Re:Show HN: I built a tool that watches webpages and exposes...
by vkuprin on Thursday March 12, 2026 @07:21AM
(#47349141)
Fair point, and I should have been upfront about this earlier. The backend is a fork of changedetection.io. I've built on top of it — added the browser extension workflow, element picker, billing, auth, notifications, and other things — but the core detection engine comes from their project. That should have been clearly attributed from the start, and I'll add it to the docs and about page.
changedetection.io is a genuinely great project. What I'm trying to build on top of it is the browser-first UX layer and hosted product that makes it easier for non-technical users to get value from it without self-hosting and AI focus approach
P.S -> I've also added an acknowledgements page to the docs: https://docs.sitespy.app/docs/acknowledgements
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Re:Show HN: I built a tool that watches webpages and exposes...
by vkuprin on Thursday March 12, 2026 @02:05PM
(#47354861)
Yes — the project is Apache 2.0 licensed (https://github.com/dgtlmoon/changedetection.io/tree/master?t...), which permits forking and commercial use. There's also a COMMERCIAL_LICENCE.md in the repo for hosting/resale cases, and I've reached out to the maintainer directly about it. Attribution is here: https://docs.sitespy.app/docs/acknowledgements
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Summary: What Is Objectively Provable
- The extension stores its config under the key changedetection_config
- 16 API endpoints in the extension are 1:1 matches with changedetection.io's documented API
- 16 data model field names are exact matches with changedetection.io's Watch model (including obscure ones like time_between_check_use_default, history_n, notification_muted, fetch_backend)
- The authentication mechanism (x-api-key header) is identical
- The default port (5000) matches changedetection.io's default
- Custom endpoints (/auth/, /feature-flags, /email/, /generate_key, /pregate) do NOT exist in changedetection.io — these are proprietary additions
- The watch limit error format is completely different from changedetection.io's, adding billing-specific fields (current_plan, upgrade_required)
- The extension ships with error tracking that sends telemetry (including user emails on login) to the developer's GlitchTip server at 100% sample rate
The extension is provably a client for a modified/extended changedetection.io backend. The open question is only the degree of modification - whether it's a fork, a proxy wrapper, or a plugin system. But the underlying engine is unambiguously changedetection.io.