DOMRect Fingerprinting

DOMRect fingerprinting measures getBoundingClientRect() precision on hidden elements. Sub-pixel rendering differences between browsers and OS font engines produce unique measurement values.

How it works

Neoprint creates 3 hidden elements with specific CSS properties (font sizes with decimal values, fractional padding, small rotation transforms) and reads their bounding rectangles.

The sub-pixel values of x, y, width, and height differ based on:

• Font rendering engine (Core Text vs DirectWrite vs FreeType)
• Sub-pixel anti-aliasing settings
• Display scaling factor
• Browser layout engine rounding

Entropy and stability

Property	Value
Entropy	~6 bits
Stability	0.75
Typical duration	<1ms

Excluded in privacy mode.

Usage

const fp = await neoprint.get({ collectors: ['domRect'] })
const rects = fp.components.domRect.value
// [{ x: -9999, y: -9996.227, width: 187.617, height: 19.453 }, ...]