CDN

A CDN (content delivery network) is a globally distributed set of servers that cache copies of your files close to users. When someone requests an asset, the nearest edge location serves it instead of your origin, cutting latency and offloading traffic. CDNs speed up images, video, downloads, and static sites worldwide.

The core idea is proximity. Without a CDN, a user in Sydney requesting a file from a server in Virginia waits for a round trip across the planet on every request. A CDN keeps cached copies at hundreds of edge locations, so that user is served from a nearby node — often in single-digit milliseconds.

Beyond speed, a CDN protects your origin. Because the edge absorbs the vast majority of requests, your storage backend only sees the occasional cache miss. That shields you from traffic spikes and reduces the egress you pay on the origin side.

What a CDN serves well are static, cacheable assets: images, video, fonts, JS/CSS bundles, downloads, and any file that doesn't change per-request. Cache behavior is driven by headers like Cache-Control and validated with ETag.

Related terms

Content delivery network

A content delivery network works by caching your files at edge locations worldwide and routing each user to the nearest one, usually via anycast DNS. The edge serves cached copies directly; on a cache miss it fetches from your origin once, stores the result, then serves every later request locally.

Egress

Egress is the data that leaves a cloud provider's network — typically the bytes served to users when they download files or load assets. Most object-storage providers bill egress per gigabyte, so a popular file or a busy CDN can make bandwidth, not storage, the dominant line on your bill.

Cache-Control

Cache-Control is an HTTP header that tells browsers and CDNs how to cache a response — for how long, and whether they may store it at all. Directives like max-age, public, private, no-cache, and immutable set freshness, control revalidation, and decide how aggressively an asset is reused.

ETag

An ETag (entity tag) is an identifier a server assigns to a specific version of a resource, often a hash of its contents. Clients send it back via the If-None-Match header so the server can reply 304 Not Modified when nothing has changed, saving bandwidth. It also helps detect mid-update conflicts.

How files.link fits in

Every public file you upload to files.link is delivered over a global CDN automatically — there's no separate CDN to wire up or configure. image CDN.

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