Security

How to Use a CDN to Speed Up and Protect Your Website

Discover how UnderHost’s powerful CDN solution—UnderEDGE—dramatically improves your website’s load times, global performance, and protection from DDoS attacks. Learn what a CDN is, how it works, and how you can enable it on your hosting account today.

Short answer: A CDN (content delivery network) stores copies of your site’s files on servers around the world and serves each visitor from a nearby location. It speeds up pages for distant visitors, takes load off your hosting, and adds a layer of protection. To use one, point your domain or a CDN hostname at the CDN, set caching rules that skip logged-in and checkout pages, and test before and after.

How a CDN works

Without a CDN, every visitor downloads every file from your server, wherever they are. With a CDN, the first visitor in a region causes the CDN to fetch a file from your server (the origin) and keep it. Later visitors in that region get it from the nearby CDN location, which is faster and saves your server the work.

What a CDN helps with

Benefit When it matters most
Faster loading for distant visitors Your audience is spread across countries or continents
Less load and bandwidth on your hosting Image-heavy sites, downloads, traffic spikes
Protection Absorbing floods and filtering bad bots before they reach the server
Free or included HTTPS at the edge Simplifies certificates for static hostnames

A CDN does not fix a slow server response for pages that cannot be cached, such as carts and dashboards. Page caching and a fast server still matter. See our site speed guide.

Two ways to set up a CDN

Method How it works Good for
Full-site proxy Your domain’s DNS points to the CDN, which forwards requests to your server Speed and protection for the whole site
Static hostname (pull zone) Images, CSS and JavaScript load from a CDN hostname such as cdn.example.com Offloading heavy files with minimal DNS changes

Step-by-step setup

  1. Measure the current speed of key pages with PageSpeed Insights, so you can compare later.
  2. Choose the setup method and create the CDN zone, with your server as the origin.
  3. Update DNS: either change nameservers or add the CNAME the CDN gives you.
  4. For a static hostname, tell your CMS to use it, for example with a CDN plugin for WordPress.
  5. Set caching rules (below), and turn on HTTPS for the CDN hostname.
  6. Test pages logged in and logged out, and on a phone, then measure again.

Caching rules that work

  • Cache for a long time: images, fonts, CSS and JavaScript with versioned file names.
  • Cache briefly or not at all: HTML pages that change often.
  • Never cache: admin areas, login pages, carts, checkout and account pages, and any request with a login or cart cookie.
  • Purge after changes: clear the CDN cache when you update a design or replace files with the same name.

Security features to turn on

  • ✓ HTTPS between visitors and the CDN, and between the CDN and your server.
  • ✓ Hotlink protection, so other sites cannot embed your images at your cost.
  • ✓ Bot and rate-limit rules for login and search pages.
  • ✓ Make sure the origin firewall allows the CDN’s IP ranges and still sees real visitor IPs.

For a common setup on cPanel, see our Cloudflare and cPanel guide.

Which sites benefit most

Site Why
Online stores Product images load faster; protection for checkout and login pages
Media and portfolio sites Large images and downloads served close to visitors
Sites with an international audience Distance is the main cause of slow loading for far-away visitors
Small local sites Less benefit if visitors are near the server, but protection can still help

Troubleshooting

Problem Likely cause Fix
Old files still showing The CDN cache has the old version Purge the file or the whole cache.
Logged-in users see others’ content Personal pages were cached Exclude account, cart and admin pages, then purge.
Mixed content warnings Some files still load over HTTP Use HTTPS URLs everywhere, and enable HTTPS on the CDN hostname.
Visitors blocked by the server The firewall blocks CDN IP addresses Allow the CDN’s ranges and restore real visitor IPs.

UnderEDGE CDN

UnderHost offers its own CDN, UnderEDGE, which works with shared hosting, VPS and dedicated servers. See the product page in @CustomerPanel for current locations, limits and prices, or ask our team which setup suits your site.

Need help with this?

Want faster pages worldwide? Ask our team about UnderEDGE CDN for your site.

Contact @CustomerPanel

Frequently asked questions

Does a CDN work with shared hosting?

Yes. A CDN sits in front of any hosting type, including shared hosting.

Will a CDN improve my SEO?

Indirectly. Faster pages improve Core Web Vitals and the visitor experience, which search engines take into account.

Which pages should a CDN not cache?

Admin, login, cart, checkout and account pages, and any request from a logged-in user.

Do I need to change nameservers to use a CDN?

Only for a full-site proxy. A static hostname needs just a CNAME record.

How do I clear the CDN cache?

Use the purge option in the CDN dashboard, for one file or the whole site.