Question Thumbnail Gradients - Images for YouTube

[SupahKent]

I have no idea where to post this, or even if I'm in the right place, but would really appreciate some help.
I've created a bunch of thumbnail images for YouTube which use gradients in some parts of the images.
All but these gradients look fine within the image. The gradients appear distorted and full of artifacts
after I upload them to YouTube. Before uploading, they look fine.

I'm saving them as 1280x720 PNGs. Can anyone tell me how to make these images crystal clear?
Is there another format I can save them as? I'm currently using a very old copy of Photoshop CS2,
if this matters any.

Thanks.

 

[Ralston18]

Go online to YouTube and find other similar images with gradients that look fine etc..

Then check their format and resolution.

Try editing a couple of your images (make a copies) to match, saved the edited copy, and then upload as usual.

Do the gradients look better? Or get worse?

Post what image edits you made and the results.