Controlling 12v DC LED strips using Arduino UNO
It's not safe for the MCU without transistors or so.

You can use some kind of LED driver (for example TLC5940 with on chip PWM) or ULN2003 as 8 channel low side switch (instead of 8 transistors, PWM is possible if you do it programmatically) or many others.

With single transistor it looks like:


Where R_1 can be about 1K and transistor can be any NPN that could handle led current.