What Is Cloudflare and How Does It Speed Up and Protect Websites?
Cloudflare is a global network that sits between your visitors and your origin server, caching static files and filtering malicious traffic before it reaches you. You use it by adding your domain to Cloudflare, pointing your nameservers at Cloudflare, and letting its edge network handle DNS, TLS, caching, and DDoS mitigation. The same network also powers free public CDNs like cdnjs, which serves JavaScript, CSS, and font libraries to roughly 12.5% of all websites at a rate of about 250 billion requests per month.
The core services, and what each one actually does
Cloudflare bundles several distinct functions. They are often described together, but they solve different problems.
| Service | What it does | What changes for you |
|---|---|---|
| CDN caching | Stores copies of static assets on edge servers worldwide | Visitors download files from a nearby location instead of your origin |
| DDoS protection | Absorbs and filters volumetric attack traffic at the edge | Your origin server never sees most attack requests |
| DNS | Resolves your domain from Cloudflare's nameservers | You change nameservers at your registrar; DNS records move to Cloudflare |
| SSL/TLS | Terminates HTTPS at the edge and encrypts to your origin | Certificates are issued and renewed without manual work |
The important mental model: Cloudflare is a reverse proxy. Traffic flows through it rather than directly to your server. That single fact explains both the speed benefit (caching and proximity) and the protection benefit (filtering before requests arrive).
How the caching layer speeds up a site
When a browser requests a static file — an image, a stylesheet, a script — Cloudflare checks whether a copy already exists on an edge server near that visitor. If it does, the file is returned immediately. If not, Cloudflare fetches it from your origin, stores it, and serves it to subsequent visitors from the edge.
Two things make this fast:
- Proximity. The request travels a short distance to a nearby data center instead of crossing an ocean to your server.
- Offloaded origin. Your server handles far fewer requests, so it has capacity for the dynamic pages that genuinely need it.
Caching works best for files that rarely change. HTML pages generated per user, API responses, and anything behind a login generally should not be cached at the edge, or should be cached only briefly.
How a site uses Cloudflare through a CDN like cdnjs
You do not need to run your own Cloudflare account to benefit from the network. Public CDNs built on it let you load common libraries with a single URL.
cdnjs is described as "the free CDN for open source libraries," offering JavaScript, CSS, and font resources "globally cached on Cloudflare's network." In practice, you reference a library directly in your HTML:
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/.../style.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/.../library.min.js"></script>
The browser requests the file, Cloudflare serves it from the nearest edge location, and your own server is never involved. This is why a small site can deliver a popular library as quickly as a large one — the file is already cached close to the visitor.
Note the distinction: cdnjs is a content CDN for third-party libraries. Your own Cloudflare setup is an infrastructure CDN for your own files. They share the same underlying network but serve different purposes, and you can use both at once.
Basic setup steps
The general flow for putting your own domain behind Cloudflare:
- Create an account and add your domain. Cloudflare scans your existing DNS records and imports them.
- Review the imported records. Confirm that A, AAAA, and CNAME records point to the right origins before you switch anything.
- Change your nameservers at your registrar. Cloudflare gives you two nameserver addresses; you replace your current ones with those. This is the step that actually activates the service.
- Wait for propagation. DNS changes take time to spread, and Cloudflare shows your domain as active once it detects the new nameservers.
- Enable caching and TLS. Turn on the proxy (the orange cloud) for records you want accelerated, and choose an SSL mode that matches your origin's capabilities.
The expected result: your domain resolves through Cloudflare, static assets are cached at the edge, and HTTPS is handled at the edge.
Common problems and how to handle them
A cached file won't update. You deployed a new version of a stylesheet, but visitors still get the old one. The edge is serving its stored copy. Fixes: purge the specific file or the whole cache from the dashboard, or use versioned filenames (for example app.v2.css) so each release is a new URL that was never cached.
Something that should be dynamic is being cached. If a page shows stale or wrong content, check whether its cache rules are too broad. You can bypass the cache for specific paths or set a short time-to-live.
HTTPS errors after switching. These usually come from a mismatch between the SSL mode and what your origin actually supports. If your origin has no valid certificate, a strict mode will break the connection; a flexible mode avoids that but leaves the origin-to-edge leg unencrypted.
DNS records disappeared or changed. Records are managed at Cloudflare after the switch, not at your old registrar. Edit them in the Cloudflare dashboard.
When Cloudflare is the right fit
Cloudflare makes sense when you want caching, DDoS absorption, DNS, and TLS from one place without running edge infrastructure yourself. It is a poor fit if you need to cache highly personalized responses at the edge, or if your origin already sits behind a provider that handles these functions and adding another proxy layer creates conflicts.
For loading third-party libraries specifically, you often don't need your own account at all — a public CDN on the same network, like cdnjs, already does the caching for you.