It's smaller.

The cue ball is a different size. It's smaller and able to go through a "tunnel" that stops the larger balls.

most tables have a larger cue ball. Diamond tables use a sensor that can detect the cue ball from the other balls.

The cue ball is either larger than the other balls, or has a magnet in it. No 1 is also correct about the new Diamond tables with lasers that, as far as I can tell, essentially measure how "white" the ball is to determine if it's the cue ball.

There is a magnet in the cue ball that makes the cue ball slightly heavier. When the cue ball goes down in the pocket it will travel in a track. Just before it gets to the window, there is an adjustable magnet that will attract the cue. If the magnet isn't set up right you will have the cue ball get stuck in the ball return.

the cue ball it smaller allowing it to travel a separate track to the other end of the table. (this could not possibly work if it were larger)

There are two exits on a coin operated table. The number balls come out at one end of the table into a large opening. The cue ball comes out into a much smaller landing that only holds one ball. There is a system of runways leading from each pocket to a holding place waiting for a coin. There are two holes in this runway, the larger cue ball rolls over the smaller hole and always returns to the outside of the machine because of players scratching. The smaller number balls fall into the hole and into the waiting area awaiting the next game.

Go with the Magnet and laser answers
Most will be magnets-And they are not always centered thats why so many lousey cue balls on bar tables

I'm sure different maker of tables have different ways of doing things, but I do know that the cue ball is SMALLER than the numbered balls. All of the tables that we use around my area have a hole that only the cue ball will fit down, and that is how they get separated. I've never seen a cue ball that was LARGER than a numbered ball, because that just wouldn't work.

Its actually larger/heavier than the others.
Thats why ocasionally you'll see good shooters sometimes want to use a normal cue ball. This is due to the fact that its easier to get a normal/lighter cue ball moving around the table easier than a bar box cueball.

They are actually heavier not lighter as some have mentioned.