# Guide to OpenIG
Chapter 2. How OpenIG Works

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## 2.1. How It Works In A Nutshell

The underlying core of ForgeRock Open Identity Gateway is based on a reverse proxy architecture. All HTTP traffic to each protected application is routed through OpenIG, enabling close inspection, transformation and filtering of each request. By inspecting the traffic, OpenIG is able to intercept requests that would normally require the user to authenticate, obtain the user's login credentials, and send the necessary HTTP request to the target application, thereby logging in the user without modifying or installing anything on the application. In its simplest form and basic configuration, OpenIG is a Java-based reverse proxy which runs as a web application. Enable the Form-Filter replay module and OpenIG automatically log users in when a timeout or authentication page is detected. Additionally, enable the SAML2 service and OpenIG becomes a SAML2 endpoint. In this mode of operation, OpenIG receives and verifies the SAML2 request and then logs the user directly into the target application.