What is a CDN?

A CDN (Content Delivery Network) is a network of servers spread across the world that stores and serves copies of your website content to visitors from the location closest to them. This makes your website faster, more reliable, and better able to handle high traffic.

Instead of every visitor fetching data from your main server (which is, for example, in Amsterdam), a visitor from Sydney fetches content from a CDN server in Australia. The distance the data has to travel is much shorter, resulting in faster load times.

CDNs are especially important for websites with international visitors, sites with many images or videos, and webshops where every second of load time impacts conversions. Large websites like Netflix, YouTube, and Shopify all use CDNs.

How does a CDN work?

A CDN consists of dozens to hundreds of servers (also called "edge servers" or "PoPs" - Points of Presence) spread across different continents. When you use a CDN, copies of your static content (images, CSS, JavaScript, videos) are stored on all these servers.

When someone visits your website, the CDN automatically detects where the visitor is located. A visitor from Berlin gets content from a server in Frankfurt, while a visitor from Tokyo gets content from a server in Japan. This happens completely automatically via DNS routing and Anycast network technology.

The first time someone requests a file, the CDN fetches it from your original server (the "origin server") and stores it locally in its cache. Next visitors from that same region then get the cached version, which is even faster. This is called "cache warming".

You can set how long files remain cached via cache headers. Images that never change can be cached for months, while your CSS needs to be redownloaded after each update. This happens via HTTP headers like "Cache-Control" and "Expires".

When you update content on your server, you often have to manually clear or "purge" the CDN cache. Most CDN providers offer a button or API to do this. Some advanced setups automatically detect when files change.

CDNs can also speed up dynamic content via techniques like connection optimization, HTTP/2, and edge computing. Some providers even offer edge functions - code that runs on the CDN servers themselves, even closer to the user.

Advantages of a CDN

Faster load times are the most direct benefit. Visitors worldwide experience better performance because content is served nearby. This can mean the difference between a 1 second and 5 second load time for international visitors.

Better SEO is an indirect benefit. Google uses page speed as a ranking factor. Faster websites rank better, especially since the "Core Web Vitals" update. A CDN can significantly improve your SEO scores.

Reduced server load means lower hosting costs. Because the CDN handles most requests, your own server has to do less work. This can mean you can get by with a smaller, cheaper VPS.

Higher reliability through redundancy is crucial. If your original server goes offline, the CDN can often continue serving cached content. Some CDNs have "Always Online" modes that can continue showing your entire cached site.

Protection against DDoS attacks is offered by many CDNs. Because your traffic goes through the CDN, they can filter malicious traffic before it reaches your server. This is valuable security that would otherwise require expensive specialist services.

Bandwidth savings can be considerable. You often pay less for CDN bandwidth than for server bandwidth. Moreover, CDNs often automatically compress files, which provides additional savings.

Better mobile experience because CDNs often optimize for mobile networks. Image optimization, compression, and protocol optimizations ensure your site loads quickly even on 4G networks.

Disadvantages of a CDN

Costs can add up, especially for small websites. Many CDN providers charge based on bandwidth. For a hobby site of €5 per month, a CDN of €10 per month can be disproportionately expensive. Fortunately, there are also free options like Cloudflare.

Complexity increases. You have to adjust DNS settings, understand cache configuration, and debugging becomes more difficult. Which version of your CSS is being served? The old cached version or the new one? This requires extra attention.

Cache invalidation problems are frustrating. You upload a new version of an image, but visitors still see the old version because the CDN has cached it. You have to purge the cache, which can take minutes to propagate.

Privacy considerations come into play. Your content is served via third-party servers. Some companies or government organizations object to data passing through American CDN providers due to privacy legislation.

Dependence on an external service is a risk. If the CDN fails (which is rare but not impossible), your entire website can become slow or go offline. In 2021, Fastly had a major outage that affected thousands of websites.

Certificate management becomes more complex with SSL/TLS. You also have to configure your SSL certificate on the CDN. Some CDNs offer free SSL, but this requires additional setup and renewal.

