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Extension for firefox and chrome to modify headers
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SimpleModifyHeaders V 1.6

Extension for firefox and chrome. (The extension can be install via this link for firefox and via this link for chrome)

The extension rewrite the headers based on a rules table.

The extension can be start and stop via the button on the top right.

To save and apply the modification, you need to click on the save button.

It's possible to:

  • export the configuration in a file (json format)
  • import the configuration from a file , it support the format of the Modifyheaders plugin

Rules table

The rules table contains lines with the following parameters :

  • action : add, modify or delete a header field
  • header field name
  • header field value
  • comment : a comment
  • apply on : "request" if the modification apply on the request headers or "response" if the modification apply on the response headers
  • status : on if the modification is active , off otherwise

Url pattern

We can choose the urls on which the modifications applies by modifying the url pattern :


The parameters button permits to :

  • Activate debug mode: show detail log messages in the extension debugging console of the browser.
  • Show comments : show comments field on the config panel
  • Filter URL per rules : activate the possiblity to filter url for each rules on the config panel, the header field will be modify only if the url contains the configurated value.

Firefox specific issue

According to the version of Firefox, the addition of a new header behaves differently. In the latest version, when you choose the "add" action and the header exist, it appends the value, while in the old version, it replaces it. If you want to modify an exiting header, you should use "modify" instead of "add"

Extension permissions

In order to work, the following browser permissions are needed for the extension:

  • storage : needed to store the configuration and the rules
  • activeTab, tabs : needed to show the configuration screen in the browser tab.
  • webRequest,webRequestBlocking,<all_urls> : needed to modify the headers according to the rules table.


The code is opensource under Mozilla Public License 2.0

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