google maps api key what to use

Question

I don't get it, why do I need an API KEY?/

If I place map code into my site using:

<script src="https://maps.googleapis.com/maps/api/js?v=3.exp&sensor=false"></script>

it works.

If I place code into my site using:

<script src="https://maps.googleapis.com/maps/api/js?key=API_KEY&sensor=flase"></script>

where API_KEY is my api key it also works.

What is the difference here? Which one should I use and why?

Answer 1

It's true that the Google Maps JavaScript API v3 does not require an API key to function.

However, Google says you should use an API key to monitor your usage. In case you exceed your usage limits, you'll know about it and Google can contact you.

The usage limit is 25,000 map loads/day/API.