🔔 Website Change Monitor — Page Diff & Content Alerts

Monitor any number of web pages for changes automatically. Get detailed diff reports showing exactly what was added, removed, or modified since your last check. Run it on a daily or weekly schedule and receive actionable change alerts without manually refreshing pages. This is the text-content counterpart to visual screenshot monitoring — faster, cheaper, and easier to parse programmatically.

🎯 Why Website Change Monitor?

Manually checking competitor pricing pages, regulation updates, job postings, or product stock status is a waste of time. This actor automates the entire detection pipeline:

1. Run 1 (Baseline): Fetches each URL, extracts the monitored content, computes a SHA-256 hash, and stores the full text snapshot in key-value storage. Returns "baseline saved" for every URL.

2. Run 2+ (Diff): Re-fetches each URL, compares the hash against the stored baseline. If different → computes a line-by-line diff, reports what changed (added/removed lines + % change), and updates the baseline so the next run compares against the latest version.

3. Schedule it: Set up a daily or weekly recurring run in Apify Console. Each run produces a structured dataset you can pipe to email, Slack, or any webhook via Apify Integrations.

🆚 Screenshot Monitoring vs. Change Monitoring

Feature	Screenshot Capture	Change Monitor
Detection method	Visual (pixel comparison)	Text (content diff)
File size	~1–5 MB per URL	~1–5 KB per URL
Cost per check	Higher (rendering overhead)	Lower (HTTP fetch only)
Best for	Visual regression, design QA	Text content, pricing, availability
Machine-readable diff	❌	✅ (added/removed lines, %)
Parse with scripts	Hard (requires CV)	Easy (JSON diff report)

Use both together — screenshots for visual changes, change monitor for content changes.

📊 Output Fields

Field	Description
url	The monitored URL
hasChanged	true if content differs from previous run
changePercent	Approximate percentage of lines changed (0–100)
addedLines	Number of new lines detected
removedLines	Number of lines no longer present
currentContentHash	SHA-256 hash of current content
previousContentHash	SHA-256 hash of previous baseline
diffSummary	Human-readable summary of added/removed lines (first 5 each)
checkedAt	ISO 8601 timestamp

⚙️ Smart Filtering

Monitor Specific Page Sections

Use cssSelectors to focus on what matters. Instead of monitoring the entire page (which includes ads, nav bars, footers), target exactly the content you care about:

["h1", ".price-value", "#job-listings", "[data-testid='stock-status']"]

Ignore Noisy Elements

Use ignoreSelectors to strip out dynamic elements that change on every page load but aren't meaningful — timestamps, ad containers, session IDs, random recommendation widgets:

[".timestamp", "#dynamic-ad", ".recommendations-carousel", ".live-counter"]

Strip Numbers

Enable stripNumbers: true to ignore changes that only involve numbers. Perfect for pages where the meaningful content stays the same but counters, view counts, or timestamps fluctuate:

Before: "Viewed 1,234 times | Updated 2026-06-30"
After:  "Viewed #,### times | Updated ####-##-##"

🎯 Real-World Use Cases

Competitor Price Tracking

Monitor /pricing pages of 50 competitors. Get alerted when any of them changes their pricing tiers, feature lists, or plan names. Combine with a daily Apify schedule and a Slack webhook integration.

Regulation & Legal Compliance

EU Digital Services Act, SEC filings, FDA recalls — government and regulatory pages publish updates without RSS feeds. Monitor them and get diffs of exactly what changed in the regulation text.

Job Board Monitoring

Track company career pages for new job postings. Monitor specific CSS selectors that contain job listings. When a new role appears → diff shows the new job title and description.

E-Commerce Stock & Price Alerts

Monitor product pages for "Out of Stock" → "In Stock" transitions. Target the stock status element and get alerted when availability changes.

News & Blog Monitoring

Track competitors' blog pages or news sections. See when new articles are published and what their headlines are — without visiting each site manually.

🚀 Setup for Recurring Monitoring

1. First run: Execute once with all your target URLs → establishes baselines
2. Schedule: In Apify Console, set up a recurring schedule (daily at 9 AM, hourly, etc.)
3. Integrate: Connect the dataset to Make/Zapier/n8n → send email/Slack alerts when hasChanged: true
4. Review: Check the diff summary to decide if the change is worth acting on

💰 Pricing

Pay per event — you're charged only for the HTTP requests made during each monitoring run. No monthly subscription, no minimum usage. Each URL check costs a fraction of a compute unit. Monitoring 100 URLs daily costs approximately $2–5/month on Apify's free tier and scales linearly.

❓ FAQ

Q: How is "change" detected? A: The actor computes a SHA-256 hash of the extracted text content. If the hash differs from the stored baseline → change detected. It then does a line-by-line comparison to produce the diff summary.

Q: Where are baselines stored? A: In Apify's key-value store under the actor's namespace. They persist across runs and are automatically updated after each detected change.

Q: Can I reset baselines? A: Yes — delete the key-value store records via Apify Console's Storage tab, or just run once with different input fields to create fresh baselines.

Q: Does it handle JavaScript-rendered pages? A: This actor uses HTTP fetch (got-scraping), which handles server-rendered content. For JavaScript-heavy SPAs, use the Screenshot Capture actor or a custom Playwright-based monitor.

Keywords: website change monitor, page change detection, website diff tool, content change alert, web page monitoring, competitor price tracker, regulation change monitor, automated website monitoring, page content tracker, url change detection, website change alert api, content monitoring tool, page diff api, website change detection service, recurring website checker

How do I get alerted when a competitor changes their pricing page?

Add the pricing page URLs and target the price section with cssSelectors. On each scheduled run the monitor diffs the text and flags exactly what changed so you can alert via Slack or email.

How do I monitor a page while ignoring ads and timestamps?

Use ignoreSelectors to strip ad, nav and timestamp elements before comparison, or enable stripNumbers to skip numeric-only changes, so you only get alerts on meaningful content edits.

📝 Changelog

2026-07-01

• Maintenance pass: re-verified end-to-end on live data and confirmed successful runs within the 5-minute quality window on the default input.
• Sharpened Store metadata (SEO title & description) and expanded the FAQ with high-intent, long-tail questions for easier discovery in Google and Apify Store search.
• Added ready-to-run example tasks that cover common real-world use cases.