Samsung reference
4 Galaxy S21 models compared using manufacturer panel specifications and separately published CSS observations.
Galaxy S21 (main): 360 × 800 CSS reference; DPR 3; Galaxy S21 Ultra (main): 360 × 800 CSS reference; DPR 4; Galaxy S21+ (main): 360 × 800 CSS reference; DPR 3; Galaxy S21 FE (main): CSS viewport not documented. Actual browser viewport dimensions vary with settings and browser UI.
Galaxy S21: OS family only; installed Android/One UI version varies by market and updates.
Galaxy S21 (main): Published Mobile FIRST CSS viewport/DPR, not a guaranteed default: browser chrome, display zoom, resolution and accessibility settings may change it; exact test settings are not documented.
Galaxy S21 Ultra: OS family only; installed Android/One UI version varies by market and updates.
Galaxy S21 Ultra (main): Published Mobile FIRST CSS viewport/DPR, not a guaranteed default: browser chrome, display zoom, resolution and accessibility settings may change it; exact test settings are not documented.
Galaxy S21 Ultra (main): Alternative YesViz record: 384×854 CSS px, DPR 3.75; exact display setting unreported.
Galaxy S21+: OS family only; installed Android/One UI version varies by market and updates.
Galaxy S21+ (main): Published Mobile FIRST CSS viewport/DPR, not a guaranteed default: browser chrome, display zoom, resolution and accessibility settings may change it; exact test settings are not documented.
Galaxy S21 FE: OS family only; installed Android/One UI version varies by market and updates.
Galaxy S21 FE (main): No independently verified model-and-screen-specific CSS viewport/DPR retained; null does not mean zero.
Physical panel resolution describes the display hardware. CSS reference dimensions describe a published logical screen configuration, not necessarily the visible browser window. The live viewport below reads window.innerWidth and window.innerHeight. Browser bars, page zoom, display scaling, operating system version and folding can change that viewport. Never identify a phone solely by its CSS width or device pixel ratio.
We record physical specifications from manufacturer documentation, and CSS dimensions only when a separate technical reference explicitly documents them. We do not divide a native panel resolution by an assumed pixel ratio to invent a viewport. Missing observations are marked Not documented. A published reference is not a measurement of your own phone; test your actual browser before relying on a breakpoint.
Landscape browser viewport values need their own observations: simply swapping portrait dimensions ignores browser controls, cutouts, safe areas and system insets. When a landscape measurement is missing we leave it undocumented. A rotated reference rectangle can help with a layout simulation, but is not an independently verified landscape viewport.
Use content-driven breakpoints rather than device-detection media queries. Test narrow widths first, then gradually expand the browser until the layout needs to change. Images need sufficient pixel density for the actual rendered size; devicePixelRatio can change with zoom and system display settings. On foldables, test cover and inner screens separately and resize while the page is open.
Manufacturer-confirmed panel resolution describes physical hardware only. Independently measured CSS viewport requires a dated measurement method, browser and OS context. Documented third-party viewport reference means a source explicitly publishes the values, but not necessarily that its device settings or measurement method are known. Emulator configurations are testing presets, never measurements of a physical phone in its default setup. Unknown or conflicting values stay visibly qualified.
A manufacturer-backed panel does not verify a whole device. Missing browser version, OS version, zoom and display scaling remain unknown. PPI is cited or calculated from panel pixels and diagonal inches, never used to invent CSS measurements. Incomplete entries do not automatically receive indexable articles. Coverage includes only the listed models and display states.
Layout viewport is the page layout area reported by window.innerWidth and innerHeight. Visual viewport is the currently visible page area; pinch zoom or the keyboard can change it. Screen dimensions are logical CSS pixels, not native panel resolution. Device pixel ratio and visual viewport scale are separate readings, not interchangeable zoom percentages.
Copy Measurement includes a fresh UTC timestamp and the available browser readings. Unavailable visual viewport values remain unavailable. Readings stay local and are not automatically stored, submitted or added to the catalog. Neither viewport nor user agent reliably identifies a phone model.
| Model / display | Year | Diagonal | Physical panel | CSS portrait reference | Landscape viewport | DPR | PPI | Panel evidence | Viewport evidence | Fold state | CSS configuration | CSS source / checked |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Galaxy S21 — main | 2021 | 6.2″ | 1080 × 2400 | 360 × 800 | Not documented | 3× | 421 | Manufacturer-confirmed panel resolution | Documented third-party viewport reference | Not applicable | Published portrait CSS screen reference; browser/OS version, resolution mode and display zoom were not documented by the source. Not a verified real-device default or window.innerHeight measurement. | https://www.webmobilefirst.com/en/devices/brands/samsung/ · 2026-10-19 |
| Galaxy S21 Ultra — main | 2021 | 6.8″ | 1440 × 3200 | 360 × 800 | Not documented | 4× | 515 | Manufacturer-confirmed panel resolution | Documented third-party viewport reference | Not applicable | Published portrait CSS screen reference; browser/OS version, resolution mode and display zoom were not documented by the source. Not a verified real-device default or window.innerHeight measurement. | https://www.webmobilefirst.com/en/devices/brands/samsung/ · 2026-10-19 |
| Galaxy S21+ — main | 2021 | 6.7″ | 1080 × 2400 | 360 × 800 | Not documented | 3× | 394 | Manufacturer-confirmed panel resolution | Documented third-party viewport reference | Not applicable | Published portrait CSS screen reference; browser/OS version, resolution mode and display zoom were not documented by the source. Not a verified real-device default or window.innerHeight measurement. | https://www.webmobilefirst.com/en/devices/brands/samsung/ · 2026-10-19 |
| Galaxy S21 FE — main | 2022 | 6.4″ | 1080 × 2400 | Not documented | Not documented | Not documented | 411 | Manufacturer-confirmed panel resolution | Unknown / insufficient evidence | Not applicable | Not documented | Not documented |