I lost a deal last month.

Prospect told me my competitor had dropped
their pricing two weeks earlier. Found out
during a live demo. Looked completely
unprepared.

Started looking for a tool to automate this.
Found Visualping, alerts on every pixel
change, completely noisy. Found enterprise
tools at $500+/year. Nothing in between.

So I built one.

The stack

• Next.js 16 (App Router)
• Playwright for scraping
• Supabase for storage
• Resend for emails
• vercel for hosting and cron worker

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The hardest part: signal vs noise

Generic page monitoring is easy. Meaningful
change detection is hard.

A pricing page changes constantly, rotating
banners, timestamps, cookie notices, ad content.
If you alert on every pixel diff you're just
building a noise machine.

I built a classification engine that categorizes
changes before deciding whether to alert:

• PRICE_CHANGE — dollar amounts moving
• PLAN_CHANGE — plans appearing or disappearing
• FEATURE_CHANGE — features shifting between tiers
• COSMETIC — everything else (ignored)

The key insight: normalize the text before diffing. Strip dates, times, navigation text, cookie notices, social handles. Then run a line-by-line diff on what's left.

Only PRICE_CHANGE, PLAN_CHANGE, and FEATURE_CHANGE trigger an email.

Why Playwright over Puppeteer

Pricing pages are almost always JS-heavy SPAs. Puppeteer struggles with modern React apps,content loads after the initial HTML response.

Playwright with waitUntil: 'networkidle' plus a 2 second additional wait handles even the most aggressive lazy-loading. Worth the slightly heavier dependency.

The cron worker

Runs at 9am daily. Processes monitors sequentially with a 3 second delay between each — not parallel. Parallel scraping gets you rate-limited and blocked fast.

On first run: saves a baseline snapshot. On subsequent runs: diffs against the previous snapshot, classifies the change, sends alert if significant

What I'd do differently

The diff algorithm is the weakest part right now. Line-by-line text diff catches most changes but misses subtle restructuring, when a competitor moves a feature to a different plan section without changing the text, the diff doesn't catch it cleanly.

Next step is extracting structured data (plan name → price → features[]) and diffing the structure instead of raw text.

It's live and free

https://priceblind.vercel.app/

No account, no credit card. Paste a URL, get emailed when pricing changes.

Happy to answer questions about any part of the implementation, the scraping, the diff engine, or the email delivery.

What would you build differently?