I'd like to upload video files on a CKAN portal.
Does CKAN support uploading media files eg .mp4
Yes, you can upload media files as .mp4. They will be uploaded in your filestore, from where you can download them later on. About the views, the data explorer wouldn't preview the video file by default. I am not 100% sure if the video preview was developed but it was added to the roadmaps some time ago.