214 Transformation Applied

Description
The HTTP 214 Transformation Applied is an unofficial status code used in combination
with the Warning HTTP header and included with HTTP response messages to indicate
that a transformation has been applied to the representation.
This status code and Warning header MUST be added by a proxy if it applies any
transformation to the representation, such as changing the content-coding,
media-type, or modifying the representation data, unless the Warning header
already appears in the response.
See Also
Source: https://datatracker.ietf.org/doc/html/rfc7234#section-5.5.6