User Agent Spoofing

When a browser or bot requests a webpage, it sends a User-Agent HTTP header containing a string of text that describes the client. So, if you are using Firefox on Windows to browse the web, it is sending this string of text to every website you visit, where it is visible by the server and any embedded third-party scripts like banner advertising:

Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:142.0) Gecko/20100101 Firefox/142.0

If you need valid User-Agent strings to use in your spoofing adventures, consider some of these resources:

• WhatIsMyBrowser.com has a pretty comprehensive set of pages covering a wide variety of user agents.

How to spoof your user agent depends on the type of software you are using:

By default, curl sends a User-Agent string in the format curl/X.Y.Z, where X.Y.Z represents the version of curl installed on your system. For example, curl/8.4.0. There are several ways you can pass custom User-Agent strings:

Use the -a flag to directly set the User-Agent:

$ curl -A "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:142.0) Gecko/20100101 Firefox/142.0" https://example.com

You can make up an entirely custom User-Agent as well. Be forewarned however that it works better if you set one that lets you blend in with the crowd:

$ curl --user-agent "MyCustomAgent/1.0" https://example.com

Use the –user-agent flag, which works the same way as -a:

$ curl --user-agent "MyCustomAgent/1.0" https://example.com

Since the User-Agent is passed as an HTTP header, you can also change the User-Agent by using t -H flag, which lets you manipulate headers:

$ curl -H "User-Agent: MyCustomAgent/1.0" https://example.com