Looks like a pit / lab mix, and it looks more lab than pit.
I agree with Wyldfire. Careful until you know its temperment, and then still be careful. We had a pit mix I found on the side of the freeway (which became his name). He was great with the family. Hell my son used to ride him like a horse. Then one day he got into a fight with my corgi over some table scraps and he went fvcking ballistic. We decided to give him another chance, and the second time around my wife, son and the corgi all got injured. I heard screaming, ran into the room, and saw blood everywhere. I went totally kung fu on it, and finally got it to submit. Kicks that I've knocked sparring partners out with barely had any effect on it. Pitbulls (even mixes) are bad mofos, and I was scared sh1tless. The next day it had to be put down, and it was a sad day. Since then we only take in puppies from breeders we trust.
Be careful!