Google is offering to host enterprise web applications on its own infrastructure with a new tool for developers, App Engine.

It isn't the first to do so -- App Engine will compete with similar services such as Amazon's Elastic Compute Cloud and Salesforce's Appexchange -- but it may be the cheapest, as Google's basic services will be free.

Google's goal is to make it easy to get started with a new web application, and then make it easy to scale when that application reaches the point where it's receiving significant traffic and has millions of users, Google said in its new App Engine blog.

App Engine is based on technologies Google already uses. It is powered by Bigtable, a distributed storage system currently used by its Google Earth service, and by Google's own file system GFS.

The search giant is treading lightly, so far. The version launched on Monday is a preview release, and is by no means feature complete, according to Google.

Only 10,000 developers will be able to sign up initially, but that number will increase.

During the preview period, capacity will also be limited. Applications will for example be able to use 500M bytes of storage, and transmit up to 10G bytes of data per day. Google expects most applications will be able to serve around 5 million page views per month within those limits.

Google is keeping mum on how it will price the service, but applications operating within the limitations of the preview release will remain free, even when App Engine goes live.

App Engine will initially only support applications written in Python, but Google is looking to add support for other languages as well.