Content Delivery Networks (CDNs): Guide to Faster Websites
Content Delivery Networks (CDNs): Guide to Faster Websites
Published on April 23, 2025 Last Updated on June 27, 2025
Written by
Morgan Frank - Specialist in Page Speed
Key Takeaways
A CDN is a network of servers distributed around the world that store copies of
your website’s content.
CDNs significantly reduce latency and improve page speed, especially for users
geographically far from your origin server.
CDNs also increase availability, reduce bandwidth costs, and can improve SEO.
CDNs work by routing user requests to the closest server.
Choose a CDN based on global coverage, performance, features, pricing, ease of
use, and support.
Imagine your website’s files are like packages that need to be delivered to users around the world. Without a CDN, all those packages ship from a single warehouse (your origin server).
A CDN is like having a network of distribution centers strategically placed around the globe, so packages can be shipped from the closest location, drastically reducing delivery time.
A Content Delivery Network (CDN), then, is a geographically distributed network of servers that work together to provide fast delivery of internet content. This content includes everything from images and videos to CSS and JavaScript files – all the static assets that make up your website.
Why Use a CDN?
Reduced Latency: This is the main benefit. Latency is the time it takes for data to travel between the server and the user’s browser. The closer the server, the lower the latency, and the faster the page loads.
Improved Page Speed: Reduced latency directly translates to faster page load times, especially for users who are geographically far from your origin server (the server where your website is hosted).
Increased Availability and Redundancy: If one CDN server goes down, another server in the network can take over, ensuring your website remains available. This is like having multiple pizzerias – if one is closed, you can order from another.
Reduced Bandwidth Costs: By serving content from CDN servers, you reduce the load on your origin server, which can save you money on bandwidth costs.
Improved SEO: Page speed is a ranking factor for search engines, and CDNs can significantly improve your website’s speed.
Handling Traffic Spikes: CDNs are designed to handle large amounts of traffic. They can absorb traffic spikes (e.g., during a viral marketing campaign) without slowing down your website.
Security: Most of the CDNs offer security features such as DDoS protection.
How CDNs Work
Origin Server: Your website is hosted on an origin server (your regular web hosting).
CDN Caching: You configure your website to use a CDN. The CDN pulls your website’s static content (images, CSS, JavaScript, etc.) from your origin server and stores copies on its servers around the world. This is called caching.
User Request: When a user visits your website, their browser sends a request.
CDN Routing: The CDN’s DNS (Domain Name System) servers intelligently route the user’s request to the closest CDN server (based on the user’s IP address).
Content Delivery: The closest CDN server serves the requested content to the user’s browser.
Cache Updates: The CDN periodically checks your origin server for updates to your content. If it finds changes, it updates its cached copies.
Key Concepts Related to CDNs
Points of Presence (PoPs): These are the physical locations of the CDN servers around the world. A CDN with more PoPs in more locations generally provides better coverage and performance.
Edge Servers: The servers within the PoPs that actually serve the content to users are called edge servers.
Caching Policies: CDNs allow you to configure caching policies, which determine how long files are stored in the cache and how often the CDN checks for updates from your origin server. This is often done using the same HTTP caching headers we discussed in the “Browser Caching” section (e.g., Cache-Control, Expires).
Purging/Invalidating the Cache: If you update a file on your origin server, you may need to purge or invalidate the cached copy on the CDN so that users get the latest version. Most CDNs provide tools for doing this.
Origin Shield: Some CDNs offer an “origin shield” – an extra layer of caching between the edge servers and your origin server. This further reduces the load on your origin server.
Choosing a CDN
Many CDN providers are available, each with different features, pricing, and global coverage. Some popular options include:
Cloudflare: A very popular CDN with a generous free plan. It also offers security features like DDoS protection and a Web Application Firewall (WAF).
Amazon CloudFront: Amazon’s CDN, tightly integrated with other AWS services.
Fastly: Known for its real-time caching and purging capabilities.
Akamai: One of the oldest and largest CDN providers, with a vast global network.
Google Cloud CDN: Google’s CDN, integrated with Google Cloud Platform.
Bunny CDN: A performance-focused CDN with competitive pricing.
KeyCDN: Another one.
StackPath: CDN Provider.
When choosing a CDN, consider:
Global Coverage: Does the CDN have PoPs in locations that are relevant to your target audience?
Performance: How fast is the CDN? Look for benchmarks and reviews.
Features: Does the CDN offer the features you need (e.g., caching policies, origin shield, security features)?
Pricing: How much does the CDN cost? Pricing models vary (e.g., pay-as-you-go, monthly plans).
Ease of Use: How easy is it to set up and configure the CDN?
Support: Does the CDN provider offer good customer support?
Conclusion
A Content Delivery Network (CDN) is an essential tool for any website that wants to deliver a fast and reliable experience to users around the world. It’s a relatively simple and cost-effective way to dramatically improve page speed, reduce server load, and enhance your website’s overall performance. If you’re not already using a CDN, it’s one of the most impactful optimizations you can make.
Determined to change that, he built RapidLoad — a smart, AI-driven tool that empowers site owners to dramatically improve speed scores, enhance user experience, and meet Google’s Core Web Vitals without needing to touch a single line of code.
