CDN – What is a Content Delivery Network?

What is a CDN

A content delivery network (CDN) is a collection of servers that work together to accelerate the delivery of web pages and high-load applications. When a user accesses a website, the data is typically retrieved from a server that may be far away, resulting in slow download times for large files. CDN servers are placed in various locations around the world to reduce the distance that data must travel, ensuring that website content is delivered much faster.

CDN servers also act as intermediaries, managing some of the data transfers between clients and servers. This reduces network traffic on web servers, increases bandwidth, and improves the overall performance of applications. In addition to these benefits, CDN improves fault tolerance, scalability, and the ability to promote websites in search results.

By introducing intermediate links in the form of caching sites, a CDN reduces the distance between consumers and information nodes, resulting in faster response times, even for resource-intensive content.

As fast information access has become the norm, the speed of loading pages, continuous playback of streaming media, and installation and updating of game services are all critical to user behavior, conversions, and audience growth.

A slow-loading web page leads to lower rankings in search results and a higher number of bounces, which can cause a potential client or user to go to a competitor. Using CDN can avoid these issues, enabling faster download times and improving overall user experience.

The Infrastructure of a CDN

The infrastructure behind a CDN is composed of a network of geographically distributed servers that work together to deliver web content to users as quickly as possible. These servers, also known as nodes, are strategically located in data centers around the world, often in major cities and near internet exchange points, to ensure that the data reaches the user with minimal latency.

Each node in a CDN is responsible for caching and delivering content to users located in its region. When a user requests a file, the request is first routed to the nearest node, which then searches its cache for the requested file.

If the file is not found in the cache, the node retrieves it from the origin server and caches it for future requests. This ensures that subsequent requests for the same file can be delivered faster from the cache without needing to fetch it again from the origin server.

What is a Content Delivery Network

The infrastructure of a CDN is designed to be fault-tolerant and scalable, with redundancy built into every level of the system. In many cases, CDNs operate with hundreds or even thousands of nodes distributed around the world, allowing them to serve large amounts of traffic with low latency. Additionally, most CDNs have load-balancing and failover mechanisms in place to ensure that traffic is automatically routed to the most available and efficient nodes in the network.

The backbone of a CDN is its routing and caching technologies, which enable it to distribute and manage content as efficiently as possible. These technologies include advanced DNS routing, server load balancing, edge caching, and content optimization techniques that work together to deliver web content to users with speed and reliability. All of this infrastructure is maintained and operated by the CDN provider, freeing up the content provider to focus on creating and publishing their content.

What are the advantages of a CDN?

A content delivery network has several advantages that make it an attractive option for organizations looking to improve their web performance and user experience.

Here are some of the main benefits of using a CDN:

  • Improved website speed and performance: By caching web content on servers located closer to users, a CDN reduces the distance that data needs to travel, improving the speed and performance of websites and applications. This can lead to faster page load times, reduced bounce rates, and higher engagement from users.
  • Increased availability and reliability: A CDN's distributed infrastructure provides increased redundancy and fault tolerance, ensuring that web content remains available even during high traffic spikes, server failures, or network outages. This can help improve website uptime and reduce the risk of website downtime or performance issues.
  • Reduced server load and bandwidth usage: By offloading the delivery of web content to a CDN, a website's origin server experiences less load and bandwidth usage, freeing up resources to handle other tasks. This can improve website scalability, reduce infrastructure costs, and improve reliability.
  • Better user experience: A faster, more reliable website can improve overall user experience, reducing frustration and improving engagement. This can lead to increased conversions, sales, and customer loyalty.
  • Global reach: CDNs have a distributed infrastructure that can deliver content to users worldwide, improving the user experience for global audiences. This can help improve website engagement, increase conversions, and reach new audiences in different regions.
  • Improved security: Many CDNs offer security features such as SSL encryption, DDoS protection, and web application firewalls that can help protect websites and applications from malicious attacks. This can help improve website security and reduce the risk of data breaches or cyber-attacks.

In summary, CDNs offer several benefits that can help improve website performance, reliability, and security, while also improving the user experience and reducing infrastructure costs. By offloading the delivery of web content to a distributed network of servers, organizations can improve website speed, scalability, and availability, while also improving the security and resilience of their websites and applications.

Most hosting providers (be it something like VPS or even cheap ones) tend to provide CDN services out of the box, either through a third-party provider or through their own network.

What types of content can a CDN deliver?

A content delivery network can deliver a wide range of content types, including static and dynamic content, as well as video and audio streaming.

Here are some examples of the types of content that a CDN can deliver:

  • Static content: This includes files such as HTML, CSS, JavaScript, and image files that are served to users as-is without any server-side processing. By caching static content on a CDN, website owners can improve website speed and reduce server load.
  • Dynamic content: This includes content that is generated on the fly by a web server in response to user requests, such as personalized content, e-commerce pages, and social media feeds. A CDN can deliver dynamic content by routing requests to the nearest server and caching the response for subsequent requests.
  • Video and audio streaming: A CDN can also deliver streaming media content, such as live and on-demand video and audio streams. Using adaptive bitrate streaming, a CDN can deliver high-quality video and audio to users with varying network conditions, adjusting the bitrate in real time based on the user's available bandwidth.
  • Software downloads: CDNs can also be used to deliver large files such as software updates, patches, and game downloads. A CDN can reduce download times and improve the user experience by caching these files on servers closer to users.
  • APIs and other web services: CDNs can also deliver APIs and other web services, such as location-based services, weather APIs, and financial data feeds. By caching API responses on a CDN, website owners can improve the performance of their applications and reduce server load.

