From the text of Find Familiar (emphasis mine):

Additionally, as an action, you can see through your familiar's eyes and hear what it hears until the start of your next turn, gaining the benefits of any special senses that the familiar has.

So, every turn that you're using your familiar's senses, you're using your action to do so. RAW, you should still be able to move and use bonus actions, but (unless you have another feature that allows for multiple actions during your turn), you would not be able to take actions like attacking or casting a spell.

Quote from AnselMerric >>

If you've got your bat familiar on your shoulder and you're seeing and listening through its senses, how close to normal actions are you? Can you move/attack/cast/etc as normal, but with blindsight as an added ability?

 yes

there are some things that can only attack if you are in the same space, for example a swarm of bats

because its the minimal in 5e while in combat

Guys a bat can lift 15 pounds. It’s literally a bat how.

bread

BREAD WHERE? 
ME WANT BREAD

the bit is sooo long ranged

Because

It's hilarious that in dnd, if you got enough bats together they could go murder some commoners. 
If you had a couple druids cast conjure animals and conjured 8 bats each, that would be enough to go murder some villagers with. Not many, but still.
Bonus points if the druids then turn into bats and join the swarm. 
Beware the bats.

can a bat carry another tiny object?

Quote from Arcanavore >>

Perhaps this is the only intelligible comment on the Bat thus far... 

Taking a Bat as ones familiar allows you to pinpoint the presence of invisible creatures, like a Living Unseen Servant, with the bat's echolocation. Who needs See Invisibility now??

 

Bread

 

 I agree with every word. 

So. . .

Bread.

What bout bread? Though what kind?

5260

why his face look like that tho

Quote from abyissymomo >>

why his face look like that tho

 Well, you see, 

Quote from Skog >>

Does Blindsight penetrate Darkness?

 Not necessarily. The basic rules entry states nothing of the sort.

This means that a bat's echolocation would be blocked by darkness, according to a purely RAW interpretation. This is more than a bit silly though, especially since penetrating darkness is the exact reason bats evolved echolocation in the real world, so I'd rule that a bat can see in normal and magical darkness within the radius of its blindsight.

EDIT: Nevermind, not requiring sight to perceive implies that darkness, magical or non-magical, would not affect you. So I guess blindsight really is just darkvision but better.

bats in d&d have a 5 foot long snout

pronunciation be like

b       a        t

it swoops done and bites