---
title: "Change Detection — monitoring glossary"
description: "Change detection is the practice of monitoring a webpage for content modifications and alerting when something changes. It applies to text, images, prices,…"
canonical: "https://lemwatch.com/glossary/change-detection"
source: "https://lemwatch.com"
---

# Change Detection

> Change detection is the practice of monitoring a webpage for content modifications and alerting when something changes. It applies to text, images, prices, structured data, and full-page screenshots.

## Definition

 Change detection is broader than visual regression: it also covers DOM-level comparison, keyword presence/absence (e.g. ensuring 'Add to cart' appears on every product page), structured-data changes, and JSON-API response shape monitoring.

 Triggers are configurable — alert on any change, alert only on changes to a specific selector, alert only when a keyword disappears, alert when a price moves outside a range.

## Why it matters

 Change detection catches problems no other monitor sees: a CMS user accidentally publishing a draft, a third-party widget swapping in different content, a legal page being modified without legal review, a competitor changing their pricing.

 See it in the product: [Change detection](https://lemwatch.com/features).


## Related

- [Monitoring glossary](https://lemwatch.com/glossary)
- [Visual Regression](https://lemwatch.com/glossary/visual-regression)
- [Money Page](https://lemwatch.com/glossary/money-page)
- [Website Monitoring](https://lemwatch.com/glossary/monitoring)
- [All monitoring checks](https://lemwatch.com/features)
- [CLS (Cumulative Layout Shift)](https://lemwatch.com/glossary/cls)
- [CDN (Content Delivery Network)](https://lemwatch.com/glossary/cdn)