This wikiHow teaches you how to check if someone is online on Snapchat by looking for chat, message delivery, and typing indicators.
EditSteps
EditChecking For The Blue Dot
- Open Snapchat. Snapchat's icon is yellow with a white ghost on it.
- Swipe right on the screen. Doing so will reveal the Chat screen.
- Tap on a user. Doing so will open up a chat window with them.
- Look for a blue dot. If both you and the other user have a chat window open at the same time, a blue dot appears above the left corner of the text box.
- Alternatively, if you get a notification on your device's home screen that a user is typing, they are using Snapchat at the time of the notification.
EditChecking A Snap's Delivery Status
- Open Snapchat. If you've recently sent a Snap to a person, you can check to see if they've opened it, which can be a good indicator as to whether they've been online.
- Swipe right on the screen. Doing so reveals the Chat screen.
- Review your Snap's delivery status. It's located just underneath the recipient's username.
- If the user has opened the Snap, it will read as Opened.
- If the user hasn't opened it yet, it will read as Delivered.
Source: http://www.wikihow.com/Know-if-Someone-Is-Online-on-Snapchat