Free tool · JPEG output · Runs in your browser
Compress an image to 500 KB
Short answer
Choose your image and the tool finds the best JPEG that fits 500 KB (512,000 bytes). On our test images it kept 2 of 4 at full size and shrank 2: the 3.1 MB photo became 1902 × 1920 at 76% quality (483 KB), and the 733 KB portrait 2122 × 2644 (493 KB). Quality alone was enough for all four. Nothing is uploaded.
Exact selected target: 512,000 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 500 KB target means 512,000 bytes (1 KB is 1,024 bytes in this tool). The results landed between 95% and 99% of it, never over.
- Photo, 3840 × 3877: quality alone reached 452 KB at 16%, SSIM 0.73; with shrinking, 1902 × 1920 at 76% and SSIM 0.91.
- Portrait, 2122 × 2644: quality alone reached 493 KB at 70%, SSIM 0.95; with shrinking, 2122 × 2644 at 70%, SSIM 0.95.
- Document scan: 3827 × 1588 (full size) at 61%. Graphic: 2186 × 2207 at 78%.
- The smallest picture in the set at this target was 1902 × 1920 (the photo).
What 500 KB means for a picture
500 KB is 512,000 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 | 483 KB | 1902 × 1920 | 1.08 |
| Portrait | 493 KB | 2122 × 2644 | 0.72 |
| Document scan | 477 KB | 3827 × 1588 | 0.64 |
| Graphic (PNG) | 488 KB | 2186 × 2207 | 0.83 |
For 2 of the 4 images the search had to shrink the picture to keep the quality at a sensible level; the smallest result was 1902 × 1920 pixels.
Measured: 500 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 | 452 KB, 16%, SSIM 0.73 | 1902 × 1920, 76%, 483 KB, SSIM 0.91 |
| Portrait, 2122 × 2644 | 715.7 KB | 493 KB, 70%, SSIM 0.95 | 2122 × 2644, 70%, 493 KB, SSIM 0.95 |
| Document scan, 3827 × 1588 | 1.30 MB | 477 KB, 61%, SSIM 0.93 | 3827 × 1588, 61%, 477 KB, SSIM 0.93 |
| Graphic (PNG), 5380 × 5432 | 17.99 MB | 488 KB, 11%, SSIM 0.87 | 2186 × 2207, 78%, 488 KB, SSIM 0.92 |
At this size, quality alone met the target for all four images.
What is kept and what is saved at 500 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 | 483 KB | 84.0% | 24.5% |
| Portrait | 715.7 KB | 493 KB | 31.1% | 100% |
| Document scan | 1.30 MB | 477 KB | 64.0% | 100% |
| Graphic (PNG) | 17.99 MB | 488 KB | 97.3% | 16.5% |
Shrinking changed the score by +0.18, +0.00, +0.00, +0.04 (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 500 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 500 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 100 KBCompress an image to 200 KB
Questions people ask
How do I compress an image to 500 KB?
Choose 500 KB (or type 500 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 500 KB. In our test 2 of 4 images were shrunk; the smallest was 1902 × 1920.
Is the result exactly 500 KB?
No. It stays at or under 512,000 bytes and, in our tests, within 5% 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.