On-Demand Revalidation Is ISR With a Trigger Instead of a Clock

Instead of waiting for a fixed interval to elapse before regenerating a page, on-demand revalidation lets a content update trigger the regeneration immediately — a CMS publish webhook calls an endpoint, and the specific page that changed gets rebuilt, rather than every page waiting out the same generic window.

The trade is real: this requires wiring something up on the content-source side that a purely time-based approach doesn't — a webhook, an API call, something that actually knows when content changed and can say so.

For content that changes on an unpredictable schedule — breaking news, inventory, anything where 'stale for up to five minutes' is a real problem rather than a rounding error — this is usually worth the extra wiring. For content that changes on a predictable cadence, the fixed interval was already doing the job.