Modify the response body of HTTP requests with Chrome extension [duplicate]

Question

I am working on a Chrome extension. I would like to modify some contents when the (very first) page load happens. I wonder if I use the method getContent() in chrome.devtools.network.onRequestFinished.addListener, how can I modify the content after it is returned from the method?

Is this method only for network/traffic observation? Can I modify the response body?

Answer 1

This has never been possible.

See this bug in the Chromium project (from Nov. 2011):

• https://bugs.chromium.org/p/chromium/issues/detail?id=104058

There are a couple relevant discussions on how to work around this limitation for certain use cases:

• Insert code into the page context using a content script
• https://groups.google.com/a/chromium.org/forum/#!msg/apps-dev/v176iCmRgSs/iM-72Evf8JgJ

Based on some of the discussion in the Chromium bug DB, I'd guess that modifying the content of the existing request may never be allowed for security reasons, but reading the response and redirecting might be allowed (someday when all the blocking issues are resolved).