I was using UE4 yesterday when all of a sudden my projects began to look jagged when I played them. I don’t think I did anything with the anti-aliasing. How do I fix this?
I did have my AA on when I took that screenshot
try to select “use default” from Show Drop down menu.
something wrong happened for sure
and btw, what’s your graphic card?
Tried that, didn’t work.
To answer your question, I’m using an Nvidia GeForce GT 240
Your card is so old to run the engine, however Lets see what’s the staff opinion about this issue.
But I’m sure it’s a hardware issue
I only encountered this problem just yesterday. I never had this happen before then, so I don’t think it had anything to do with my graphics card.
check this link
https://docs.unrealengine.com/latest/INT/Engine/Performance/Scalability/ScalabilityReference/index.html
I tried this and it worked. Thanks for that.
Did you make sure your engine Scalability settings is up as high as they can?
Click on settings right above your viewport and you should see engine Scalability in the list,
There are different options Low-Epic.
Mess with those 
i have the same problem i thought it was the way it looked on mobile but even in editor nothing changes when i change the graphics settings or the AA settings. What is the issue here?