Screenshots & Visual Regression

Two related but distinct features: failure screenshots capture what your site looked like when it went down. Visual regression compares each check against a baseline and flags pixel-level changes.

Failure screenshots

When a monitor flips to down or degraded, Happy Uptime triggers a Cloudflare Browser Rendering session against the monitor's URL, captures a PNG at three viewports (desktop / tablet / mobile), and stores it in R2 keyed by screenshots/{monitorId}/{checkResultId}.png.

You see the screenshot:

• In the alert payload (Slack message includes a thumbnail link)
• On the monitor detail page in the dashboard
• Via GET /screenshots?monitor_id=…

Storage retention: 30 days for failure screenshots. Baselines are kept indefinitely.

Visual regression

Enable screenshot_compare: true on the monitor, capture a baseline (one click in the dashboard), and every successful check thereafter:

1. Captures a fresh screenshot.
2. Computes a perceptual hash (pHash).
3. Compares against the baseline's hash.
4. If the diff exceeds screenshot_threshold (default 0.05, range 0–1), fires a visual_regression alert.

Use cases:

• Marketing site got hijacked? Visual regression catches it before keyword monitoring.
• A deploy accidentally pushed staging banners to prod? Regression catches it.
• A vendor (e.g. payment provider iframe) breaks visually but still returns 200? Regression catches it.

Per-viewport baselines

Capture separate baselines for desktop/tablet/mobile. Useful when responsive breakpoints render differently and you want to detect changes only at one breakpoint.

Quick links