There may be the following reasons why your computer lags when watching videos:
Hardware problem: The computer's hardware configuration, such as CPU, graphics card, RAM, etc., is too low, or there is not enough space on the hard disk, which will cause your computer to have lag and delay when loading and playing videos. It is recommended to upgrade the hardware configuration or add more storage space.
Software conflict: The video player or other software installed on your computer has a conflict with your system or other programs, such as a missing encoder or decoder, which can affect normal video playback. You can try to replace the player with another one or uninstall the conflicting application software.
Virus infection: If your computer is infected with a virus or malware, it may take up a lot of system resources and cause your computer to run slowly, which can also lead to video lag. You can install antivirus software and run a full scan to identify and remove viruses.
Network problems: Watching online videos requires a fast internet connection, if your internet connection is unstable or too slow, it can only cause the videos to load slowly. You can try to turn off other devices that are using the network, change the network environment, restart your router, etc. to improve your network connection.
In summary, the lagging of a computer while watching a video may be related to hardware and software issues, virus infections, and network connection problems, among other things. It is recommended to follow these points and if the problem persists, please contact a professional for more technical support.