Steem Developer Portal
Most people who will be implementing OAuth2 will want to find and utilize a library in the language of their choice. These libraries, while not necessarily built by Steemit, should support the SteemConnect API.
If you’re wondering what SteemConnect is, go here.
SteemConnect SDK - https://github.com/steemit/steemconnect-sdk
steem-connect-firebase-function - https://jakipatryk.github.io/steemconnect-firebase-functions/
A TypeScript library that can help you build applications with SteemConnect and Firebase.
Sc2 SDK PHP - https://github.com/hernandev/sc2-sdk-php
Easily integrate STEEM blockchain into your PHP applications, though SteemConnect.
Social Auth SteemConnect - https://pypi.python.org/pypi/social-auth-steemconnect/0.0.2
Pluggable authentication backend for python-social-auth, that allows authentication via SteemConnect (v2).
steemconnect-python-client - https://github.com/emre/steemconnect-python-client
steemconnect-python-client is a simple yet powerful library to interact with the Steemconnect.
omniauth-steemconnect - https://rubygems.org/gems/omniauth-steemconnect/versions/0.1.0
Ruby Omniauth2 Strategy for SteemConnect.
SwiftyConnect - https://github.com/caspernikus/SwiftyConnect
SteemConnect Library for iOS / Swift.
SteemConnect4j - https://github.com/hapramp/steemconnect4j
Steemconnect SDK for Java.