Another picture

Looks like rough bluegrass to me. I have a lot of it in my yard. It seems to be more prevalent in shady and wet areas. I am trying Tenacity on mine. Is that were you find the grass you pictured, shady and wet areas?

Could be rough bluegrass/poa trivialis, but hard to see from that distance, you know if it is as it looks like Kbg but the stolons are very long and creepy and it tends to be lighter in colour. I had an outbreak which I hated so I dug up each patch wen I sacrificed and overseeded the whole lawn. It looked terrible initially with big patches of soil in places, but over the weeks it did well and within six weeks the whole lawn looked excellent and blended without any of this grass

It's growing in a sunny area that isn't all that wet most of the time. It just has popped up in a few areas and looks "weedy" before mowing is needed.

I'm going to be over seeding soon and I wanted to try and identify what type it is so I don't include in my seed I buy.

So you're sayin it has very fast growth?

Does it grow in a single stem almost like a green onion? Does it pull out of the ground ? Roll the stem in fingers, is it triangular instead of round?

Could be some younger Sedge...?