Definition
Bandwidth in web hosting is the volume of data transferred between your site and its visitors over a given period, usually measured per month. Every page view consumes bandwidth equal to the size of the HTML, images, CSS, JavaScript and other assets the visitor loads, so a media-heavy page can use many times the data of a plain text one. Most hosting plans either include a generous monthly allowance, throttling or charging once you exceed it, or, on cloud and platform hosts, bill it per gigabyte, often a few cents per GB after a free tier. Measurement happens at the server's network interface, so bot crawls and attack traffic count too. Bandwidth is one of the biggest cost drivers at scale, which is why CDNs and platforms like Cloudflare Pages (no bandwidth charges) become significantly cheaper than per-GB platforms once traffic grows, since the CDN absorbs most requests at the edge rather than the origin server.
How it works
A 100 KB page viewed 10,000 times in a month uses roughly 1 GB of bandwidth. Add images, video and a typical front-end stack and per-visit numbers grow fast. Hosts measure bandwidth at the server's network interface, so anything served (including bots and DDoS traffic) counts.
Why it matters
For low-traffic sites, the bandwidth allowance is rarely a constraint. For high-traffic sites, especially those serving images or video, bandwidth cost can dominate the bill. A CDN absorbs most requests at the edge, dramatically cutting origin bandwidth and often paying for itself.