What is change monitoring?
A monitor is a URL, a cadence and a definition of the value to watch — either a CSS selector’s text or an extracted set of fields. Each scheduled check normalizes the value, hashes it, and compares it to the last hash. Unchanged checks do nothing but appear in the history; a change posts a signed webhook carrying both hashes and an excerpt.
Why it matters
Polling a page yourself means storing previous state, handling flaky renders, and writing the diff. Hash-comparison on a schedule with a push on change moves all three server-side — at the cost of paying for every check, changed or not.