I’ve been doing youtube for a few months now, and I have recently been experiencing a problem. Whenever I play the preview of the video, it freezes for a short amount of time when the clip changes to another clip or there is a split in the clip. It only happens once in a while, but if the problem is still present before I export the video, then the video has the same choppy problems. The video playback is also extremely choppy if the clip has the chroma key simple on it. I use 17.10.02, and while looking at the forums for a while, I found out that choppy playback is fixed in this version. I want to fix this problem because I am really excited to post this new video, but I don’t want it to be choppy. Thanks for reading! 
This usually means your clip is not working well for seeking and editing. You need to convert it to edit-friendly format by using the menu in the Properties panel. When it is done, it creates a new file that you need to open and use. Shotcut does not automatically replace your old clip with the new one.
Some things like this are heavy, and it is going to be choppy in preview. There is nothing you or I can do about it. Did you view the result after export?
I don’t have the best system (i7-7700k, 32gb ram, Win 10, GTX 1070), when applying filters, cuts, transitions, Shotcut doesn’t play smoothly for me either. But the final product plays awesome for me. Never had a bad export, except for the mistakes I make during editing.
You can always install a different version and keep your current version.
I wrote this tutorial: Multiple Installations of Shotcut - Windows 10
And you can always go back to what version you wish to go back to.
All of the versions are available here: https://github.com/mltframework/shotcut/releases/
I should also point out that Settings > Realtime has an effect on this (the latter issue with playback choppiness with effects). Turning it off can use more threads (depends on your CPU thread count), but will give a different kind of choppiness because it does not drop video frame updates to try to keep audio continuous - it shows all frames regardless how long it takes and may play slower than realtime.
Just tried saving the video and force quitting shotcut (I have a mac.) The freezing problems are gone, but come back after a while. The chroma key is still choppy, but on export it is all fixed.
Oh, on macOS there is a different kind of choppy playback bug that I have seen that is remedied by restarting Shotcut. At one point, I had a preview frame rate throttle of 12.5 fps in place to prevent the problem, but I removed that in v17.11. Maybe it was not a foolproof bandaid, but I have not found a full fix for it (might require updating our GUI toolkit).
When I opened shotcut, it said that there were no available updates 
You have to click the message to ask it to check. If you are really using Shotcut, then it will say there is an update if you click it. There have been 8 updates since v17.10!
About 2 hours ago, I clicked on the message and nothing happened…
Thanks 
Just wondering, would Chroma Key Advanced make a difference in the playback framerate? Whats the difference between the two?
Chroma Key Advanced will not help with that. The two are completely different implementations from two different authors with Advanced having many more parameters some of which are difficult to understand. In short, Advanced might work better with some trickier backgrounds or edges, and also it supports multiple instances working together using the Operation parameter.
Thanks for the information.
I turned off the realtime but when i overwrite the clip on to the current track, it’s still choppy, and when export too, please help me!