Understanding Forward and Reverse Proxy: Concepts, Uses, and Differences

On a weekend while searching resumes, the author introduces the topic of proxy servers.

Reverse proxy (reverse proxy): A proxy server that receives Internet connection requests and forwards them to internal network servers, then returns the server's response to the Internet client, appearing externally as a reverse proxy.

Forward Proxy

Forward proxy (forward proxy): A server positioned between the client and the target server; the client sends a request to the proxy specifying the target, and the proxy forwards the request to the target server and returns the content to the client.

This proxy model is common in everyday life, such as in “scientific internet access” technologies.

When a user wants to access a foreign website that is blocked domestically, they can use a proxy server that can reach the foreign site; the proxy forwards the request and returns the response, effectively enabling the user to browse the blocked site.

The process is analogous to renting a house through an intermediary.

In the rental analogy, the tenant (user) contacts the intermediary (proxy) to reach the landlord (foreign website) because direct contact is impossible.

Thus, a forward proxy is a "proxy server" that proxies the "client" to interact with the "target server".

When accessing the target server via a forward proxy, the target server does not know the real client’s identity and may even think the proxy itself is the client.

Uses of Forward Proxy

Bypassing access restrictions : Allows users to overcome IP-based access limits and reach foreign websites or educational networks.

Improving access speed : Proxy servers often have large disk buffers that cache responses; subsequent users can retrieve cached content quickly.

Hiding the client’s real IP : Users can conceal their IP address from the target server, reducing exposure to attacks.

Reverse Proxy

Reverse proxy (reverse proxy): A proxy server that accepts Internet connection requests, forwards them to internal servers, and returns the results to the Internet client, acting externally as a reverse proxy.

In the rental analogy, some houses can be rented directly from the landlord without an intermediary, representing direct access to domestic websites without a proxy.

Sometimes the party you think is the landlord may actually be a relative, friend, or sub‑landlord, analogous to a reverse proxy server.

In typical web development, a load‑balancing server (the sub‑landlord) receives client requests, forwards them to a real server (the landlord), and returns the result to the client.

Uses of Reverse Proxy

Hiding the server’s real IP : The client cannot see the actual server’s IP address.

Load balancing : Distributes client requests among multiple real servers based on their load.

Improving access speed : Provides caching for static content and high‑traffic dynamic content.

Security protection : Acts as an application‑level firewall, defending against web‑based attacks (e.g., DoS/DDoS), offering SSL termination, encryption, and HTTP authentication.

Differences Between Forward and Reverse Proxy

Although both sit between client and real server and forward requests/responses, they differ in purpose and deployment.

1. Forward proxy is a client‑side proxy that helps the client access resources it cannot reach directly; reverse proxy is a server‑side proxy that assists the server with load balancing and security.

2. Forward proxies are typically set up by the client on their own machine; reverse proxies are deployed by the server, often as part of a server cluster.

3. In forward proxy scenarios, the server does not know the true client identity; in reverse proxy scenarios, the client does not know the true server identity.

4. Forward proxies mainly solve access‑restriction problems, while reverse proxies provide load balancing, security, and speed improvements.

PS: The special format of this article is intended to make the knowledge easier to understand.

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