When you click the [Register](https://stackapps.com/apps/oauth/register) link you're presented with this webform:

[![register app][1]][1]

If you're in a hurry and click *Register your Application* you'll find this error:

[![4 fields required][2]][2]

The fields Name, Description, Website URL and OAuth Domain are required.

You can probably dream up a name and a description but those pesky Website URL and OAuth Domain keep bugging me. Here is the shortest route to success:

|Field|Value| 
|-|-|
|Application Name | CanHazKeyPls |
|Description | CanHazKeyPls |
|OAuth Domain|bad.invalid|
|Application Website|bad.invalid|

And now click on the big blue *Register your Application*. 

Congrats, you now have registered an app. You find the key as the third item on your app registration page:

[![app registration][3]][3]

If you scroll all the way down you'll find a blue *Edit this App* button, allowing you to change any of the values you previously entered. So if you later do get an website or read-up on [Oauth flow](https://stackapps.com/questions/7857/what-exactly-is-a-valid-oauth-domain-name-for-registering-your-app) you can adapt your values accordingly.

Enjoy your new app and key!

<sup>credits for bad.invalid goes to Kevin Montrose in [his answer](https://stackapps.com/a/6406/18722) </sup>

  [1]: https://i.sstatic.net/xX06F.png
  [2]: https://i.sstatic.net/DtcwE.png
  [3]: https://i.sstatic.net/IlmBc.png