Detecting changes in HTML page sources

For some webpages, relevant information is best accessed by checking the HTML page source.

Use Case

For example, the HTML response of web shops like https://www.campuspoint.de contains the product listings in JSON format which is then processed client-side with JS to produce the final markup. One could use the JS-enabled Playwright-content-fetcher for such a webpage, but checking against the page source is more efficient.

Approach

• In the General tab, prepend the target URL with source: (example: source:https://www.campuspoint.de/mobile/notebooks/lenovo/thinkpad-t-serie/thinkpad-t14s.html)
• In the Request tab, choose the "Basic fast Plaintext/HTTP Client" fetch method
• Choose a suitable trigger in the Filters & Triggers tab, for example the regex-based "Extract text" one.
  • Example: use /"product_count":(\d+)/i to check when campuspoint.de adds new models of a certain laptop series to their inventory.

more at https://changedetection.io/tutorial/source-code-monitor-how-get-alerts-changes-html-source-code