Google AdWords API Team Offers Sandbox For Developers

The AdWords API Sandbox is an environment that replicates the API of the live site, for developing, testing and debugging applications that use the AdWords API. When a developer logs in, AdWords accounts are automatically created in the Sandbox, then the developer can create and run campaigns, adgroups, creatives, and other operations on those accounts without incurring any quota. There is no quota on the Sandbox system — users are free to make all the calls they want. All account, campaign, adgroup, creative and criteria data that you submit can be read back as usual. However, the extra information based on usage and ad impressions such as traffic estimates, statistics, reports, and keyword suggestions, will be fake. The details on fake data are listed throughout this document. The Sandbox is not meant for load testing.

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Fair enough. It would be even better if they back off their intention to charge for AdWords API access in future.