Amazon CloudFront – The Complete Guide to the AWS CDN (2026)

Amazon CloudFront is AWS's global content delivery network (CDN). It caches your content at hundreds of edge locations around the world, so that when a user requests a file, it's served from a location physically near them rather than from your origin server thousands of miles away. The result is dramatically lower latency for users, less load on your backend, and often a lower bill, since edge delivery is cheaper than serving everything directly from S3 or EC2.

But CloudFront is more than a cache. It terminates HTTPS with free certificates, integrates with AWS's security services to block attacks, can run code at the edge for personalization and routing, and protects your origin from direct exposure. For any website or API with a geographically spread audience, it's one of the highest-impact services you can add.

This guide explains how CloudFront works, its core building blocks, how to serve content securely from S3, caching and invalidation, security features, edge compute, and the pricing model.

What Is a CDN, and How Does CloudFront Work?

When a user requests content through CloudFront, the request is routed to the nearest edge location. If that edge already has a cached copy (a cache hit), it returns it immediately. If not (a cache miss), CloudFront fetches the content from your origin, stores it at the edge according to your caching rules, and serves it — so subsequent requests in that region are fast. This simple mechanism is what turns a slow, far-away server into a snappy global experience.

Distributions, Origins, and Behaviors

• Distribution — the top-level CloudFront configuration, with its own domain name (and optionally your custom domain).
• Origin — where CloudFront fetches content from: an S3 bucket, an Application Load Balancer, an API Gateway, or any custom HTTP server.
• Cache behaviors — rules that map URL path patterns to origins and caching settings, so you can, for example, cache /images/* aggressively while passing /api/* straight through with no caching.

Serving S3 Securely with Origin Access Control

The most common CloudFront setup is a fast, HTTPS static site or asset store backed by S3. The right way to do it keeps the bucket private:

1. Upload your site or assets to an S3 bucket (Block Public Access stays on).
2. Create a CloudFront distribution with that bucket as the origin.
3. Attach an Origin Access Control (OAC) so only CloudFront — not the public internet — can read the bucket.
4. Add an ACM certificate for HTTPS and point your domain (via Route 53) at the distribution.

# Minimal distribution pointing at an S3 origin
aws cloudfront create-distribution \
  --origin-domain-name my-site-bucket.s3.amazonaws.com \
  --default-root-object index.html

Caching, TTLs, and Invalidations

How long CloudFront keeps a copy is governed by TTLs (time to live), set via cache policies or your origin's Cache-Control headers. Cache static, versioned assets for a long time and dynamic content briefly or not at all. When you deploy new files that reuse old names, issue an invalidation (e.g. /index.html or /*) so edges fetch the fresh version. A common best practice is to use versioned filenames (like app.abc123.js) so you rarely need invalidations at all.

Security Features

• HTTPS everywhere — free TLS certificates via AWS Certificate Manager; redirect HTTP to HTTPS at the distribution.
• AWS WAF — filter malicious requests (SQL injection, bad bots) at the edge.
• AWS Shield — built-in DDoS protection (Shield Standard is automatic and free).
• Signed URLs and signed cookies — grant time-limited access to private content (paid videos, downloads).
• Geo-restriction — allow or block access by country.

Edge Compute: CloudFront Functions and Lambda@Edge

You can run code at the edge to customize requests and responses. CloudFront Functions are lightweight, ultra-fast JavaScript for simple tasks like header manipulation, redirects, or URL rewrites. Lambda@Edge runs full Lambda functions at the edge for heavier logic such as authentication, A/B testing, or generating responses — bringing computation close to users for lower latency.

Real-World Use Cases

• Serving static websites and single-page apps globally and cheaply.
• Delivering images, CSS/JS, and downloads with low latency.
• Streaming video on demand and live content.
• Accelerating and protecting dynamic web apps and APIs.
• Reducing S3/EC2 data-transfer costs by caching at the edge.

Pricing Model (in detail)

You pay primarily for data transferred out to viewers and the number of HTTP/HTTPS requests, both priced by geographic region (price classes let you limit to cheaper regions). Invalidations are free for the first 1,000 paths per month. CloudFront egress is generally cheaper than serving directly from S3 or EC2, and the Free Tier includes 1 TB of data transfer out and 10 million requests per month.

