If you prefer, you can use your username to log in, instead of your email address. Your username is unique and cannot have special characters or spaces. Sometimes it is automatically generated when you create your account. Below are instructions on how to locate your username.
When logged in to your account, simply tap your picture and select "Your Profile" or "Settings". Either will display your username. You can also edit your username in the Account Settings.
On Android and iOS:
1. Choose the profile tab located towards the bottom of the app.
2. Your display name is listed towards the top. Please note that your display name and username are different. The display name will be listed on your leaderboard, whereas your username is unique.
3. Tap "Settings"/gear icon and your username will be detailed, along with your Duolingo account info. You'll be able to edit your account info here, as well.
If you need to change your username, please follow these instructions.