Not all content benefits equally. For small websites with only local visitors, a CDN has little added value. The extra complexity and costs then don't outweigh the minimal speed gain.

Who is a CDN suitable for?

International websites with visitors from multiple continents benefit most from a CDN. A Dutch company with customers in Asia, America, and Europe sees dramatic improvements in load times for distant visitors.

E-commerce sites should really always use a CDN. Every second faster load time can increase conversions by percentages. Visitors have little patience when shopping online - a slow checkout directly costs revenue.

Content-heavy websites with many images, videos, or downloads benefit enormously. A photography portfolio, streaming platform, or software download site can drastically reduce bandwidth costs with a CDN.

News and media sites that can suddenly get viral traffic need a CDN for protection. If your article goes trending on social media, tens of thousands of visitors can come simultaneously. A CDN prevents your server from crashing.

SaaS applications with users worldwide want to offer a consistent, fast experience. A project management tool or CRM used in different time zones must respond quickly everywhere.

WordPress websites, especially with many plugins and themes, often become faster with a CDN. WordPress can be resource-intensive - a CDN reduces the load on your server.

Practical tips for CDN use

Start with Cloudflare if you want a budget CDN. Their free plan offers CDN, SSL, and basic DDoS protection. It's perfect for getting acquainted with CDNs without financial risk. Upgrading can always happen later if you need more features.

Configure your cache headers correctly. Use long cache times for static assets (images, fonts, libraries) and short times for HTML. A good setup: 1 year for images, 1 week for CSS/JS, no cache for HTML.

Implement cache busting for CSS and JavaScript. Use version numbers in filenames (style.v123.css) or query strings (style.css?v=123). When you make an update, you change the version number and browsers automatically load the new version.

Test your site thoroughly after CDN implementation. Check if all images load, CSS works correctly, and JavaScript functions as expected. Sometimes relative URLs break or mixed content warnings (HTTP content on HTTPS page) become visible.

Monitor your CDN performance. Most providers offer analytics: how much traffic, cache hit ratio, bandwidth saved. This shows the value of your CDN and helps with optimizations.

Use image optimization features if your CDN offers them. Cloudflare Polish, AWS CloudFront with image processing, or KeyCDN's image optimization can automatically compress images and serve the right format (WebP, AVIF).

Consider edge caching for APIs in high-traffic applications. Some API responses (e.g., product catalogs) don't change often and can be cached. This reduces database queries and speeds up your application.

Set up security rules. Many CDNs offer Web Application Firewall (WAF) functionality. Block known threats, rate limit aggressive bots, and protect against common attacks like SQL injection.

Use geographic restrictions if relevant. Do you only sell in Europe? Then block traffic from other regions to reduce scraping and attacks. This can also help with GDPR compliance.

Purge selectively, not always everything. Many CDNs let you purge specific URLs or patterns. If you update one blog post, only purge that page, not your entire cache. This keeps performance high for other visitors.

Combine with server-side caching. A CDN doesn't replace server-side caching (like Redis, Varnish, or WordPress caching plugins). Use both for optimal performance.

Read the documentation of your CDN provider. Each provider has its own features and best practices. Cloudflare works differently than AWS CloudFront, which is different again from Bunny CDN. Invest time in understanding.

Compare CDN providers on price, locations, and features. Look at the number of PoPs and where they're located (important for your target audience), pricing models (per GB, per request, or flat fee), and extra features like DDoS protection or image optimization.

Frequently Asked Questions

How much does web hosting cost on average?

Web hosting costs between €3 and €15 per month for shared hosting on average. VPS hosting starts around €10-€20 per month, and dedicated servers from €50 per month.

Can I upgrade to a different package later?

Yes, with most hosting providers you can easily upgrade to a larger package when your website grows. This can usually be done without downtime.

Is Dutch hosting better than foreign hosting?

For Dutch visitors, Dutch hosting is often faster due to the shorter distance. Additionally, communication with support is easier and you comply with GDPR legislation.