Parallel Space - Parallel Space – Multiple accounts and Two-Face is free to use mobile app that helps you clone or run multiple accounts of the same app simultaneously, and use themes to style your unique space.
Surge for Mac - Advanced Web Debugging Proxy for Mac & iOS
App Cloner - Clone your Android apps so you can use multiple logins.
Charles Proxy - HTTP proxy / HTTP monitor / Reverse Proxy
2Accounts - 2Accounts is an up-to-the-mark tool that enables its global users to enjoy multiple accounts for messaging, multi-gaming, and run a double social account for work and personal life.
HTTP Headers - HTTP Headers allows you to quickly see the HTTP header information for the current URL.