Chrome extension chrome.webRequest API - Some http request headers not coming in request headers

Question

I was working on chrome extension with motive of intercepting all HTTP(S) requests/responses and log all headers into persistent file (on disk). I was almost close to my goal. But when I looked some requests closely, I found that in many requests " If-None-Match " and " If-Modified-Since " are missing in requestHeaders . Though, I can see them in Network panel displayed by the Developer Tools.

I tried hard to figure out any patterns, causing such behavior. But, unfortunately there is no such pattern.

Anybody please help.

Answer 1

The receive the list of requestHeader is necessary to use the onBeforeSendHeaders event from chrome.webRequest API .

In the onBeforeSendHeaders description is mentioned that some headers are not available for reading/processing:

• Authorization
• Cache-Control
• Connection
• Content-Length
• Host
• If-Modified-Since
• If-None-Match
• If-Range
• Partial-Data
• Pragma
• Proxy-Authorization
• Proxy-Connection
• Transfer-Encoding

I'm afraid you will not be able to read or modify these headers, because it's an API forced limitation.