Government portals, university application forms, job sites and email attachments all love to impose exact file-size ceilings: 100KB, 200KB, 500KB, 1MB. The problem: a photo straight out of your phone is 3–8MB, and most "compress online" sites make you upload personal pictures to a stranger's server, then guess at quality sliders until you're under the limit.
This guide shows how to hit an exact KB target locally in your browser, in under a minute — with the file never leaving your device.
Why hitting an exact size is tricky
JPEG size isn't linear. Reducing quality from 90 to 80 might save 40%; going from 60 to 50 might save only 10%. Dimensions matter even more: halving width and height cuts the file to roughly a quarter. That's why manually sliding a quality bar is frustrating — you're searching a two-dimensional space (quality × dimensions) by trial and error.
The smart approach is a target-size search: the tool binary-searches quality automatically until the output lands just under your limit, at the highest possible quality. That's exactly what the target-size tools on this site do.
Step by step: compress to an exact target
1. Open the tool for your limit
Pick the preset matching your requirement — Compress to 100KB, Compress to 1MB, or open the JPG Compressor and type any custom target from 10KB to 10MB.
2. Drop your images
Drag one or fifty files onto the dropzone. Batch is fine — each file is compressed independently to the same target. Nothing uploads; you can even disconnect your Wi-Fi first to prove it.
3. Set the target and let the search run
Enter your ceiling in KB. The tool tries successive quality levels, measures the real encoded size, and converges on the highest quality that fits under the limit. You get the smallest visual loss the format allows for that size.
4. Download — one by one or as a ZIP
Check the result size shown on each card, then download individually or grab everything as a single ZIP.
If the target is physically impossible
A 100KB limit on a 4000×3000 photo means aggressive compression. Two options that preserve perceived quality better than a quality crash:
- Resize first. If the image will be viewed at 800×600, don't compress a 4000×3000 original. Use the Bulk Image Resizer to bring dimensions down — smaller dimensions need far less compression.
- Lower the target slightly below the limit (e.g. 95KB for a 100KB cap). Some portals measure differently, and a small buffer avoids a rejection loop.
Which format should the output be?
- JPG — the universal choice for photos and form uploads. Smallest size per quality level.
- PNG — only when transparency or sharp text must survive. PNG compresses poorly for photos; expect to resize dimensions to hit a small target.
- WebP — 25–35% smaller than JPG at equal quality, but only use it if the receiving system accepts it (modern browsers and most portals do; some government forms don't).
FAQ
Will the compressed image look bad?
At reasonable targets (100KB+ for a photo viewed at screen size) the difference is invisible. The target-size search always keeps quality as high as the limit allows, instead of crashing quality to be safe.
Is there a file count or size limit?
No. Processing happens on your device, so the only limit is your RAM. People routinely compress folders of hundreds of images in one session.
Are my documents or ID photos uploaded anywhere?
No — and this matters most precisely for these files. Everything runs in your browser via JavaScript and WebAssembly. Verify it: open DevTools → Network, compress a file, and watch zero requests appear.
Why is my output slightly under the target rather than exactly it?
The search stops as soon as the size fits under the limit — the gap is your safety margin. Re-run with a higher custom target if you want to use more of the budget.
Ready to hit your limit? Open the 100KB compressor for form uploads, or the Bulk Image Compressor when a whole folder needs shrinking. For the theory behind why some images compress better than others, read How Image Compression Works.