Reduce image size in KB — pick any target
Type any KB target and get an image that fits it: the encoder searches quality, then dimensions, and shows every step and the final byte count.
- Runs in your browser
- Files are never uploaded
- Free, no account
1 KB = 1024 bytes, the same arithmetic your operating system uses.
Only kicks in when quality 5 still overshoots.
Type the number the form gave you
Every other size-reduction page assumes a target. This one asks you for it, because the limits in the wild are arbitrary: 35 KB, 80 KB, 240 KB, 3 MB. Put the number in, press compress, and the encoder searches for the highest-quality file that fits under it — then shows you the exact byte count it achieved and every attempt it made along the way.
Limits you are likely to meet
| Where | Typical limit | Practical advice |
|---|---|---|
| Exam and recruitment portals | 20–50 KB photo, 10–20 KB signature | Crop tightly first; set the pixel dimensions they specify in the width cap |
| Visa and passport uploads | 50 KB – 1 MB | Combine with Passport Photo Maker for the exact crop |
| Web pages and blogs | 100–300 KB | Cap the width at 1200–1920 px; prefer WebP |
| Email attachments | 500 KB – 2 MB each | Remember base64 adds about a third in transit |
| Marketplace and classified listings | 1–5 MB | Rarely tight; 1 MB keeps full resolution |
| Forum avatars | 50–200 KB, fixed pixel size | Set the width cap to their pixel size first |
How the search works
- Any width cap you set is applied first, so the search operates on the dimensions you want.
- The image is encoded at quality 92 and measured. If it fits, you keep that quality — the tool never compresses more than it has to.
- Otherwise it binary-searches the quality range over about nine encodes, keeping the highest setting that comes in under the target.
- If even the lowest quality overshoots, it searches the pixel scale instead, using a Lanczos3 resample, for up to eight more attempts.
- If nothing fits, you still get the smallest file it produced, plus an explicit warning — never a silent failure.
Choosing a target when you have a range
Aim at the top of it. “Between 20 KB and 50 KB” means submit 49 KB, not 25: the largest allowed file is the sharpest one you can hand in, and there is no benefit to being well under. Some portals do enforce a minimum as well, usually to reject blank or placeholder images — the achieved size is printed in the result so you can check both ends.
KB, KiB and the 2% margin
We treat 1 KB as 1024 bytes and aim 2% below the target. That margin matters more often than you would think: some validators compare the base64-encoded length rather than the raw one, some count the multipart form overhead, and all of them reject a file a single byte over. If you need the 1000-byte interpretation instead, a target of 100 KB here yields roughly 100,000 bytes anyway, so both readings pass.
Getting the best result at any target
- Crop before you compress. Fewer pixels is the cheapest quality you will ever buy.
- Cap the width. Especially for anything that will be displayed small.
- Pick WebP where allowed. Roughly a third smaller than JPEG at the same visual quality.
- Do not double-compress. Start from your original file every time; JPEG generation loss compounds.
- Check the attempt table. If the chosen quality is above 90 your target is generous; under 55 and you should crop instead.
Batch, ZIP and no quotas
Drop in any number of files: each gets its own search to the same target, with a per-file progress row and individual or ZIP download. There is no daily limit, no signup, no watermark and no upload — the whole loop runs on your CPU, which is the only reason an exact byte target is practical in the first place.
Fixed targets
20 KB · 50 KB · 100 KB · 200 KB · 500 KB · 1 MB. For a plain quality slider, use Compress Image; to change pixel dimensions directly, use Resize Image.
Questions
What target should I choose?
Whatever the form in front of you demands. If it gives a range, aim at the top of it — the largest allowed file is the sharpest one you can submit. If it gives no number, 200 KB is a sensible default for a web-quality photo.
How many attempts does the search take?
Ten for the quality pass and up to eight more for the resize pass. Each is a full local encode, which is why the whole search finishes in about a second on a normal laptop and why every attempt is listed in the result.
Can I set a maximum width at the same time?
Yes. The width cap is applied before the search begins, which is usually the single most effective way to reach a small target while keeping the picture clean.
What if the target is impossible?
You still get a file — the smallest the tool could produce — plus a clear warning that the target was not met, so you know to crop the image or raise the limit rather than being left guessing.