Common Mistakes to Avoid

• Leaving the S3 bucket public — use OAC and keep the bucket private.
• Poor cache settings — caching dynamic content too long, or static content too short.
• Forgetting invalidations — users keep seeing stale files after a deploy (or use versioned filenames).
• No HTTPS redirect — force HTTPS at the distribution.
• Caching personalized responses — be careful which headers/cookies are part of the cache key.

Frequently Asked Questions

Do I need CloudFront if I use S3? For a global audience, yes — it cuts latency and egress cost and lets the bucket stay private.

How do I serve a custom domain over HTTPS? Request an ACM certificate, attach it to the distribution, and create a Route 53 alias record.

How fast do changes propagate? Config changes deploy within minutes; cached objects update on TTL expiry or immediate invalidation.

Can CloudFront cache APIs? Yes for cacheable GETs; for dynamic APIs, use it mainly for TLS termination, WAF, and edge routing.

How do I improve my cache hit ratio? Cache by the minimum necessary keys (avoid including unnecessary headers, cookies, or query strings in the cache key), set generous TTLs for static assets, and serve versioned filenames so content can be cached indefinitely. A higher hit ratio means lower latency and lower origin cost.

What's the difference between an edge location and a region? Edge locations are CloudFront's many points of presence close to users for caching and delivery; AWS Regions are where your origins and most services run. CloudFront connects the two.

Summary Table

Monitoring and Logs

CloudFront reports key metrics to Amazon CloudWatch — total requests, bytes downloaded, 4xx/5xx error rates, and (most importantly) your cache hit ratio, which tells you how effectively the edge is offloading your origin. A low hit ratio usually means your cache settings or cache key are too restrictive, sending too many requests back to the origin. For request-level detail, enable standard logs (delivered to S3) or real-time logs (streamed to Kinesis) to analyze traffic, debug issues, and feed dashboards. Watching the cache hit ratio after launch and tuning TTLs and cache policies upward is one of the highest-leverage optimizations you can make, improving both performance and cost at once.

Price Classes and Regional Edge Caches

CloudFront's network has two tiers: hundreds of edge locations closest to users, backed by larger regional edge caches that hold content longer and reduce trips to your origin. You don't manage these directly, but you can control cost with price classes — choosing to serve from all locations worldwide, or restricting to cheaper regions (e.g. North America and Europe only) if your audience is concentrated there. This lets you trade a little global reach for lower data-transfer costs.

CloudFront vs Transfer Acceleration vs Global Accelerator

AWS has three edge-network services that are easy to confuse. CloudFront caches and delivers content (HTTP/HTTPS) close to users. S3 Transfer Acceleration speeds up uploads to S3 by routing them through the nearest edge. AWS Global Accelerator improves performance and failover for non-HTTP and TCP/UDP applications by routing traffic over the AWS backbone to the optimal endpoint. Rule of thumb: cache a website or API → CloudFront; faster S3 uploads → Transfer Acceleration; accelerate a TCP/UDP app or get static anycast IPs → Global Accelerator.

A Real-World Setup: Global Static Site in Five Steps

1. Build your site and upload it to a private S3 bucket.
2. Create a CloudFront distribution with the bucket as the origin and attach an Origin Access Control.
3. Request an ACM certificate for your domain and attach it; set the viewer policy to redirect HTTP to HTTPS.
4. Create a Route 53 alias record pointing your domain at the distribution.
5. Use versioned filenames for assets so deploys don't require invalidations, and add a WAF web ACL for protection.

The result is a fast, secure, HTTPS site delivered worldwide, with the origin bucket never exposed to the public internet.

Reference

This article follows the official AWS documentation. Read the full reference here: Amazon CloudFront documentation.

Conclusion

CloudFront makes your content fast, secure, and cheaper to deliver worldwide by caching at the edge. Pair it with a private S3 bucket via OAC, enforce HTTPS with a free ACM certificate, tune your cache behaviors and TTLs, add WAF and signed URLs where needed, and reach for edge compute when you need logic close to users. The payoff is a faster site, a protected and lighter-loaded origin, and lower data-transfer bills — a rare win on every axis at once.