What Is a Reverse Proxy?

What Is a Reverse Proxy? A Simple Definition

A reverse proxy is a server that sits in front of one or more backend servers and forwards client requests to the appropriate backend. Instead of clients connecting directly to your application servers, they connect to the reverse proxy, which then routes traffic, handles encryption, balances load, and caches responses.

A reverse proxy is the front desk of a building. Visitors check in and get directed to the right office. They never see the floor plan. The reverse proxy knows which backend server handles each request and shields the internal layout from outsiders.

How a Reverse Proxy Works (Step by Step)

1. Client sends a request — A browser, mobile app, or API client makes an HTTP request to your domain (e.g. https://api.yourservice.com/data).
2. DNS routes to the reverse proxy — Your domain’s DNS records point to the reverse proxy, not your application servers. The proxy is the only server exposed to the public internet.
3. Proxy inspects the request — It checks the URL path, Host header, and other request attributes against its routing rules to decide which backend should handle it.
4. Proxy applies policies — Rate limiting, authentication, IP allow/block lists, and request filtering happen here before the request ever reaches your application.
5. Request forwarded to backend — The proxy opens a connection to the chosen backend server and passes the (potentially modified) request through.
6. Response flows back through the proxy — The backend responds. The proxy may cache the response, compress it, or modify headers before returning it to the client.

Forward Proxy vs Reverse Proxy: The Key Difference

A forward proxy sits in front of clients (like your browser or an AI agent) and routes their requests to the internet. It hides the client’s IP address from destination servers. When you use ProxyBase, you’re using a forward proxy — your requests go through a residential IP before reaching the target website.

A reverse proxy sits in front of one or more servers and routes incoming client requests to the right backend. It hides the backend servers’ details from clients. Popular reverse proxies include Nginx, HAProxy, Cloudflare, and AWS Application Load Balancer.

The direction is the difference: forward proxies protect clients (you), while reverse proxies protect servers (your infrastructure). Many real-world setups use both — forward proxies for outbound anonymity, reverse proxies for inbound traffic management.

What Reverse Proxies Do

• Load balancing: Distribute incoming traffic across multiple backend servers so no single server gets overwhelmed. Common algorithms include round-robin, least connections, and IP hash. If one server goes down, the reverse proxy routes around it automatically — this is called failover or high availability.
• SSL termination: Handle HTTPS encryption and decryption at the proxy layer so backend servers can focus on application logic. This simplifies certificate management — install the cert once on the reverse proxy, not on every server. It also offloads CPU-intensive TLS handshakes from your application servers.
• Caching: Store copies of frequently requested responses and serve them directly from the proxy, reducing load on backend servers and speeding up response times for users. A reverse proxy can cache static assets (images, CSS, JS), API responses, or entire HTML pages. This is what CDNs like Cloudflare do at global scale.
• Security: Act as a shield between the public internet and your application servers. Filter malicious requests, block DDoS attacks, hide internal server architecture (IPs, software versions, open ports), and enforce IP allow/block lists. If an attacker can’t see your origin server, they can’t directly attack it.
• Compression: Compress responses (gzip, brotli) before sending them to clients, reducing bandwidth costs and page load times. A reverse proxy can compress once and serve the compressed version from cache.
• Request routing: Route requests to different backends based on URL path, hostname, or headers. For example: /api/* goes to your API servers, /blog/* goes to your CMS, and /app/* goes to your web app. This is sometimes called a layer 7 proxy or content-based routing.

Common Reverse Proxy Software

• Nginx — The most widely deployed reverse proxy on the internet. Handles static file serving, reverse proxying, load balancing, and SSL termination in a single lightweight process. Powers ~34% of all websites. Learn more in our what is a proxy guide.
• HAProxy — Purpose-built for high-availability load balancing. Common in large-scale microservice deployments where sub-millisecond proxy latency matters.
• Cloudflare — A global reverse proxy and CDN. Sits between your domain and visitors, absorbing DDoS attacks, caching content at edge locations worldwide, and filtering bot traffic before it reaches your origin.
• AWS ALB / API Gateway — Managed reverse proxies in AWS. ALB handles layer 7 HTTP routing; API Gateway adds API key management, usage plans, and request transformation for REST and WebSocket APIs.
• Envoy — A modern L7 proxy designed for service meshes (Istio, Consul). Built for dynamic, cloud-native environments where backend servers come and go constantly.
• Caddy — A newer reverse proxy that automatically obtains and renews TLS certificates via Let’s Encrypt. Simpler configuration than Nginx, good for smaller deployments.

Reverse Proxy Example: A Minimal Nginx Setup

Here is what a minimal reverse proxy configuration looks like. This Nginxserver block accepts traffic for example.com, terminates TLS, and forwards every request to a backend application listening on localhost:3000:

server {
    listen 443 ssl;
    server_name example.com;

    ssl_certificate     /etc/letsencrypt/live/example.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;

    location / {
        proxy_pass http://127.0.0.1:3000;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
}

The proxy_pass directive is the entire reverse proxy in one line: clients talk to Nginx, Nginx talks to your app. Add more location blocks to route /api/* to one backend and /static/* to another. Add an upstream block with multiple servers to get load balancing:

upstream app_servers {
    server 10.0.0.1:3000;
    server 10.0.0.2:3000;
    server 10.0.0.3:3000;
}

server {
    location / {
        proxy_pass http://app_servers;
    }
}

Reverse Proxy vs Load Balancer vs API Gateway

These terms overlap, but they’re not the same thing:

• Reverse Proxy — The broadest category. Any server that accepts client requests and forwards them to backends. Nginx and Apache (with mod_proxy) are reverse proxies.
• Load Balancer — A specific use of reverse proxying where the primary goal is distributing traffic across multiple identical backend servers. HAProxy and AWS ALB are purpose-built load balancers. Every load balancer is a reverse proxy, but not every reverse proxy is a load balancer.
• API Gateway — A reverse proxy specialized for API traffic. Adds API-specific features: authentication, rate limiting per API key, request/response transformation, and routing based on API version or path. AWS API Gateway and Kong are examples. An API gateway is a reverse proxy with API management layered on top.

Reverse Proxies and Bot Detection

If you’re building web scrapers or AI agents, reverse proxies matter to you for a different reason: they’re often what runs bot detection. When you hit a target website, the first thing your request encounters is usually a reverse proxy — Cloudflare, Akamai, AWS CloudFront, or a custom Nginx/Envoy deployment. These proxies inspect incoming requests for signs of automation: unusual headers, TLS fingerprints, IP reputation, request patterns.

This is why using clean residential proxies matters. If a reverse proxy sees your request coming from a known datacenter IP range with a mismatched TLS fingerprint, it blocks you before you ever reach the application. A residential IP from a provider like ProxyBase makes your traffic look like a regular home broadband user — significantly reducing the chance the target’s reverse proxy flags you. Learn more about how this works in our guide on why AI agents need proxies.

When Forward and Reverse Proxies Work Together

In a scraping or AI agent pipeline, you chain both:

Your Agent → Forward Proxy (ProxyBase residential IP) → Internet → Reverse Proxy (Cloudflare/Nginx) → Target Website

The forward proxy hides who you are. The reverse proxy is what you’re hitting — it’s how the target website serves traffic, and it’s often the thing running bot detection. If you build scraping or AI agent infrastructure, you need to understand both.

Reverse Proxy FAQ