Streamlink is a command-line utility which pipes video streams from various services into a video player, such as VLC.
The main purpose of Streamlink is to avoid resource-heavy and unoptimized websites, while still allowing the user to enjoy various streamed content.
There is also an API available for developers who want access to the stream data.
Streamlink is built upon a plugin system which allows support for new services to be easily added.
Most of the big streaming services are supported, such as:
... and many more.
A full list of plugins currently included can be found on the Plugins page.