I've seen streaming services spoil an episode with just the thumbnail. I can't remember what show's twist was ruined for me, but I'm pretty sure it was Netflix.

Netflix also has a really annoying habit of re-ordering seasons. For some bizarre reason shows like bake off are listed with the most recently added series first. For some shows that might not be a huge problem but in the first episode of one series they actually recap the winners of all previous series, spoiling several years of programing for unwary netflix viewers.

At least one extremely typical problem on Netflix and basically every other streaming service is that the episode thumbnails (which I usually have to go take a look at just to find out how many episodes there are) will ruin any cliffhangers. If a character's survival seems uncertain, the uncertainty will be lessened quite a bit by seeing their face in the thumbnail of a subsequent episode.

I don’t even want to see the title of an It’s Always Sunny episode before the cold opening.

Titles don't usually spoil too much. At least the writers expect you to see them.

At least with Always Sunny the title is usually the punchline to a joke they set up in the cold open and then drop the title card.

Dee: "No that's a bad idea. Usually when you get involved somebody gets hurt."

Frank: "That's ridiculous. I'm just paling around with the guys. How is anybody going to get hurt?"

Title Card: "Frank Sets Sweet Dee on Fire"

A lot of translated titles contain slight spoilers though, for example "predestination" becomes "time paradox" in Korean, it immediately gives you a hint of some part of the twist.

Maybe because it was a book already?

Otherwise there's somebody working there that is a monster.