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Please check devices and browsers before attending the online class. 
If you see an afterimage of the mouse in the online class, please click the Windows + Ctrl + Shift + B keys. You can remove it to reset your graphics card.
Table of Contents
Click on the guide to jump directly to it!
PC
Check the Operating System
Please check if you are using one of the following operating systems.
•
Windows : Windows 8.1, Windows 10
•
macOS : OS X 10.12 or higher
Check the Browser
For PCs, please use the Chrome browser.
If you use other browsers, you cannot access to the online class.
Allow Camera and Microphone Access for Joining the Online Class
When joining the online class, be sure to Allow access to microphone and camera in the permission pop-up window. If not allowed, you will not be able to use the online class.
Check Internet Speed
If your internet speed is slow, sometimes the screen will be remained black.
It should be at least 5 mbps when accessing the PC
If you've done this far and it still doesn't work, please check the followings!
Mobile
Please use the mobile guide as guidance for students.
Teachers, please be sure to connect to the PC for smooth classes.
Please do not use other applications for online class on mobile.
Most of problems when connecting on mobile are caused by using multiple applications at the same time. Please pay attention and avoid doing so.
Check the Operating System
Please check if you are using one of the following operating systems.
•
iOS : iOS 12.0 or higher
•
Android : Android OS 5.0 or higher
•
Others: Users with Linux, Chrome OS, or other operating systems
Check the Browser
For mobile devices, please use the Chrome or Safari browsers.
You cannot access to the online class with other browsers.
Allow Camera and Microphone Access for Joining the Online Class
When joining the online class, be sure to allow access to microphone and camera in the permission pop-up window. If not allowed, you will not be able to use the online class.
Check Internet Speed
If your internet speed is slow, sometimes the screen will be remained black.
It should be at least 2.5 mbps when accessing the PC
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