margin.
iphone
The iphone value covers all mobile user agents, and the
response came from the mobile cache group. The group name is
historical rather than iPhone-specific.
ipad
The ipad value indicates the request was classified as
coming from an iPad and served from the iPad cache group.
Crawler grouping
Crawlers do not receive a dedicated group in observed
traffic. Live probes show Googlebot Smartphone served
the iphone group and desktop Googlebot the normal
group, so bot handling depends on configuration rather
than a fixed value.
bot-mobile
The bot-mobile value indicates a crawler presenting a
mobile User-Agent served from a dedicated mobile-bot
group. Live probes show Googlebot Smartphone receiving
the plain iphone group instead, so the bot grouping
depends on configuration.
mobile-maybe
The mobile-maybe value indicates the User-Agent matched a
generic mobile pattern without mapping to a specific device
group.
Crawl data shows normal on nearly every observation
with iphone as the runner-up. Other platforms define
their own site-specific labels for their cache groups.
Example
A desktop page served from WP Engine's page cache carries the
normal group. Operators confirm the default cache variant
was used.
X-Cache-Group: normal
A request from an iPhone is routed to the device-specific cache group, confirming the platform stores and serves a separate cached copy for iPhone visitors.
X-Cache-Group: iphone
X-Cache: HIT