How to compress an image — to an exact KB size if needed with OnyxPDF
- Drop your images (JPG, PNG or WebP) into the tool.
- For a size target, click “Compress to exact KB” and type the limit — 200 KB is the common form limit.
- Or stay in quality mode and set the quality slider (and palette colours for PNG).
- Click “Compress Images” and download the results with honest before/after sizes.
Why do it in your browser instead of uploading?
- Exact-KB mode: the form says “under 200 KB”, you type 200, the tool iterates until the output fits — then verifies the real bytes.
- No 500/month cap, no ~20-per-session web limit, no 5 MB file cap like TinyPNG’s free tier.
- Smart PNG compression: a median-cut palette encoder (the TinyPNG trick) shrinks photo PNGs several-fold instead of canvas’s barely-smaller truecolour export.
- Batch, with no upload: your photos never sit on a compression server.
Good to know (honest limits)
- Exact-KB outputs are JPEG or WebP — a PNG cannot chase a KB target losslessly, and the tool says so instead of quietly failing.
- If a target is physically unreachable at sane quality, the tool steps dimensions down and honestly reports the smallest it could reach.
- Palette PNG compression can band fine gradients at low colour counts; the slider (16–256 colours) lets you trade size for smoothness. Transparent PNGs use the truecolour path.
Frequently asked questions
How do I compress an image to exactly 200 KB (or 100 KB / 50 KB)?
Use “Compress to exact KB”, type your target, and compress. The tool binary-searches quality — and, if needed, dimensions — until the output is at or under the target, then shows you the exact final size.
Why do online forms reject my photo?
Portals cap uploads (common caps are 20–350 KB). A phone photo is usually 2–5 MB. Exact-KB compression shrinks it to just under the cap instead of you guessing quality sliders repeatedly.
Will compressing ruin my photo’s quality?
At form/upload sizes, no visible difference in normal use. In quality mode you control the trade-off with the slider; the before/after sizes are always shown honestly.
Are my images uploaded for compression?
No. Compression runs in your browser; there is no server, no account and no monthly counter.