Free tool · JPEG output · Runs in your browser
Compress an image to 100 KB
Short answer
Choose your image and the tool finds the best JPEG that fits 100 KB (102,400 bytes). On our test images it kept 0 of 4 at full size and shrank 4: the 3.1 MB photo became 762 × 769 at 76% quality (96 KB), and the 733 KB portrait 862 × 1074 (93 KB). Quality alone missed the target on 3 of 4. Nothing is uploaded.
Exact selected target: 102,400 bytes. These existing KB controls use 1,024 bytes per unit; a decimal search preset retains its exact byte count.
Choose an image after setting the target.
Output is JPEG, because quality-versus-size can be searched reliably for it. The result may be below or above the target; the actual size and any unreachable target are reported. An exact byte count cannot be promised. Quality is searched first; the picture is shrunk only when quality alone cannot reach the target, and the result list shows the new size. Untick the option to keep the dimensions and trade quality only.
Key takeaways
- A 100 KB target means 102,400 bytes (1 KB is 1,024 bytes in this tool). The results landed between 93% and 97% of it, never over.
- Photo, 3840 × 3877: quality alone could not get below 185 KB; with shrinking, 762 × 769 at 76% and SSIM 0.93.
- Portrait, 2122 × 2644: quality alone reached 96 KB at 16%, SSIM 0.84; with shrinking, 862 × 1074 at 76%, SSIM 0.91.
- Document scan: 1271 × 527 at 76%. Graphic: 748 × 755 at 76%.
- The smallest picture in the set at this target was 748 × 755 (the graphic (png)).
What 100 KB means for a picture
100 KB is 102,400 bytes. The way to read it is in bits per pixel: the same budget spread over more pixels means each pixel gets fewer bits and the picture gets blockier. The table shows what the search chose for each image.
| Image | Result | Pixels | Bits per pixel |
|---|---|---|---|
| Photo | 96 KB | 762 × 769 | 1.35 |
| Portrait | 93 KB | 862 × 1074 | 0.82 |
| Document scan | 97 KB | 1271 × 527 | 1.19 |
| Graphic (PNG) | 96 KB | 748 × 755 | 1.40 |
For 4 of the 4 images the search had to shrink the picture to keep the quality at a sensible level; the smallest result was 748 × 755 pixels.
Measured: 100 KB with and without shrinking
Measured in headless Chromium with the browser's own canvas JPEG encoder, the way the tools draw: a white background, then toBlob at the quality given. Five public domain images: a 3840 × 3877 photo (3.1 MB), a 2122 × 2644 portrait (733 KB), a 3827 × 1588 handwritten document scan (1.36 MB), a 5380 × 5432 PNG graphic with transparency (18.9 MB) and a small 441 × 517 JPEG (66.6 KB). SSIM compares each result with the original at the result's own size, so 1.0 would be identical. Other browsers use their own encoders, so sizes can differ.
| Image | Original | Quality only | Quality and size |
|---|---|---|---|
| Photo, 3840 × 3877 | 2.96 MB | 185 KB (over), 5%, SSIM 0.68 | 762 × 769, 76%, 96 KB, SSIM 0.93 |
| Portrait, 2122 × 2644 | 715.7 KB | 96 KB, 16%, SSIM 0.84 | 862 × 1074, 76%, 93 KB, SSIM 0.91 |
| Document scan, 3827 × 1588 | 1.30 MB | 101 KB (over), 5%, SSIM 0.84 | 1271 × 527, 76%, 97 KB, SSIM 0.93 |
| Graphic (PNG), 5380 × 5432 | 17.99 MB | 307 KB (over), 5%, SSIM 0.55 | 748 × 755, 76%, 96 KB, SSIM 0.89 |
With quality alone, photo, document scan, graphic (png) missed the target even at the lowest quality, which is why the tool shrinks the picture by default.
What is kept and what is saved at 100 KB
The share of pixels kept and the share of bytes saved, with the shrink option on. A picture that keeps a quarter of its pixels has half the width and half the height.
| Image | Original | Result | Smaller by | Pixels kept |
|---|---|---|---|---|
| Photo | 2.96 MB | 96 KB | 96.8% | 3.9% |
| Portrait | 715.7 KB | 93 KB | 87.0% | 16.5% |
| Document scan | 1.30 MB | 97 KB | 92.7% | 11.0% |
| Graphic (PNG) | 17.99 MB | 96 KB | 99.5% | 1.9% |
Shrinking changed the score by +0.25, +0.07, +0.08, +0.35 (photo, portrait, document, graphic). The largest gains came where quality alone had to drop very low to fit.
Before you upload it
- Check the destination's own limits. If it asks for pixel dimensions as well as 100 KB, resize first and then compress.
- Look at the result at the size it will be shown. SSIM says the picture is a faithful smaller copy, not that a face is recognizable or text is readable.
- Keep your original. Compress a copy.
- If 100 KB is a limit and the file is just under it, leave a little room: some systems count a file's size differently.
Free tools:The target size tool, any sizeCompress an image with a sliderCompress an image to 20 KBCompress an image to 50 KBCompress an image to 200 KBCompress an image to 500 KB
Questions people ask
How do I compress an image to 100 KB?
Choose 100 KB (or type 100 KB) in the target size tool and add your image. It searches quality and shrinks the picture only if it has to.
Will my picture be smaller in pixels?
Often, at 100 KB. In our test 4 of 4 images were shrunk; the smallest was 748 × 755.
Is the result exactly 100 KB?
No. It stays at or under 102,400 bytes and, in our tests, within 7% below it at most.
What happens to a PNG?
It becomes a JPEG on a white background; transparency is lost.
Can I keep the original dimensions?
Yes. Untick the shrink option. The tool then trades quality only, and says if the target cannot be reached.
Why does a document or text image look worse at small sizes?
JPEG softens sharp edges, and a small picture has fewer pixels for each letter. Check readability before you send it.
Is my image uploaded?
No. It stays in your browser.
Related
Sources and how we checked
- MDN: HTMLCanvasElement.toBlob() (read 2026-10-09)
- MDN: CanvasRenderingContext2D.imageSmoothingQuality (read 2026-10-09)
- Wikimedia Commons: NASA, Portrait of Neil Armstrong (public domain); the other test images are NASA public domain files and the Bliss copy of the Gettysburg Address (read 2026-10-09)
Reviewed October 9, 2026. The measurements ran the tool's own code in headless Chromium with the browser's canvas JPEG encoder. The script and the results are in data/seo/hub/evidence/2026-10-09/image.