Compress an Image to Under 100 KB
A 100 KB ceiling, reached by searching quality rather than guessing it.
Who asks for a 100 KB limit
The most common limit on the web: online form uploads, scanned document attachments, job applications, visa portals and student portals.
What 100 KB buys you in pixels
A workable ceiling for a 100 KB photograph is around 900 pixels on the long edge at a quality that still looks like a photograph rather than a mosaic. That figure is empirical: it comes from how much high-frequency detail survives compression at that byte budget, and it moves up for images with large flat areas and down for images full of foliage, fabric or hair.
| Long edge | What to expect at 100 KB |
|---|---|
| Under 540 px | Comfortable — the quality search will settle in the high end of the range |
| 540–900 px | Workable — expect mid-range quality, check gradients for banding |
| Over 1350 px | Resize down first, or the target cannot be met without visible damage |
100 KB is generous enough that quality alone is usually sufficient — with a 900-pixel image the search typically lands between quality 55 and 75. Check for text sharpness if the image is a document scan.
Generous enough that quality alone is sufficient
At one hundred kilobytes a 900-pixel image typically settles between quality 55 and 75, which is inside the range where JPEG artefacts are hard to see at ordinary viewing distance. This is the most frequently quoted limit on the web, and the one where switching the output to WebP buys the largest visible improvement at the same byte count.
Why this runs in your browser
The file is read from your disk by the browser, decoded with the browser's own codecs, and re-encoded in this tab. No upload request is made, nothing is queued on a server, and closing the tab leaves no copy anywhere. You can verify this in the network panel while it works.
How to use it
- Drop the image on the drop zone.
- Set the target size to 100 KB.
- Let the quality search run — it reports the quality level it settled on.
- Check the resulting file is at or under 100 KB, then download.
Worth knowing
- Target 100 KB permits roughly 900 pixels on the long edge at photographic quality.
- The quality search encodes repeatedly and keeps the highest quality that fits.
- Image content, not just dimensions, determines how far the quality can be pushed.
- Switching to WebP at the same 100 KB budget usually looks visibly better than JPEG.
Limitations
- Very tight targets require resizing as well as compressing — compression alone has a floor.
- Downscaling permanently discards pixels; keep the original as your archive copy.
- Re-compressing an already-compressed file spends quality twice.
- Some portals also check pixel dimensions and file format, not just the byte count.