Resolutions
The Screen size card on the board shows how your page views are distributed across six display resolution bands. Each band covers a range of screen widths reported by the browser at the moment the beacon fires.
The six resolution bands
StatelessID maps the screen width reported by the browser into one of six named bands: 480p, 720p, 1080p, 2K, 4K, and 8K. The mapping is based on horizontal pixel count. Screens up to 480 pixels wide fall into the 480p band. Screens from 481 to 720 pixels wide fall into the 720p band. Screens from 721 to 1080 pixels wide fall into the 1080p band. Screens from 1081 to 2048 pixels wide fall into the 2K band. Screens from 2049 to 4096 pixels wide fall into the 4K band. Screens above 4096 pixels fall into the 8K band.
These bands are anchored to the screen's pixel width, not the browser viewport width. On high-DPI (retina) displays, the screen width in CSS pixels may be different from the physical resolution. The beacon reports the screen width in CSS pixels, which is what the bands represent.
The 480p band includes most smartphones in portrait orientation. The 720p band captures some tablets and older smartphones in landscape. The 1080p and 2K bands cover the majority of laptop and desktop monitors. 4K and 8K visits are relatively rare and usually indicate a large external monitor or a TV screen.
What resolution data tells you
The distribution across resolution bands is a signal for responsive design decisions. If 60% of your page views come from the 480p band, your site is being used mostly on smartphones, and every design and performance decision should treat mobile as the primary experience. If 70% come from 1080p and 2K, your audience is predominantly desktop.
A shift in the resolution distribution over time can indicate a change in your audience. If a campaign brought in mobile-heavy traffic but your organic baseline is desktop-heavy, you will see the distribution tilt toward 480p during the campaign window and return to its normal shape afterward.
Resolution data also matters for Core Web Vitals and load speed. Mobile devices on cellular connections tend to cluster in the slow load-speed bands. If you see high 480p traffic paired with high 3–8 s and over-8 s load counts in the Load speed card, the intersection of those two signals suggests mobile users are experiencing slow loads — even though the board does not cross-reference the two directly.
How the beacon captures resolution
The script reads the screen.width property in JavaScript at the moment the beacon fires. This reflects the device's screen width in CSS pixels at the time of page load. It does not change if the user resizes the browser window after the beacon has fired. One page load equals one resolution measurement.
Because the beacon fires once per page load, the resolution recorded is the width at load time. A user who loads your site on a tablet in portrait mode and then rotates to landscape will have their beacon recorded with the portrait width. Any subsequent page load after rotation will record the landscape width as a new beacon.
Privacy and resolution data
Screen width alone is a relatively coarse signal. StatelessID stores only the band label — 480p, 720p, and so on — not the raw pixel value. This means the stored value cannot identify a device, and two visits on completely different devices that happen to fall in the same band are indistinguishable.
The band approach also means you cannot reconstruct the exact screen size of any visit from the stored data. The 1080p band covers all widths from 721 to 1080 pixels, which includes a wide range of tablets and small laptops. The aggregate count for a band tells you how many visits came from screens in that range, nothing more.
Troubleshooting resolution data
If the Screen size card shows only Other with no named bands, all bands have fewer than five visits in the selected range. This is a privacy-floor effect on a very quiet site or a very narrow date range. Widen the range.
If the distribution looks wildly wrong — for example, 90% 8K on a site that mainly serves mobile users — check whether the script is installed on pages that serve a different audience than your main site, such as an admin panel or a status page. Those pages may have very different resolution profiles and would pull the distribution toward desktop.
Troubleshooting
If you see an unusually high fraction of 480p visits on a site you designed primarily for desktop, consider whether the script is installed on a mobile-optimised subdomain or page set that the main site's analytics do not cover. The resolution distribution reflects only the pages where the script fires.