mitmproxy instructions

The v1.1.0 update to the Nintendo Switch Online app unfortunately changed the method used to log in to Nintendo accounts and, as a result, removed the ability to generate cookies within the script (i.e. without using the app). The following method can be used to intercept your phone's traffic to grab your iksm_session cookie from the app.

Obtaining your SplatNet cookie using mitmproxy

1. Download mitmproxy by following the instructions for your operating system here. Releases for Mac, Windows, and Linux can be found here. If you're on macOS and have Homebrew installed, you can run brew install mitmproxy.

2. Run mitmweb by clicking on the downloaded/installed file. You can also navigate to the folder and run ./mitmweb from the command line.

3. Obtain your computer's internal IP address:
   (Windows) Run ipconfig from Command Prompt/PowerShell and look under "IPv4 Address."
   (Mac) Go to System Preferences > Network > Wi-Fi > Advanced… > TCP/IP > IPv4 Address.

4. (Android) Go to Settings > Wi-Fi > long press to modify network. Set proxy to "manual" under advanced options. For proxy hostname, enter your computer's internal IP from before and enter the port as 8080.
   (iOS) Follow this guide.

5. Go to http://mitm.it/ on your phone and download/install the certificate.

6. Open the Nintendo Switch Online app on your phone, log in if you have not done so previously, and click on Splatoon 2 under Game-Specific Services.

7. In the mitmweb tab that opened before, look for the line that says https://app.splatoon2.nintendo.net/?lang=en-US. Grab the cookie value from the Request tab (in the format iksm_session=xxxxx where xxxxx is your cookie). Open config.txt and enter xxxxx as the value for cookie.

   If you do not have a config.txt file, the default format is provided below, which you can copy and paste into a new file:

   {
       "api_key": "",
       "cookie": "",
       "session_token": "",
       "user_lang": ""
   }