How to have Fiddler\ other application automatically intercept and modify HTTP requests parameters?

Question

I work with a website that I dont own\ coded. Now, I need to change one of the params on the requests that are sent from this website to the server.

Example: From:

https://google.com/search?count=20

To:

https://google.com/search?count=40

I tried and succeeded changing the param with Fiddler but I want it to be done automatically for every request that is sent from my pc.

I also tried Requestly, which is a chrome extension that is capable of modifying params, but it also messes with the response headers. Instead of sending:

Accept-Encoding: gzip, deflate, br
Accept-Language: he-IL,he;q=0.9,en-US;q=0.8,en;q=0.7
Cache-Control: no-cache
Connection: keep-alive
Content-Type: application/json
sec-ch-ua: "Google Chrome";v="95", "Chromium";v="95", ";Not A Brand";v="99"
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: "Windows"
Sec-Fetch-Dest: empty
Sec-Fetch-Mode: cors
Sec-Fetch-Site: same-site
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36

as headers, it only sends:

User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36

Any suggestions here?

Answer 1

Requestly doesn't modify the response headers if you have configured a QueryParams Rule

You can create a Modify QueryParams rule like this

As per the documentation

• The rule will add the parameter q with value 40 if the parameter doesn't exist
• The rule will change the value of parameter q to 40 if the parameter already exists in the URL.

For Requestly related questions, I'd suggest using the QnA section - https://github.com/requestly/requestly/discussions/categories/q-a