i saw a blue streak in the sky what is it?

Was it at night or during the day?

Was it clear or cloudy?

Please try to be more detailed in your description of the environment at the time and you might receive more meaningful / helpful responses.

If it was a clear night, then the most likely cause is a meteorite.

If it was a cloudy night, then it could have been a laser pointer, though blue laser pointers are rare.

If it was on a cloudy day, then it could have been a low flying aircraft, but you would have heard the noise.

If it was a clear day, then it may have been a vision problem. I mean a problem with your sight.

Most likely a meteor. They usually appear in the sky as a blue streak for a few seconds or less and then disappear as they burn up in the atmosphere.

it might be a meteor because there's a meteor shower coming up next monday. you can google it.

Was it wearing Red undies.

It was a meteor.

It was your LAST brain cell...