What is CDN?
Content Delivery Network
TL;DR
A CDN (Content Delivery Network) is a network of servers around the world that delivers website content from the location closest to each user.
Example
Without CDN: Your server is in Oslo. User in Sydney requests image. Image travels 15,000 km. Takes 200ms.
With CDN: CDN has server in Sydney. User in Sydney requests image. Image travels 50 km. Takes 20ms.
What CDNs cache:
- Images and videos
- CSS and JavaScript files
- Fonts
- HTML pages (sometimes)
- API responses (sometimes)
Popular CDNs:
| CDN | Notes |
|---|---|
| Cloudflare | Popular, free tier |
| AWS CloudFront | AWS ecosystem |
| Fastly | Edge computing |
| Bunny.net | Affordable |
| Vercel/Netlify | Built-in for their hosting |
Explanation
How CDNs Work
- First user requests file
- CDN fetches from origin server
- CDN stores copy at edge location
- Next user in same region gets cached copy
- Much faster delivery
Edge locations: CDN servers placed around the world. "Edge" means close to end users. Major cities have edge servers.
CDN Benefits
Speed: Faster loading for global users Reliability: If one server fails, others take over Security: DDoS protection, SSL termination Bandwidth savings: Origin server handles less traffic SEO: Faster sites rank better
Why It Matters
For Business Owners
CDNs make your site faster globally. If you have international customers, CDN dramatically improves their experience.
CDNs improve reliability. Your origin server can go down, but CDN keeps serving cached content.
CDNs handle traffic spikes. Viral content? Product launch? CDN distributes load across many servers.
CDNs are often affordable. Many have free tiers. Costs scale with usage.
Do You Need a CDN?
Yes if:
- Users in multiple countries
- Heavy traffic expected
- Many images or videos
- Performance is critical
Maybe not if:
- Local business only
- Very low traffic
- Simple static site (hosting may include CDN)
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