In summary, a CDN can deliver a wide range of content types, from static and dynamic content to video and audio streaming, software downloads, and web services.

What are some well-known CDN providers?

With hundreds of CDN providers to choose from, it can be challenging to determine which one is the right fit for your business. That's why we're going to dive into some of the most popular and well-known providers in this section.

These are brands/providers that almost everyone will have heard of before, so we'll focus strictly on the key benefits and features of each platform.

1. Cloudflare


Cloudflare is a global cloud service built on a network of servers that offers speed, security, and privacy to clients. With coverage in over 100 countries and direct connections to over 11,000 networks, including hosting providers and large enterprises, Cloudflare is a popular choice among webmasters, especially since it offers a free plan.

The platform offers a range of website and application performance services, including a CDN for fast static and dynamic content delivery, reliable DNS, smart routing, load balancing, and web optimization. Other services include analytics, detailed logs, and tools to manage and monitor application infrastructure.

Cloudflare also offers features to address challenges affecting performance, such as heavy, complex web pages, interactivity and personalization, and globally distributed visitors.

2. StackPath


StackPath is a leading edge cloud platform that offers an array of solutions, such as a content delivery network, web application firewall (WAF), and edge computing services to accelerate the delivery of digital content and applications while enhancing their security. The company has a global network of over 40 data centers and over 70 points of presence, which provide unparalleled delivery speed and uptime for online content.

With StackPath's advanced edge computing capabilities, developers can build and deploy their applications at the edge, providing real-time data processing and reduced latency for end-users. StackPath's WAF offers comprehensive protection against a variety of web threats, such as OWASP Top 10 vulnerabilities, DDoS attacks, and malicious bots. Additionally, StackPath's CDN offers fast and reliable delivery of digital content, providing a seamless user experience.

StackPath is also the CDN provider that WP Rocket (a WordPress performance plugin I use on Stack Diary) uses if you sign up for their CDN feature. And I can personally vouch for the network's reliability.

3. Google Cloud CDN

Google Cloud CDN

One of the key benefits of Google Cloud CDN is its integration with other Google Cloud services, such as Google Compute Engine and Google Kubernetes Engine. This allows for easy setup and management of the CDN, as well as automatic scaling, to handle increases in traffic. Additionally, Google Cloud CDN supports both HTTP and HTTPS traffic with automatic SSL certificate management.

Google Cloud CDN also offers a variety of features to help optimize content delivery, such as edge caching, content-based routing, and advanced caching policies. These features allow website owners to customize how their content is cached and delivered to users, helping to improve performance further and reduce latency.

How to choose a CDN provider that's right for you?

When choosing a content delivery network provider, there are several key factors you should consider.

Here is a checklist of some of the most important things to look for:

  • Network size and coverage: Does the CDN provider have a large network of geographically distributed servers to provide broad coverage? The more servers a CDN has, the better it can handle high traffic loads and reduce latency.
  • Performance and speed: TCP acceleration, route optimization, and content compression to improve performance.
  • Security features: SSL/TLS encryption, DDoS protection, web application firewalls, and other security tools to protect your website from cyber threats.
  • Customization and flexibility: Pay attention to customization options, such as caching settings, API integrations, and bandwidth controls. This will allow you to tailor the CDN to your specific needs and optimize your website's performance.
  • Analytics and reporting: Detailed analytics and reporting tools to help you track website performance, user behavior, and other key metrics. This information can help you optimize your website and improve the user experience.
  • Technical support and customer service: Ensure that the CDN provider offers responsive technical support and customer service, with knowledgeable support staff who can help you resolve any issues or answer any questions you may have.
  • Pricing and contract terms: Finally, look for a provider that offers transparent pricing and flexible contract terms. Compare pricing and features across different providers to find the best value for your business.

By evaluating potential providers based on these criteria, you can choose the right CDN for your organization and ensure that your website delivers fast, reliable content to your users.

Usage Statistics: how popular are CDNs?

Even though it is quite difficult to accurately track the exact usage of CDN providers across the board, we can examine the CDN section from the 2022 Web Almanac report to get a general idea.

Here are some key statistics from the said report:

  • For the last three years, there has been a steady increase - 5% yearly - in the number of content businesses/websites serve over a CDN.
  • For HTML content, 71% of requests are from the origin and 29% from CDNs. For subdomain content, 53% origin and 47% CDN. And for third-party content, 33% origin and 67% CDN.
  • In the top 1,000 sites worldwide, more than 64% are utilizing a content delivery network. That number stays the same throughout the top 10,000 list but declines to 52% in the top 100,000 list.
  • The most popular type of content served over a CDN remains images and audio.

The technical aspect of implementing a CDN service in an existing project has also gone down tremendously. In other words, it is easier than ever to implement a CDN on your own website, be it through a third-party solution (such as a WordPress plugin) or by editing DNS records (which is a service Cloudflare offers).