Website Change Detection

Overview

Change Detection watches a website for you. Enter a URL and Notifier scans the site, following links on the same domain up to the number of pages you choose. After that it checks those pages on a schedule and alerts you when their text changes, when a new page appears, or when a page disappears.

People use it to follow competitors' pricing and feature pages, catch unexpected edits to their own site, watch terms of service and policy pages, and track job boards, docs and changelogs.

Watching a Site

1. Go to Change Detection in the sidebar of your monitoring dashboard.
2. Click Watch a site and enter the URL to start from.
3. Choose how many pages to watch. Set it to 1 to watch only that page.
4. Choose how often to check, and where alerts should go.
5. Save. The first scan starts within a minute and takes about a second per page.

The first scan records what each page says. You won't get alerts from it; alerts start once something changes after that.

Plan Limits

Pages are shared across all your watched sites. For example, on Free you could watch one site with 25 pages, or three sites with 10, 10 and 5 pages.

What Counts as a Change

Notifier compares the visible text of each page. Changes to markup, styles, scripts and tracking code are ignored. You get an alert when:

• Text on a page is added, edited or removed. The alert shows a short excerpt of the new text.
• A new page appears on the site (linked from a page you watch), while you have pages left in the watch.
• A page disappears (returns 404 or 410).
• A page starts blocking our checker.

One check sends one alert per channel that lists every page that changed, so a site redesign doesn't flood you.

Fewer false alarms

Many sites show slightly different content on every visit: rotating testimonials, "latest posts" widgets, A/B tests. Notifier filters these out:

• When a page looks different, it's fetched a second time, and only changes seen both times count.
• Sections that come and go between visits are learned and ignored from then on.
• The first two checks after a page is added only learn the page.
• Text that only disappears is confirmed at the next check before you're alerted.
• Relative times ("3 minutes ago"), clock times and random tokens are ignored.

Alerts

Change alerts can go to email, Slack, Discord, Microsoft Teams, Telegram and webhooks, using the same integrations as your monitors. Telegram, Teams and webhooks need the Solo plan or above. SMS and phone calls aren't used for content changes.

Webhooks receive a page.changed event. Subscribe to it when you create or edit a webhook. See Webhooks for signing and retries.

{
  "event": "page.changed",
  "occurred_at": "2026-10-23T18:00:00Z",
  "watch": {"id": 42, "name": "Competitor", "url": "https://example.com/", "dashboard_url": "https://notifier.so/new/monitoring/change-detection/watch?id=42"},
  "changes": [
    {"url": "https://example.com/pricing", "kind": "changed", "sections_added": 2, "sections_removed": 1, "snippets": ["Pro plan now $29 per month"]},
    {"url": "https://example.com/new-feature", "kind": "added", "sections_added": 0, "sections_removed": 0, "snippets": ["New feature"]}
  ]
}

kind is one of changed, added, removed or blocked.

Blocked Pages

Some sites use bot protection (Cloudflare challenges, DataDome, PerimeterX, Akamai, CAPTCHAs) that stops automated checks, and some only show their content after JavaScript runs. Notifier detects both and marks those pages as Blocked instead of reporting false changes.

Reading these pages needs premium fetching (residential IP addresses and a real browser), which is coming to paid plans.

What We Store

Notifier doesn't keep copies of the pages it checks. For each page it stores a fingerprint (hash) of the text, a fingerprint per paragraph, the page title, and up to three short excerpts of new text per change so alerts can show what changed. Change history is kept for 180 days.

For Site Owners: Our Crawler

Change Detection checks pages with the user agent NotifierChangeDetection/1.0. It fetches one page at a time with a pause between requests, only follows links on the same site, and follows your robots.txt when discovering pages. To stop it from crawling your site, add this to your robots.txt:

User-agent: NotifierChangeDetection
Disallow: /

The exact page a user entered is still checked, the same way a person would visit it. Questions? Email support@notifier.so.