As Spreedly grows and improves, it becomes necessary to make backwards-incompatible changes to our API. Rather than breaking our clients every time we change the API (or, just as worse, never improving the API at all) we version the API and maintain deprecated versions for a defined period, currently guaranteed to be a minimum of one year from the release of the next version of the API. So version 3 of the Spreedly API will be maintained for a minimum of one year after the release of version 4.
While we encourage everyone to build against the most recent version of the API (always indicated at the bottom of the manual pages), we understand that existing installations may need to continue working with deprecated API versions and thus we maintain the documentation for all deprecated versions, accessible from this page. Note, however, that you can mix and match API versions, so even though you might be using a deprecated API version in one place in your application, you can still implement new functionality against the newest version of the API.
When we prepare to permanently retire a deprecated version of the API, we will check for any paying clients still using the deprecated version and contact them via their contact information to help them move to the most recent version. Usually the move is very straightforward, and we'll assist as much as we can in making it happen. Once an API has been deprecated, we will fix any bugs in functionality it already supports, but we will not add new functionality to it. To get access to new API features, you must move to the latest API version.