Firmware Version Required:
5.3.2, 5.4.0
Downloads:
Mongoose is my preferred option, but seems to cause some issues for some.
Mini Web is another lightweight option to use on your Windows PC. The only differences are that you can't set your folder; everything has to go into MiniWeb's htdocs folder, and it uses port 8000 instead of port 8080. If you have Skype running, you'll have to close it before starting MiniWeb, then can open it again. (There may be other programs that also use port 8000).
There are, of course, many additional ways you can self-host files (WAMP, XAMPP, etc.), but these are the easiest to set up (no installations). The guide will refer to Mongoose for all steps, but substitute for whatever you are using when necessary.
Windows:
1. Double-click on mongoose-free-5.6.exe to start it
2. Right-click on the Mongoose icon in your status bar
3. Click "Set shared directory:" and choose the folder you have your files in
4. Right-click on the Mongoose icon in your status bar again
5. Click "Go to my address: <URL HERE>"
If it loads, congrats! It's working.
Note the URL, this is what you'll be typing into your Wii U.
OSX:
1. Place your downloaded Wii U hacks in a folder wherever you like and copy Mongoose to that folder
2. Go into "System Preferences/Sharing" and enable file sharing
3. Add the folder where everything is located (from Step 1) to your "Shared Folder" by clicking on the +
4. Click on "Options" and make sure you share files using both SMS and AFP
5. Double-click on the Mongoose app in your hacks folder to start it
6. Click on the Mongoose icon at the top right corner of your screen and select "Go to my address: <URL HERE>"
If it loads, congrats! It's working.
Note the URL, this is what you'll be typing into your Wii U.
FAQ:
Right-click on Mongoose and click Exit. Then restart it and try again. If you're on Windows, make sure you allow the connection to go through your Windows Firewall by going to "Control Panel\System and Security\Windows Firewall\Allowed apps" and adding mongoose-free-5.6.exe to the list. Make sure it has check marks for Private and Public.