Can one watch a video on Youtube that was recorded or uploaded by a Jew on Shabbat, or is this considered Maaseh Shabbat?
Since others are allowed to benefit from a melachah performed on Shabbos immediately subsequent to Shabbos even when the the transgressor did so in open defiance of Shabbos (O.C. 318:1) it would seem permitted to watch a video which is otherwise permitted to watch. If the uploader is a mumar there are poskim who are strict and require one to wait enough time after Shabbos for the melachah to have been performed permissibly.
Of course it is nevertheless distasteful to depend directly on chillul Shabbos so it would be inappropriate to rely someone transgressing Shabbos so you can watch it immediately afterwards.
With regard to something recorded specifically on Shabbos (i.e. it isn't something that happened to be on Shabbos but is specifically about Shabbos or so forth) it is possible that this is more severe because it is done for posterity and there is no immediate benefit to the melachah. As such it may be analogous to a situation such as a plant planted on Shabbos where the only rectification is for it to be uprooted (i.e. undone), see Biur Halachah 318 אחת משאר מלאכות.