What are reverse proxies and how do they differ from forward proxies

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Proxy servers can be categorized based on various factors including their purpose, usage methods, and levels of anonymity, among other criteria. Classification also depends on the location of the intermediary server and the functions it performs, distinguishing them as either reverse or forward (common) proxy servers.

A reverse proxy server takes user requests, routes them through itself, and then forwards them to the destination server where the requested data resides.

How reverse proxies work

Here’s a breakdown of how reverse proxies function:

  1. A user sends a request from their device, such as opening a web page in a browser.
  2. This request is directed from the web browser to the reverse proxy.
  3. The reverse proxy then forwards this request to the destination server.
  4. The destination server sends its response back to the reverse proxy.
  5. Finally, the reverse proxy relays this response to the user, displaying the requested web page.

In this setup, the reverse proxy acts as an intermediary between the client (such as a web browser or an application) and the end server. While the client can see the user’s IP address, it cannot determine the address of the end server.

Use cases of reverse proxies

Considering the location of reverse proxies, they can be effectively used in several scenarios:

  • Distributing incoming requests among different servers in a cluster to ensure an even load;
  • Caching static elements of a web page, such as images, styles, and scripts;
  • Enhancing the performance of web applications through data compression or by minimizing HTTP requests;
  • Protecting the end server from DDoS attacks through traffic filtering;
  • Anonymizing the IP address of the end server;
  • Redirecting some requests to operational backup servers to maintain fault tolerance.

From these traditional functions, it's clear that a reverse proxy plays a critical role in ensuring the stable operation of the end server and in safeguarding it from various threats.

What are forward proxies and what are they used for

Reverse and forward proxies serve different roles based on their location and functions. To understand the difference, let's examine how forward proxies operate:

  1. The user sets up a proxy on their device or within their software, and, for example, opens a page in the browser.
  2. The request is sent using the proxy's IP address, not the real IP address of the user's device.
  3. The final server receives the request from the proxy rather than directly from the user.
  4. The server sends a response back to the proxy server, which then forwards it to the user.

In this scenario, the proxy acts as an intermediary between the user and the final server, which could be a web browser or application.

It's important to recognize that forward proxies vary in their levels of anonymity, which classifies them into transparent and anonymous proxies. Transparent proxies do not conceal the user’s original IP address nor the fact that a proxy is being used, and they are typically employed for routing requests.

Anonymous proxies, on the other hand, completely mask the user’s IP address and obscure the use of a proxy. They are particularly useful for several purposes:

  • Bypassing geographical restrictions and IP-based blocking;
  • Avoiding limitations on the number of accounts associated with a single IP address;
  • Performing automated actions without the risk of being blocked;
  • Protecting user traffic from interception and other malicious activities.

Forward proxies can be hosted in various locations such as data centers, ISP servers, or mobile devices, each providing different levels of accessibility and security.

Differences between reverse proxies and forward proxies

In conclusion, let's compare forward and reverse proxies based on their main characteristics.

Characteristics Reverse proxies Forward proxies
Location Installed on the end server Installed on the user's device
Anonymization method Hides the IP address of the end server from clients, for example, web browsers or applications Hides the real IP address of the user from the end server
Traffic management Controls and filters traffic coming to the server Routes and protects user traffic
Setup process Installed by system administrators or owners of dedicated servers through special software Can be installed by a regular user through operating system settings, applications, or programs
Use cases
  • Access to region-blocked content;
  • Performing automated actions on web resources without the risk of blocking;
  • Bypassing limits on social media.
  • Providing additional security;
  • Ensuring distributed load on the end server.

Thus, ordinary users and specialists in fields like SEO, SMM, and E-commerce typically choose forward proxies for their projects. Conversely, reverse proxies are preferred by owners of corporate networks, web developers, and server administrators.