SignalWatch
Website change monitoring
Know when a public page changes, and get the diff.
Website change monitoring is a schedule plus a comparison. SignalWatch fetches a public URL, fingerprints the visible text, and when that text moves — or the fetch fails and later recovers — it sends a unified diff by email, Slack, Discord, or a signed JSON webhook.
No card. 3 monitors on the free plan. See a live one on Hacker News.
How a check works
- You add a public URL. Optional: a CSS selector, an ignore regex, ignore-order for lists that reshuffle, and a minimum change ratio.
- The first successful fetch is the baseline. Nothing is alerted yet.
- Later fetches compare visible text. A real edit sends
content.changedwith the diff. A failed fetch sendscheck.down, and recovery sendscheck.up.
Alerts retry for hours if Slack or your webhook is down. Use Send test alert before you wait on a real change. Curl, Python, n8n and GitHub Actions examples are on the examples page.
Pages this is for
- Competitor pricing and packaging pages
- Vendor status banners and incident notes
- Changelogs, release notes, and docs you depend on
- Terms, fee schedules, and policy pages
What it will not do
- Render JavaScript, log in, or solve a CAPTCHA
- Take screenshots or pixel-diff a layout
- Replace a ping-only uptime product if all you need is “is port 443 open”
If you need a visual inbox, start from the comparison with Visualping, Distill, Hexowatch, Wachete, and Fluxguard. If you need the diff in a workflow, stay here.
FAQ
What is website change monitoring?
A scheduled fetch plus a comparison. SignalWatch stores the visible text and, when it changes, sends the unified diff so you can see the old line and the new line.
How do I get an alert when a webpage changes?
Paste the URL above and add an email. On the free plan the check runs every 15 minutes. Slack, Discord, and signed JSON webhooks are included on that same plan.
Will it see content that loads with JavaScript?
No. It reads the HTTP response. The signup preview flags a JavaScript shell before you create the monitor.
How much does it cost?
Free for 3 monitors. Pro is $12/month or $79/year for 50 monitors at 5 minutes. Business is $29/month or $199/year for 500 monitors at 2 minutes.