X-Fstrz HTTP header

Introduction

The header X-Fstrz is added by Fasterize to HTTP responses. It indicates what the optimization engine has done (or not done) for a given request. This header contains a series of flags separated by commas.

Here is the complete list of these flags and their meanings.

List of possible header values X-Fstrz

• p : proxified request/response
• w,p : optimization in progress
• f,p : front/forward, proxy
• Z,p : page cannot be optimized (will never be optimized, 404, 301, 302, POST, etc.). The reason is given by another flag:
  • m : method (HEAD, PROPFIND, OPTIONS, PUT, DELETE, etc.)
  • ecc : exclusion via client configuration
  • EEC : exclusion via engine configuration
  • stc : status code of origin different from 200
  • ab : exclusion by A/B testing
  • zc : empty content

When no additional flags are present, optimizations are simply disabled.

• h : content that is not HTML (JSON sent with a content-type text/html, for example)
• o : optimized
• !o : not optimized
• c hidden
• !c : not hidden
• o,c : optimized, hidden
• w,c : response being optimized but served cached
• dc,o : optimized, dynamic cache (internal engine operation)
• sc : the page is hidden via SmartCache (Cache + Ajax)
• clc : the page is hidden via the Cookie Less Cache
• pl : preload links have been inserted
• ed : engine disabled
• v : virtual object (result of concatenation or outlining)
• vf : reconstructed virtual object
• t : timeout, optimization took too long, the returned page is not optimized
• tb : too big, the resource is too large to be optimized
• e : error, optimization failed, the returned page is not optimized
• b : blocked, the IP address is blocked
• P.S. : persistent storage
• pp : partial page
• pc : probabilistic cancel
• that : canceled
• wr : waiting room
• uc : User Canceled, the request was canceled by the user
• cbo : Circuit Breaker Open, the object is not optimized due to the temporary unavailability of an engine component.
• ccb : Cache CallBack, the object is served by the proxy from the cache (in the case of an object that has not yet been included in an A/B test)
• of : Overflow, indicates that the overflow system is in place. The following flags specify the result:
  • !id : no ID present
  • exp : the session has expired
  • !conf : no configuration found
  • !en : not enabled
  • wen has been activated
  • at : enabled
  • say : disallow, the user was redirected to the waiting page
• r HTTP redirection made by Fasterize

X-Unique-Id

The header X-Unique-Id corresponds to the unique request identifier.

💡 Please provide this value to support in case of a problem to facilitate analysis.

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