Direct answer: of the 426 fetchable images in the study-99 full sweep, 423 yielded intrinsic pixel dimensions (three JPEGs keep their size marker beyond 5 MB and were not downloaded further). 15 are wider than 1920 px, 11 are wider than 3840 px and 11 exceed 8 megapixels; the largest is 5760×3840 (22.1 MP), plus one 6809×2480 (16.9 MP). The median is only 190×110 (22,496 px) — the large images sit on a few pages.
These are intrinsic dimensions, not rendered size; this study does not measure CSS layout or the bytes a device actually downloads. The 538 img src occurrences contain no srcset, so these large images have no responsive candidates.
Method: read file headers, do not decode pixels
For the 426 images that returned 200 in study 99, we requested Range: bytes=0-262143 and parsed the dimension fields of PNG, JPEG, GIF, BMP, WebP and SVG; if a JPEG SOF was not found within 256 KB, we extended to 5 MB. Three JPEGs keep their SOF beyond 5 MB (files around 23 MB) and are recorded as unknown. No pixels are decoded and no quality or copyright judgement is made.
| Item | Rule | Boundary |
|---|---|---|
| Width/height | Pixel size in the file header | Not CSS display size |
| Pixels | Width × height | Not file bytes |
| Bytes/pixel | Content-Length ÷ pixels | Depends on format and compression |
| Unknown | 3 JPEGs with SOF beyond 5 MB | Listed separately, not filled with 0 |
Result: 15 wider than 1920 px, 11 above 8 MP
| Threshold | Images | Of 423 |
|---|---|---|
| Width > 1920 px | 15 | 3.5% |
| Width > 2560 px | 12 | 2.8% |
| Width > 3840 px | 11 | 2.6% |
| Height > 1080 px | 17 | 4.0% |
| Height > 2160 px | 11 | 2.6% |
| Pixels > 1 MP | 44 | 10.4% |
| Pixels > 4 MP | 13 | 3.1% |
| Pixels > 8 MP | 11 | 2.6% |
The median is 190×110 (22,496 px), so most images are small icons or thumbnails; the tail is heavy: 44 exceed 1 MP and 11 exceed 8 MP. The maximum width is 6809 px and the maximum height 3840 px.
The eight largest
| Site | Index | Dimensions | MP | Bytes | Format |
|---|---|---|---|---|---|
| E12 | 14 | 5760×3840 | 22.1 | 1,590,080 | JPEG |
| E17 | 43 | 6809×2480 | 16.9 | 516,695 | JPEG |
| E12 | 18 | 4000×3420 | 13.7 | 2,591,172 | PNG |
| E12 | 19 | 4000×3420 | 13.7 | 3,641,012 | PNG |
| E12 | 20 | 4000×3420 | 13.7 | 4,395,921 | PNG |
| E12 | 21 | 4000×3420 | 13.7 | 5,545,658 | PNG |
| E12 | 22 | 4000×3420 | 13.7 | 4,071,857 | PNG |
| E12 | 23 | 4000×3420 | 13.7 | 3,755,475 | PNG |
The large images are concentrated: E12 has one 5760×3840 JPEG and six 4000×3420 PNGs; E17 has one 6809×2480 JPEG. Other pages have far fewer. A 14-page median hides this tail.
By format: median PNG 60×50, median JPEG 750×400
| Format | Images | Median width | Median height | Median pixels | Median bytes/pixel |
|---|---|---|---|---|---|
| PNG | 201 | 60 | 50 | 2,916 | 0.83 |
| JPEG | 162 | 750 | 400 | 284,000 | 0.38 |
| SVG | 54 | 24 | 24 | 576 | 2.00 |
| GIF | 5 | 840 | 600 | 504,000 | 3.50 |
| BMP | 1 | 556 | 113 | 62,828 | 3.00 |
Most PNGs are tiny icons (median 60×50), but the largest PNGs reach 4000×3420 and 5.5 MB; JPEG has a larger median size but a lower bytes-per-pixel. Format and dimensions together determine the download: one 5760×3840 JPEG is 1.59 MB, while several 4000×3420 PNGs are 2.6–5.5 MB.
The three unknown images: JPEGs around 23 MB
The three unmeasured JPEGs (E12 items 6, 7 and 9) are about 23.7 MB, 23.6 MB and 23.3 MB, with their SOF beyond 5 MB. They are excluded from the 423-image dimension distribution, but "unknown dimensions" does not mean "small": acceptance should record file bytes and pixel dimensions separately.
Intrinsic size is not display size
This study reads file headers only; it does not measure CSS rendering or device viewports. A 4000×3420 image may be displayed at 400 px or at full size. The 538 img src occurrences contain no srcset and no loading=lazy, so mobile has no responsive candidate and may download these large images directly. Judging the actual download requires a browser network trace, which this study did not do.
What this means for acceptance
- Add width/pixels to image acceptance. Extension and bytes alone miss 4000×3420 images.
- Set a maximum dimension. For example, content images at most 1920 px wide; this sample has 15 above 1920 and 11 above 3840.
- Prefer JPEG/WebP for large photos over PNG. The 4000×3420 PNGs are 2.6–5.5 MB each, while the 5760×3840 JPEG is 1.59 MB.
- Add srcset or size parameters. This sample has zero srcset and zero query parameters; mobile has no on-demand variant.
- Report bytes and pixels separately. Three 23 MB JPEGs have unknown dimensions; reporting only one measure misses the other.
Limits
- 423/426 known: three JPEGs keep their SOF beyond 5 MB and are unknown; their dimensions are not inferred.
- Intrinsic size: not CSS display size or actual transfer bytes; device viewport not measured.
- No quality judgement: pixels are not decoded; sharpness, compression artefacts and copyright are not judged.
- 14-page pilot: the same homepages as studies 95–99; not an industry estimate.
- Single time window: fetched 2026-11-07; no redesign recheck.
Data and reproduction
Anonymised data: equipment-homepage-image-dimensions-2026.csv (426 rows × 13 columns: site, index, URL extension, status, Content-Type, length, width, height, pixels, aspect ratio, bytes/pixel, format, error). In-repo copy: docs/research/2026-11-homepage-image-dimensions.csv.
Probe: scripts/homepage_image_dimensions_probe.py (Range header, parses PNG/JPEG/GIF/BMP/WebP/SVG); tests: scripts/test_homepage_image_dimensions_probe.py (no network, 11 tests: each format, BMP negative height, SVG viewBox, unknown/empty, URL dedup). Run:
python -m unittest scripts.test_homepage_image_dimensions_probe
Related: the homepage image-delivery pilot, the homepage HTML weight composition pilot, and the article image-delivery pilot.
Sources and definitions
- Image sample: the 426 images returning 200 in the study-99 full sweep (14 homepages, 2026-11-07).
- Dimensions: Range 0–262143 for file headers; JPEG extended to 5 MB when no SOF; full large files not downloaded.
- Measured 2026-11-07; sites anonymised.
Related: the homepage alt-copy pilot.