They may also provide these services through pay-per-usage pricing.
SaaS (Software-as-a-Service), also known as cloud-based software or cloud applications, is application software hosted in the cloud. Users access SaaS through a web browser, a dedicated desktop client or an API that integrates with a desktop or mobile operating system. Cloud service providers offer SaaS based on a monthly or annual subscription fee. They may also provide these services through pay-per-usage pricing.