What Is a CDN Cache? How It Works and Differences Explained

If you’ve ever hit refresh and wondered why a site loads instantly the second time, you’re looking at caching in action. But not all caches work the same way — browser cache sits on your device, while a CDN cache spreads across servers worldwide. That difference matters more than it sounds when you’re trying to speed up a site or troubleshoot loading issues.

Primary Function: Stores copies of website content on global servers · Key Benefit: Reduces latency by serving from nearby edge servers · Core Difference from Browser Cache: Shared across users vs local per-device storage · Common Provider Example: Cloudflare, Akamai

A CDN caches content across distributed edge servers globally, dramatically reducing latency for geographically distant users.

What is the difference between browser cache and CDN cache?

Browser cache stores static resources like images, CSS, and JavaScript locally on the user’s device for faster repeat visits. CDN cache stores content copies on distributed edge servers worldwide to deliver from locations closest to users. Browser cache is device-specific and user-controlled via settings, while CDN cache is shared across users and provider-managed.

Browser cache basics

• Sits on the user’s device (local storage)
• Controlled by the user via browser settings
• Serves only that specific user on that specific device
• Typical optimal TTL: 5-10 minutes

CDN cache scope

• Distributed across provider’s global server network
• Provider manages via dashboard or API
• Shared across all users in that region
• Typical configurable TTL: 1 hour or longer with purging

Are CDNs just caches?

A CDN performs caching as its core function, but modern CDNs do much more than store copies of files. According to Fastly (CDN provider specializing in edge delivery), caching is a core functionality of a CDN, but load balancing, DDoS protection, and intelligent routing are equally important. Cloudflare (major CDN provider) offers these additional services alongside their caching infrastructure.

Beyond caching in CDNs

• Load balancing across multiple origin servers
• DDoS protection and security features
• Intelligent traffic routing
• Machine learning for dynamic content caching (Imperva uses this approach)

Additional CDN features

• Automatic failover if origin servers go down
• Real-time analytics and monitoring
• API-based management and automation
• SSL/TLS termination

What is a Content Delivery Network (CDN)?

A Content Delivery Network (CDN) is a geographically distributed network of proxy servers that cache content closer to end users. According to Cloudflare (CDN provider offering official caching documentation), CDNs improve the end user’s website experience by reducing latency and handling traffic spikes. The network consists of edge servers placed in data centers worldwide.

Core components

• Origin server (your primary web server)
• Edge servers (distributed globally)
• DNS routing (directs users to nearest edge)
• Cache storage (stores content copies)

How it integrates caching

• Cache-Control headers determine what gets cached
• s-maxage controls CDN TTL separately from browser TTL
• Automatic purging when content updates
• Version-based cache busters enable long TTLs

How do CDNs work?

When a request arrives at a CDN, it first checks the edge cache at the nearest server. If the content is cached (cache hit), it serves immediately. If not (cache miss), the CDN fetches from the origin server, stores a copy at the edge, and then delivers to the user. This workflow, documented by Technori (technical publisher with detailed caching workflows), dramatically reduces latency — a German user accessing a US origin sees response times drop from 200-300ms to under 20ms when served from Frankfurt edge servers.

Content request flow

• User’s browser requests a file (e.g., image.css)
• DNS routes request to nearest CDN edge server
• CDN checks if file is cached at that edge
• If cached: serves immediately to user
• If not cached: fetches from origin, caches, then serves

Cache hit vs miss

• Cache hit: content served from edge, fastest response
• Cache miss: CDN fetches from origin, adds ~100-200ms
• First visit typically a cache miss
• Subsequent visits served from edge cache

How do I clear my CDN cache?

CDNs offer multiple ways to purge cached content. According to Fastly (CDN provider specializing in edge delivery), providers can purge cache assets when updates occur, unlike browser cache which users control. Use your provider’s dashboard, API, or CLI tools to clear specific files or the entire cache instantly.

Purge methods by provider

• Cloudflare: Purge via dashboard or API call
• Fastly: Purge via API or Fastly CLI
• Imperva: Proxy cache management through dashboard
• Akamai: Control Center or API-based purging

When to clear

• After deploying website updates
• When seeing stale content in production
• After fixing cached errors or bugs
• Before major traffic events (sales, launches)

Browser Cache vs CDN Cache: A Practical Comparison

Two caching layers serve most requests before they ever hit your origin server: browser cache handles repeat visits on the same device, while CDN cache serves content to users across regions from shared edge servers. According to Technori (technical publisher with detailed caching workflows), an optimized system typically sees 60–80% of requests served by browser cache, 15–30% by CDN, and less than 1% reaching the database.

Browser caching and CDN caching serve different purposes at different scales, with browser cache handling local repeat visits and CDN cache serving global audiences from edge servers.

The key distinction is control and scope: browser cache is yours to manage on your device, while CDN cache operates across a distributed network with provider-side controls. For static assets, combining a short browser TTL with a longer CDN TTL and purge-on-update gives you the best of both worlds.

How to Configure CDN Caching: A Step-by-Step Guide

Setting up CDN caching properly requires configuring HTTP headers that control how long both browsers and edge servers cache your content. The Fastly documentation (CDN provider specializing in edge delivery) recommends using Cache-Control headers with separate directives for browser and CDN TTLs.

1. Set origin server Cache-Control headers: Configure your web server to send appropriate Cache-Control directives with your content.
2. Define browser TTL (max-age): Set max-age to 5-10 minutes for typical web content. Example: Cache-Control: public, max-age=300
3. Define CDN TTL (s-maxage): Set s-maxage separately to control how long CDNs cache. Example: s-maxage=3600 gives CDN 1-hour cache.
4. Use version-based cache busters: Include version strings in filenames (e.g., /style.v2.css) to enable long TTLs with automatic cache busting on updates.
5. Set up automatic purging: Integrate your CDN’s purge API into your deployment pipeline to clear cached content whenever you push updates.
6. Test and monitor: Use browser DevTools to check cache headers, and monitor CDN analytics for hit rates and cache efficiency.

Most requests never reach the bottom of the stack: 60–80% served by browser cache, 15–30% by CDN.

— Marcus, Author (Technori)

CDNs are much more efficient, since their cache is shared between all your users.

— Fastly Team, CDN Provider (Fastly)

Studies show that delivering content from a geographically closer server can reduce Time to First Byte by up to 50 percent.

— AccuWeb Team, Cloud Provider (AccuWeb.Cloud)

Related reading: Microsoft Authenticator App Guide · Gmail Log In Guide

While browser cache stays local, the CDN cache workings guidehighlights how edge servers worldwide slash latency for faster site loads.

Frequently asked questions