100KB JPG compression test

Job portals, school forms, and CMS fields still reject files over 100KB. We ran the live Compress JPG to 100KB tool on eight photographs. 8 of 8 outputs met the ceiling (102,400 bytes or less).

Ran: 5 October 2026 Ceiling: 100 × 1024 bytes Met: 8 / 8

Chart of eight photographs compressed to under 100KB with original and output file sizes — Each output bar is the generated file. The dashed line is 100KB (102,400 bytes).

What “under 100KB” means here

The tool compares generated bytes to 100 × 1024. That is 102,400 bytes. A 99 KB label is a formatted view of a file that already passed. We do not call that file “exactly 100KB”.

Method

Same eight source JPEGs as the quality-first test. One pass each through compress-jpg-to-100kb. The encoder may lower JPEG quality and, if needed, reduce pixel dimensions. We recorded bytes, dimensions, and whether the ceiling was met. Forest is the heaviest source in the set (1.09 MB).

Results

Subject	Original	Output	Pixels in	Pixels out	Change	Ceiling
Alpine	503 KB	99 KB	2400×1600	1920×1280	80.3% smaller	Met
Coast	448 KB	99.8 KB	2400×1595	1920×1276	77.8% smaller	Met
Forest	1.09 MB	98 KB	2400×1598	1200×799	91.3% smaller	Met
City	730 KB	99.4 KB	2400×1600	1440×960	86.4% smaller	Met
Ceramic	293 KB	98.9 KB	2400×1600	2400×1600	66.2% smaller	Met
Books	406 KB	99.3 KB	2400×1551	1920×1241	75.5% smaller	Met
Flower	502 KB	99.4 KB	2400×1601	1920×1281	80.2% smaller	Met
Watch	106 KB	99.9 KB	2400×1744	2400×1744	5.4% smaller	Met

What changed besides bytes

6 of 8 outputs used fewer pixels than the source. Forest dropped from 2400×1598 to 1200×799. City went to 1440×960. Ceramic stayed 2400×1600 and still landed at 98.9 KB. That spread matters: a detailed landscape needed a smaller raster, a flatter still life did not.

Alpine’s generated file was 101,407 bytes (99 KB). That is under the ceiling and about 80% lighter than the 503 KB source. The download name in verification was alpine-compressed-to-100kb.jpg.

Practical conclusion

If a form says 100KB, use the target tool, not a generic quality slider. Expect some photos to lose pixels. Check the result card: it will say whether the ceiling was met and show the real byte label. Sibling ceilings such as 50KB and 200KB follow the same rule with different byte caps.

Limits

This is one engine, one ceiling, eight photos. Screenshots and documents may need more pixel reduction. We did not collect opinion scores on softness. A source already under 100KB can still be rewritten; city started at 730 KB, not under the cap, so this set does not show the “already small” case.

Technical reference

JPEG remains the common upload format for photographs on the public web. MDN documents the type, extensions, and typical use: MDN image file type guide. For page-weight guidance, see web.dev Learn Images.