Proxies vs. Reverse Proxies: What's the Difference?

In software architecture, the term "proxy" gets thrown around a lot. At its core, a proxy is simply an intermediary—a server that acts on behalf of another computer. Think of it as a middle-person handling requests and responses.

But the direction it faces changes everything. Is it working for the client (you) or for the server (the website)? This distinction is the key to understanding the difference between a forward proxy and a reverse proxy.

Let's untangle it.

The Forward Proxy: The Client's Butler

A forward proxy sits in front of a client or a group of clients (like users on a corporate network) and forwards their requests out to the internet. The destination server (e.g., google.com) only ever sees the proxy's IP address, not the original client's.

You've probably used or heard of a forward proxy without realizing it. They are primarily used for:

1. Anonymity & Privacy: It hides your IP address, making your browsing activity more private. This is the basic principle behind many VPNs.
2. Bypassing Restrictions: If a website is blocked in your country, you can use a forward proxy in another country to access it.
3. Security & Filtering: A company can use a forward proxy to block employees from accessing certain sites (like social media) or to scan outgoing traffic for malware.
4. Caching: If many users on a network request the same resource, the proxy can cache it and serve it directly, saving bandwidth and speeding up access.

Think of a forward proxy as a personal shopper. You tell the shopper what you want, and they go to the store, buy it, and bring it back to you. The store only knows it dealt with the shopper, not with you.

The Reverse Proxy: The Server's Bodyguard

A reverse proxy does the opposite. It sits in front of one or more web servers and intercepts all incoming requests from the internet. To the outside world, the reverse proxy is the web server. It decides which internal server should handle the request and forwards it accordingly.

This is incredibly common in modern web architecture. Major websites like Netflix and Airbnb rely heavily on them. Why?

1. Load Balancing: This is the big one. A reverse proxy can distribute incoming traffic across a pool of backend servers. This ensures high availability and scalability.
2. Security: Since the backend servers' IP addresses are hidden, it's harder for attackers to target them directly. The reverse proxy can also act as a Web Application Firewall (WAF) to block malicious requests.
3. SSL/TLS Termination: It takes on the job of encrypting and decrypting traffic so your servers don't have to. If you're new to this term, the next section has you covered.
4. Caching & Compression: It can cache static content (like images or CSS) to serve them faster and compress outbound data to reduce latency.
5. Routing / URL Rewriting: In a microservices architecture, it can route api.example.com/users to the user service and api.example.com/products to the product service.

Think of a reverse proxy as a company's main receptionist. You call the main company number, and the receptionist routes your call to the right person. You don't need to know the direct extension of every employee.

A Quick Detour: What is SSL/TLS Termination?

You saw "SSL/TLS Termination" listed as a key feature. Let's break that down.

First, a quick history lesson. SSL (Secure Sockets Layer) is the old, deprecated protocol for encrypting web traffic. It has been replaced by the modern, more secure TLS (Transport Layer Security). However, the term "SSL" has stuck around, and people often use it when they really mean TLS. Both are the technologies that power HTTPS. (If you want a deeper dive, you can read my post on HTTPS here.)

SSL/TLS termination is the process where the reverse proxy terminates (i.e., ends) the encrypted connection from the client.

The flow looks like this:

1. A user's browser connects to your website, creating an encrypted HTTPS connection with the reverse proxy.
2. The reverse proxy decrypts all the incoming traffic.
3. The proxy then sends the now-unencrypted HTTP traffic to the correct backend server over a secure internal network.

This is a huge win because:

• It simplifies certificate management. You only need to install and renew your TLS certificate on the proxy, not on every single backend server.
• It allows for traffic inspection. Since the traffic is decrypted at the proxy, a Web Application Firewall (WAF) can inspect it for security threats before it ever reaches your application.

How They Work Together

It's entirely possible for a single request to pass through both types of proxies.

Your Laptop ➡️ Corporate Forward Proxy ➡️ Internet ➡️ Website's Reverse Proxy & Load Balancer ➡️ Backend Web Server

The main difference is ownership. A forward proxy is managed by the client or their network administrator. A reverse proxy is managed by the server's administrator.

The Takeaway

Understanding proxies isn't just academic—it's fundamental to building secure, scalable, and resilient applications.

• Forward Proxy: Works for the client. Provides anonymity, filtering, and caching for outgoing traffic.
• Reverse Proxy: Works for the server. Provides load balancing, security, and performance boosts for incoming traffic.

Next time you hear "we're putting it behind a proxy," you'll know exactly what questions to ask: which kind, and what for?

sam