Content & Sites

Changedetection.io

Mark

28 Sep 2025 • 3 min read

Changedetection.io is an open‑source, self‑hosted service for monitoring web pages and non‑HTML resources (HTML, JSON, PDF). It periodically snapshots content, applies selectors (CSS/XPath/JSONPath), shows diffs, and sends alerts through many channels when meaningful changes occur.

It’s aimed at developers, hobbyists, small teams and anyone who wants control over monitoring data—examples include price/restock alerts, compliance or policy change detection, API/JSON change tracking, and PDF/report surveillance. The project provides Docker and Python install paths and a web UI for everyday management.

Use Cases

Developers and hobbyists monitoring product pages, blog updates, or public APIs without relying on third‑party SaaS.
Small businesses tracking competitor price changes, inventory restocks, or contract/policy edits.
Security/compliance teams watching for unexpected website changes or leaked information in publicly accessible pages and PDFs.
Automation users who want alerts routed into Slack, Discord, webhooks or home automation systems.
Anyone who needs selective monitoring of page fragments or JSON payloads using CSS/XPath/JSONPath selectors.

Strengths

Open source and self‑hostable: full data control, no vendor lock‑in and no mandatory SaaS fees when you run it yourself.
Rich feature set: visual selectors, diff visualization (word/line/char), Playwright browser steps, PDF and JSON monitoring, and per‑watch history.
Flexible fetch strategy: a lightweight non‑JS fetcher for fast checks and an optional Playwright renderer for JS‑heavy sites and scripted interactions.
Granular per‑watch settings: configure fetcher, schedule, selectors, notifications and proxies per monitored target.
Notifications and integrations: built‑in support for Email, Slack, Discord, Telegram, Matrix, webhooks, NTFY, Office 365 and more, easing integration into existing workflows.
Docker‑first deployment: official Docker images and community Docker Compose examples make installation straightforward on VPS, NAS or container platforms.
Backup‑friendly datastore: local files/DB can be mounted in containers for standard backup and restore workflows.
Active project and community: regular releases, docs, tutorials and community threads useful for troubleshooting and examples.

Limitations

Playwright/browser fetcher is resource‑heavy and can be unstable over long runs — expect higher memory/CPU and plan for restarts or browser rotation when using many browser‑based checks.
Not turnkey at enterprise scale: the self‑hosted design suits single servers or small fleets; running thousands of high‑frequency watches requires ops work (capacity planning, sharding, proxy management).
Hosted conveniences are paid: bundled proxies and managed Playwright are part of the hosted subscription, so self‑hosting requires you to supply and manage proxies and browser infrastructure.
Sites with aggressive anti‑bot protections or frequent layout churn can cause false positives or need custom tuning (headers, proxies, selectors or scripted actions).
Documentation covers core flows well, but some advanced topics (complex Playwright flows, large‑scale proxy setups, performance tuning) rely on community guides and GitHub issues.

Final Thoughts

Changedetection.io is a practical, feature‑rich choice when you want ownership of monitoring data and control over integration and deployment. For single servers or small fleets it delivers most monitoring needs with modest operational overhead, especially when you use the lightweight fetcher and selective watchers.

Practical advice if you plan to self‑host:

Start with the Docker image and persist the datastore via a mounted volume for easy backups and upgrades.
Use the non‑JS fast fetcher for most pages; enable Playwright only for sites that require JS rendering or interaction, and limit its use to reduce resource pressure.
Plan proxies and rate limits up front for geo‑restricted or frequently checked sites; configure per‑watch proxies where necessary.
Monitor resource usage and implement lightweight restart/rotation strategies for browser runners if you run many Playwright‑based checks.
If you need large scale, SLA guarantees, or bundled proxy pools, evaluate the hosted plan or a commercial provider to avoid building extra infrastructure.