In a computer network, a reverse proxy server acts as a middleman – communicating with the users so the users never interact directly with the origin servers. Serving as a gateway, it sits in front of one or more web servers and forwards client (web browser) requests to those web servers. Web traffic must pass through it before they forward a request to a server to be fulfilled and then return the server’s response.

A reverse proxy is like a website’s ‘public face.’ Its address is the one advertised on the website. It sits at the edge of the site’s network to accept web browsers and mobile apps requests for the content hosted at the website. Reverse proxies make different servers and services appear as one single unit, allowing organizations to hide several different servers behind the same name – making it easier to remove services, upgrade them, add new ones, or roll them back. As a result, the site visitor only sees my-company-123.net and not myweirdinternalservername.my-company-123.net.

Reverse proxies help increase performance, reliability, and security. They provide load balancing for web applications and APIs. They can offload services from applications to improve performance through SSL acceleration, caching, and intelligent compression. By enforcing web application security, a reverse proxy also enables federated security services for multiple applications.

To sum up, reverse proxy servers can:

• Conceal the characteristics and existence of origin servers
• Ease out takedowns and malware removals
• Carry TLS acceleration hardware, letting them perform TLS encryption in place of secure websites
• Spread the load from incoming requests to each of the servers that supports its own application area
• Layer web servers with basic HTTP access authentication
• Work as web acceleration servers that can cache both dynamic and static content, thus reducing the load on origin servers
• Perform multivariate testing and A/B testing without inserting JavaScript into pages
• Compress content to optimize it and speed up loading times
• Serve clients with dynamically generated pages bit by bit even when they are produced at once, allowing the pages and the program that generates them to be closed, releasing server resources during the transfer time
• Assess incoming requests via a single public IP address, delivering them to multiple web-servers within the local area network

Simply because a forward proxy server sits in front of users, stopping origin servers from directly communicating with that user and a reverse proxy server sits in front of web servers, and intercepts requests. While a forward proxy acts for the client, guarding their privacy, a reverse proxy acts on behalf of the server. Forward proxies are used to capture traffic from managed endpoints; however, they don’t capture traffic from unmanaged endpoints like reverse proxies do.

Forward proxies are used not for load balancing, but for passing requests to the internet from private networks through a firewall and can act as cache servers to reduce outward traffic.

Yes and no! Technically, the only mode on a load balancer that is a real Reverse Proxy is Layer 7 mode. Whereas all Layer 4 load balancing modes such as NAT, DR and TUN are nothing like a reverse proxy. The clients are effectively talking directly (transparently) to the backend servers.

A reverse proxy is a layer 7 load balancer (or, vice versa) that operates at the highest level applicable and provides for deeper context on the Application Layer protocols such as HTTP. By using additional application awareness, a reverse proxy or layer 7 load balancer has the ability to make more complex and informed load balancing decisions on the content of the message – whether it’s to optimise and change the content (HTTP header manipulation, compression and encryption) and/or monitor the health of applications to ensure reliability and availability.

All modern load balancers are capable of doing both – layer 4 as well as layer 7 load balancing, by acting either as reverse proxies (layer 7 load balancers) or routers (layer 4 load balancers). An initial tier of layer 4 load balancers can distribute the inbound traffic across a second tier of layer 7 (proxy-based) load balancers. Splitting up the traffic allows the computationally complex work of the proxy load balancers to be spread across multiple nodes. Thus, the two-tiered model serves far greater volumes of traffic than would otherwise be possible and therefore, is a great option for load balancing object storage systems – the demand for which has significantly exploded in the recent years.

Security, load balancing, and ease of maintenance are the three most important benefits of using reverse proxy. Besides, they can also play a role in identity branding and optimization.

Improved online security

Reverse proxies play a key role in building a zero trust architecture for organizations – that secures sensitive business data and systems. They only forward requests that your organization wants to serve. If you’re only serving web content, you can configure your reverse proxy to exclude all requests other than those for ports 80 and 443 – the default ports responsible for HTTP and HTTPS. This helps divert traffic based on type.

Reverse proxies also make sure no information about your backend servers is visible outside your internal network, thus protecting them from being directly accessed by malicious clients to exploit any vulnerabilities. They safeguard your backend servers from distributed denial-of-service (DDoS) attacks – by rejecting or blacklisting traffic from particular client IP addresses, or limiting the number of connections accepted from each client.

For organizations looking at deploying proxy servers with extra teeth, reverse proxies can be easily upgraded to a firewall.

Increased scalability and flexibility

Increased scalability and flexibility, is generally most useful in a load balanced environment where the number of servers can be scaled up and down depending on the fluctuations in traffic volume. Because clients see only the reverse proxy’s IP address, the configuration of your backend infrastructure can be changed freely. When excessive amounts of internet traffic slow down systems, the load balancing technique distributes traffic over one or multiple servers to improve the overall performance. It also ensures that applications no longer have a single point of failure. If and when one server goes down, its siblings can take over!

Reverse proxies can use a technique called round-robin DNS to direct requests through a rotating list of internal servers. But if businesses have more demanding requirements, they can swap to a sophisticated setup that incorporates advanced load balancing features.

Web acceleration

Reverse proxies can also help with ‘web acceleration’ – reducing the time taken to generate a response and return it to the client.

Identity branding

Most businesses host their website’s content management system or shopping cart apps with an external service outside their own network. Instead of letting site visitors know that you’re sending them to a different URL for payment, businesses can conceal that detail using a reverse proxy.

Caching commonly-requested data

Businesses that serve a lot of static content like images and videos can set up a reverse proxy to cache some of that content. This kind of caching relieves pressure on the internal services, thus speeding up performance and improving user experience – especially for sites that feature dynamic content.

In theory yes, both Apache or NGINX can be used as reverse proxies. But if you are looking for a open source and free reverse proxy, our recommendation would be HAProxy. In our opinion the best reverse proxy out there, which is why it’s an integral part of our own ADC product offering.

What is HAProxy?

HAProxy is an open-source solution that provides high availability, load balancing, and proxying for TCP and HTTP-based applications. While it’s renowned for load balancing, it’s also a versatile tool for managing and routing web traffic effectively.

How Does it Work as a Reverse Proxy?

Leveraging HAProxy as a reverse proxy can markedly enhance the efficiency, scalability, and security of your web server configuration. This versatile tool enables the distribution of workloads across various servers, conceals the identities and attributes of your backend servers, and furnishes a unified interface for client requests.