Apps and websites that use the Google Maps API will soon have to pay $4 per 1,000 visitors Google announced today.

There is an allowance for small sites – the first 25,000 map-loads a day are free. The toll has been on the way since Google updated the Maps API's Terms of Service in April and was scheduled to kick in at the beginning of October. It could be significant cost for developers: an app using the JavaScript Maps API for mobile and clocking in 100,000 users will now have to shell out $300 a day.

The visitor allowance is lower for those with styled maps (visually customised ones), who will have to pay $4 per 1,000 map loads after the first 2,500 – this goes up to $8 per 1,000 loads after 25,000 loads.

A "map load" counts as a user opening a page with the app on it. The degree to which a user interacts with a map once it has been loaded has no impact on the usage limits.

Developers who use the Maps API have three options: either bring their usage numbers down below the threshold, pay the overuse fees or cough up $10,000+ for a Google Maps API Premier licence.

The Premier licence has been around for a while, and contains added features such as advanced geocoding, customer support, and full control over advertising. The prices start at $10,000 per year, increasing according to the number of site visitors.

Sites that fail to buy a licence or enroll for the metered payment won't have their maps taken down, but if they overclock the visitor threshold regularly, a message will start to appear to users, and Google Sales will start to get in touch to "discuss licensing options".

Google is introducing a payment dashboard to help people on the pay-for-overuse model manage their visitors and payments.

Not everyone who has a Google map on their site will be affected. It's possible to embed a Google map on a site or blog without using the API – and there is nothing to indicate that that will change. ®