Microsoft has announced that the Bing Search API will no longer be available free of charge to developers. The company is introducing a monthly subscription service, which it says will bring "fresher results, improved relevancy, and more opportunities to monetize usage of the Search API." The transition will begin in a few weeks and take several months to complete — the free Bing Search API will remain available throughout the process.

The API provides developers with the tools to integrate Bing's search mechanisms into their websites, allowing for internal and external content searches. It will be sold through the Windows Azure Marketplace and the full pricing structure will be made available at a later date. The starting price for the service will be around $40 per month for "up to 20,000 queries." The announcement has drawn criticism from developers working for non-profit organisations, as well as those with very low traffic. Microsoft replied saying it was "absolutely thinking about ways to enable smaller scale applications to keep experimenting with the API," and asked developers to "stay tuned for more details over the next several weeks."