Arjun can find query parameters for URL enpoints. If you don't get what that means, it's okay, read along.

Web applications use parameters (or queries) to accept user input, take the following example into consideration

https://api.example.com/v1/userinfo?id=751634589

This URL seems to load user information for a specific user id, but what if there exists a parameter named admin which when set to True makes the endpoint provide more information about the user?
This is what Arjun does, it finds valid HTTP parameters with a huge default dictionary of 25,980 parameter names.

The best part? It takes less than 20 seconds to go through this huge list while making just 50-60 requests to the target. Here's how.

• Anomaly detection with 9 factors
• Supports GET/POST/POST-JSON
• Automatically handles rate limits and timeouts
• Can import targets from BurpSuite, text file or a raw request file
• Can passively extract parameters from JS or 3 external sources
• Makes ~50 requests in 20 seconds for checking 25,980 parameter names

Note: Arjun doesn't work with python < 3.4

A detailed usage guide is available on Usage section of the Wiki.

Direct links to some basic options are given below:

• Scan a single URL
• Import multiple targets
• Save output to a file
• Use custom HTTP headers

Optionally, you can use the --help argument to explore Arjun on your own.

The parameter names wordlist is taken from @SecLists.