Screen resolution dimension
The screen resolution dimension records the visitor's screen dimensions in pixels, read from the browser's screen API. It helps with responsive-design decisions, but it is coarser and more privacy-sensitive than it appears: device pixel ratio means CSS pixels differ from device pixels, common resolutions cluster heavily, and fine-grained screen metrics are a known fingerprinting input — so coarse buckets are the privacy-safe approach.
What this means
Screen resolution is the visitor's display size in pixels, read from the browser's screen.width and screen.height (or viewport equivalents). It is used to understand the range of screens your audience uses and to prioritise responsive breakpoints.
Caveats and privacy
Device pixel ratio means the CSS pixels a layout sees differ from the physical device pixels — a high-DPI phone reports a large device resolution but renders at a smaller CSS size. Resolutions also cluster around a handful of common values. Critically, precise screen metrics are a documented fingerprinting input, so reporting coarse bands (rather than exact pixel pairs) keeps the dimension useful without inflating entropy.
- Read from the browser screen/viewport API
- Device pixel ratio separates CSS pixels from device pixels
- Fine-grained values add fingerprinting entropy — bucket them
How it appears in analytics and logs
A screen resolution value is the browser-reported screen size. Read it as a banding signal for layout, not as exact hardware, and prefer bucketed ranges over precise pixel counts.
Diagnostic use case
Use screen resolution in coarse buckets to guide responsive layout decisions, avoiding fine-grained values that add fingerprinting entropy without analytical value.
What WebmasterID can help detect
WebmasterID can report coarse resolution bands for responsive decisions while deliberately avoiding the high-entropy precision that fingerprinting relies on.
Common mistakes
- Reading device resolution as the CSS layout size.
- Storing exact pixel pairs that add fingerprinting entropy.
- Treating clustered common resolutions as precise hardware data.
Privacy and accuracy notes
Fine-grained screen metrics raise fingerprinting entropy. WebmasterID prefers coarse resolution bands and does not combine screen size with other signals to identify visitors.
Related pages
- Device category: desktop, mobile, tablet
Device category groups visits into desktop, mobile, or tablet. It is derived from the user-agent string (increasingly, User-Agent Client Hints), so it is a classification, not a hardware fact. Tablets, desktop-mode mobile browsers, and foldables blur the boundaries, and the user agent can be spoofed.
- Browser dimension and its limits
The browser dimension records which browser a visit used — Chrome, Safari, Firefox, Edge, and so on. It is parsed from the user-agent string (and increasingly User-Agent Client Hints), so it is a classification, not a fact reported by the device. UA freezing, Chromium-based browsers sharing tokens, and in-app webviews are why this dimension is fuzzier than it looks.
- User agent entropy and privacy
The user-agent string packs many details — browser, version, OS, device — whose combination adds entropy that contributes to browser fingerprinting. To reduce passive tracking, browsers freeze and reduce the user agent and move high-entropy detail behind explicitly requested Client Hints. Coarse use stays privacy-safe; aggregating detail to identify users does not.
- Privacy-first analytics
Coarse resolution bands, no fingerprinting.
Sources and verification notes
Last reviewed 2026-06-24. Facts are checked against primary/official sources where available; uncertain specifics are marked “Data not yet verified” rather than guessed.