Can I use my late 2013 MBP with Dell2515H? I'm thinking to get an external monitor for my MacBook Pro Retina display (late 2013 model).

What I would like to have is to get a 4K monitor or QHD monitor (Dell U2515H or P2715Q).

What I'm worried about is the font and icons size on the external monitor. Should I expect them to be tiny and hard to read text?

My graphic card is Intel Iris 1536 MB.
You can use 4K displays and Ultra HD TVs with these Mac computers:


MacBook Pro (Retina, Late 2013 and later) 
Mac Pro (Late 2013) 
iMac (27-inch, Late 2013 and later) 
Mac mini (Late 2014) 
MacBook Air (Early 2015) 
MacBook (Retina, 12-inch, Early 2015)


So yes, your MacBook will support a 4K external monitor. You can decide how big you would like your interface/text etc. to appear in system preferences the same way you can on your internal monitor.

Source: Apple Support Documents