CDN (content delivery network)
Copies of your images, videos and files kept on servers around the world, close to your users, so they load quickly wherever people are.
Updated October 2026 · with examples from our own builds
What does CDN mean in practice?
A CDN sits in front of your storage. The first request for a file fetches the original; after that, nearby edge servers answer directly. For media-heavy products such as social apps and video, it is what keeps playback smooth and server load low.
Two things change when you add one. The bill shifts towards paying for delivery, and your product starts to depend on wherever its files are served from, so a script or font loaded at runtime from someone else's CDN is a dependency outside your control.
Setting one up is mostly configuration, but existing media has to be moved or re-pointed, and that step is easy to forget.
CDN at a glance
- Best for
- Images, video streams and static files
- Watch
- Delivery pricing and cache settings
- Dependency risk
- Assets loaded at runtime from someone else's CDN
Where has CDN come up in our builds?
We added a CDN URL helper with a backfill script for existing media, and designed the video pipeline to serve its HLS playlists through CloudFront. Video posting is switched off in the app today, and that pipeline has not been run end to end yet.
Replacing the forked formeo editor and renderer with our own also removed a runtime fetch of assets from the upstream project's CDN.
Common questions about CDN
Is a CDN worth it before my app has many users?
If it serves video or many images to people in different places, yes, even early. For a mostly text app, the hosting platform's built-in delivery is usually enough to start with.
What happens to old uploads when we add a CDN?
They keep their old addresses until someone re-points them. LetSlic's pipeline came with a backfill script that rewrites existing media to CDN URLs, so old and new posts are served the same way.
Related terms
Sources
Planning a product and not sure where CDN fits? Ask us, or browse all 116 terms in the glossary.