# What Is Amazon CloudFront? A Complete Guide to AWS's CDN

Key Takeaways

  • Amazon CloudFront is AWS's content delivery network (CDN), caching content at edge locations worldwide to reduce latency for end users.
  • It can serve static assets from S3, dynamic content from EC2/ALB, or any custom origin, and integrates tightly with AWS WAF and Lambda@Edge.
  • CloudFront reduces origin load and often reduces data transfer costs compared to serving everything directly from origin servers.
  • Proper cache policies and origin configuration are the difference between a CDN that actually helps and one that serves stale or uncached content.

What Is CloudFront Used For?

Amazon CloudFront is Amazon's content delivery network (CDN) — a globally distributed system of edge locations that caches your content close to end users, so requests don't have to travel all the way back to your origin server (S3 bucket, EC2 instance, load balancer, or any custom HTTP server) every time.

CloudFront is used for:

  • Serving static website assets (images, CSS, JS, video) with low latency worldwide
  • Accelerating dynamic application responses through optimized network paths, even for non-cacheable content
  • Distributing software downloads and large media files at scale
  • Adding a security layer in front of origins via AWS WAF integration, rate limiting, and geographic restrictions
  • Running lightweight compute at the edge with Lambda@Edge or CloudFront Functions

How CloudFront Works

When a user requests content through a CloudFront distribution, the request routes to the nearest edge location (AWS operates hundreds of them globally). If that edge location already has a valid cached copy, it serves the response immediately — no trip back to your origin. If not, CloudFront fetches the content from your origin, caches it according to your cache policy, and serves it to the user, with subsequent requests served from cache.

# Create a basic CloudFront distribution with an S3 origin
aws cloudfront create-distribution \
  --origin-domain-name my-static-site-bucket.s3.amazonaws.com \
  --default-root-object index.html

This single flow — edge cache hit or origin fetch-and-cache — is the core mechanic behind every CloudFront use case, whether you're serving a static site or accelerating an API.

Common Origin Types

S3 Origin (Static Content)

The most common pattern: an S3 bucket holds static assets, and CloudFront sits in front of it as the public-facing CDN layer. This also lets you keep the S3 bucket itself private, using Origin Access Control (OAC) so content is only accessible through CloudFront, not directly via the S3 URL.

{
  "DistributionConfig": {
    "Origins": {
      "Items": [
        {
          "Id": "s3-origin",
          "DomainName": "my-static-site-bucket.s3.amazonaws.com",
          "OriginAccessControlId": "E1A2B3C4D5E6F7",
          "S3OriginConfig": { "OriginAccessIdentity": "" }
        }
      ]
    },
    "DefaultCacheBehavior": {
      "TargetOriginId": "s3-origin",
      "ViewerProtocolPolicy": "redirect-to-https"
    }
  }
}

Custom Origin (Dynamic Applications)

For dynamic content — an Application Load Balancer in front of EC2 or ECS, or any HTTP(S) server — CloudFront can still add value by caching cacheable responses, compressing output, and terminating TLS at the edge closer to users, even when most responses themselves aren't cached.

aws cloudfront create-distribution \
  --origin-domain-name my-alb-1234567890.us-east-1.elb.amazonaws.com \
  --origin-protocol-policy https-only

Cache Policies and Invalidation

Getting real performance benefit from CloudFront depends heavily on correctly configured cache behaviors:

  • Cache Policy controls what's included in the cache key (query strings, headers, cookies) and the TTL for cached objects.
  • Origin Request Policy controls what gets forwarded to the origin on a cache miss.
  • Invalidations let you manually expire cached objects when content changes before the TTL naturally expires — useful for deployments, but costly at scale, so most teams prefer versioned object keys (e.g., app.v2.js) over frequent invalidations.
# Invalidate cached paths after a deployment
aws cloudfront create-invalidation \
  --distribution-id E1EXAMPLE2DISTRO \
  --paths "/index.html" "/assets/*"

Security: WAF, Geo-Restriction, and Signed URLs

CloudFront integrates directly with AWS WAF, letting you block malicious traffic (SQL injection attempts, bad bots, rate-limit abuse) at the edge before it ever reaches your origin. You can also apply geographic restrictions to block or allow specific countries, and use signed URLs or signed cookies to control access to private content like paid video or licensed downloads.

aws cloudfront get-distribution-config --id E1EXAMPLE2DISTRO | \
  jq '.DistributionConfig.WebACLId'

Diagram: CloudFront Request Flow

<svg viewBox="0 0 700 280" xmlns="http://www.w3.org/2000/svg" role="img" aria-label="CloudFront edge caching request flow diagram">
  <style>
    text { font-family: -apple-system, Segoe UI, Roboto, sans-serif; font-size: 13px; fill: currentColor; }
    .box { fill: none; stroke: currentColor; stroke-width: 1.5; rx: 8; }
    .label { font-size: 11px; opacity: 0.75; }
    .arrow { stroke: currentColor; stroke-width: 1.5; fill: none; marker-end: url(#arrowhead); }
    .dashed { stroke-dasharray: 4 3; }
  </style>
  <defs>
    <marker id="arrowhead" markerWidth="10" markerHeight="10" refX="8" refY="3" orient="auto">
      <path d="M0,0 L8,3 L0,6 Z" fill="currentColor" />
    </marker>
  </defs>

  <rect x="20" y="110" width="120" height="60" class="box" />
  <text x="35" y="140" font-weight="600">User</text>
  <text x="35" y="158" class="label">Request</text>

  <path class="arrow" d="M140,140 L210,140" />

  <rect x="220" y="90" width="160" height="100" class="box" />
  <text x="235" y="115" font-weight="600">CloudFront Edge</text>
  <text x="240" y="135" class="label">Cache hit? Serve now</text>
  <text x="240" y="153" class="label">Cache miss? Fetch origin</text>

  <path class="arrow dashed" d="M380,120 L540,70" />
  <text x="390" y="90" class="label">Miss path</text>

  <path class="arrow" d="M300,190 L300,230" />
  <text x="230" y="250" class="label">Cached response served to user</text>

  <rect x="470" y="30" width="170" height="60" class="box" />
  <text x="485" y="55" font-weight="600">Origin</text>
  <text x="485" y="73" class="label">S3 / ALB / custom</text>
</svg>

FAQ

What is CloudFront in AWS? CloudFront is Amazon's CDN — a globally distributed network of edge locations that caches your content close to end users to reduce latency and offload traffic from your origin servers.

What is CloudFront used for besides static websites? Beyond static assets, it's used to accelerate dynamic application traffic, distribute large downloads, add a WAF-backed security layer, and run edge compute via Lambda@Edge or CloudFront Functions.

Do I need an S3 bucket to use CloudFront? No — CloudFront supports any HTTP(S) origin, including Application Load Balancers, EC2 instances, or external servers, not just S3.

How do I update content without waiting for cache expiry? Use CloudFront invalidations for occasional updates, but for frequent deployments, versioned object paths (e.g., appending a build hash to filenames) avoid invalidation costs and guarantee fresh content immediately.

Need Help Architecting Your CDN Setup?

F9infotech's AWS team designs CloudFront distributions tuned for real-world cache hit ratios, security, and cost — not just default settings. Talk to us about optimizing your content delivery architecture.