First: what is a CDN?
A CDN (Content Delivery Network) is a service that keeps copies of your website's files and delivers them to visitors quickly, usually from servers spread across many locations. It takes load off your main hosting and makes pages load faster.
A regular CDN delivers files exactly as they are. Upload a 4 MB photo and a regular CDN will deliver that 4 MB photo quickly, but it's still 4 MB.
So what's different about an image CDN?
An image CDN does one extra thing that matters a lot: it changes the image before delivering it. From one original file it can create versions with different sizes, formats and quality, to suit each page and each browser.
The request is usually written right into the image link. An example with Simpanan:
https://cdn.simpananawan.com/tr:w-600,f-auto/u/you/photo.jpgThis link means: take photo.jpg, make it 600 pixels wide, and send it in the best format the visitor's browser supports.
How an image CDN works
- Storage. You upload the original image once, at the best quality you have.
- Request. Your web page asks for the image through a link that includes size and format options.
- Transformation. On the first request, the CDN creates a new version from the original using those options.
- Cache. The result is stored, so later requests for the same version are delivered without processing again.
- Delivery. The visitor receives a file far smaller than the original.
What an image CDN gives you
- Faster pages. Smaller images make pages appear sooner, which shows up in Core Web Vitals such as LCP. Details are in our guide how to compress images for a website.
- Modern formats without effort. AVIF and WebP go automatically to browsers that support them, with no separate files to prepare. See WebP vs AVIF.
- One original for every size. Thumbnails, banners and responsive images all come from one file. Changing the design? Change a number in the link.
- Lighter hosting. Images come from the CDN, not your web host, saving your hosting's storage and bandwidth.
- Time saved. No more exporting five versions of every image by hand.
When do you need an image CDN?
An image CDN makes the biggest difference when:
- Your website has lots of images, like an online store, portfolio, news site or catalogue.
- Images are uploaded by many people who don't always shrink them first.
- You need different sizes for phones, tablets and desktops.
- Your hosting is limited in space or bandwidth.
On the other hand, for a small website with a handful of well-optimized images, compressing them by hand may be all you need.
How to choose an image CDN
Questions worth asking before you choose a service:
| Question | Why it matters |
|---|---|
| Can size and crop be set in the link? | This is the core of an image CDN. Without it, you still make versions by hand. |
| Is the format chosen per browser automatically? | So visitors get AVIF or WebP without broken images on older browsers. |
| What about animated GIFs and transparency? | Some services lose animation or transparent backgrounds when converting. |
| Is there a media library? | Uploading, organizing folders and searching is far easier than uploading through code. |
| Which other file types are supported? | Video, PDFs and fonts are often needed in the same place. |
| What are the limits, and what does it cost? | Check file size, storage and bandwidth limits, and what happens when you go over. |
An example: Simpanan
Simpanan is an image CDN and media library. You upload files or whole folders through the library, then use their links with options such as w-, h-, q- and f-auto. Animated GIFs keep playing, transparency is kept, and videos, PDFs and fonts can live in the same place. Everything is on the features page.
Common questions
Is an image CDN the same as image hosting?
Not quite. Image hosting only stores and delivers files as they are. An image CDN also changes an image's size, format and quality before delivering it, based on the request in the link.
Does an image CDN help SEO?
Indirectly, yes. Google uses page speed, including Core Web Vitals such as LCP, as one of its page experience signals. Lighter images help pages appear sooner.
Are my original images changed?
No. The original file stays intact. Each smaller version is made separately from it.