Spyglass Contrast Checker by Deneb

Spyglass is a contrast analysis tool that runs as a floating overlay on any webpage. Click the extension icon, then use the Element Picker to instantly capture foreground and background colors from any element — including hover states. Spyglass supports both WCAG 2.x contrast ratios and the APCA (Advanced Perceptual Contrast Algorithm) used in WCAG 3, letting you evaluate color pairs against the standard that matters for your project.

For text rendered over images or gradients, the Overlay Picker performs pixel-level analysis across the full text region, reporting a min/max contrast range rather than a single value.

Features:
— Element Picker with resting and hover state modes
— Overlay Picker with pixel-level contrast sampling for images and gradients
— WCAG and APCA algorithm toggle
— Live color tweak controls with suggested passing alternatives
— Preview pane showing your color pair at normal and large text sizes
— AA and AAA pass/fail grid
— Drag-and-drop positioning
— Works on any webpage without sending data anywhere

No accounts. No telemetry. No external requests. All analysis runs locally in the browser.