The FilePreviews.io service is composed of a very simple API organized around REST.
There's an endpoint that can be used to request a preview, which happens asynchronously. The returned results are useful for different scenarios, allowing you to poll until requested previews and metadata are available, or use webhooks.
Libraries are available in several languages.
Currently, the FilePreviews API is versioned with a URL segment, such as /v2/. The current production version of the API is Version s, so your calls should use /v2/ as the version segment.