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OS Authority

Compress a PDF to under 500 KB

500 KB leaves room for good-quality scans. Your PDF comes back under the limit, as sharp as that size allows.

Your PDF is processed on this device and never uploaded. We don't see, store or log your files.

Common sizes

How it works

  1. Tap Choose file and pick your PDF.
  2. Tap Compress PDF. The tool finds the gentlest compression that fits under 500 KB.
  3. Download or share the new PDF, and check the size shown in the result.

Why compress here

Your PDF never leaves your phone or computer, which matters for certificates, IDs and statements you upload to forms. It is free, with no watermark and no sign-up, and the text in your PDF stays sharp: only images are re-compressed.

How the size is reached

Text, fonts and vector drawings in a PDF are already compact, so the size comes almost entirely from images (scans and photos). The tool re-compresses them step by step, from gentle (2400 pixels, high quality) to strong (500 pixels), and keeps the gentlest step that fits under your limit, trying at most 4 steps. Colours are never changed. A 10-page phone scan of 5–10 MB usually fits in 1 MB with sharp text; fitting it in 200 KB means about 20 KB per page, which is readable but softer.

When the limit can't be reached

A PDF made from Word or a web page is mostly text and may already be 100–300 KB; it can't shrink much further. If even the strongest step is above your limit, you still get the smallest version we could make, and the result says how close it came. Splitting the PDF into parts (Split PDF) or removing pages you don't need (Organize PDF) usually solves it.

Frequently asked questions

Will photos inside the PDF still look good?

At 500 KB, a few photos keep good quality; many photos are reduced more to fit.

Is 1 MB 1,000 KB or 1,024 KB?

Sites count it both ways. We use 1,000: a "1 MB" file here is at most 1,000,000 bytes, so it also passes a form that counts 1,048,576.

Is my PDF uploaded?

No. Everything happens in your browser on your own device.

Last reviewed: October 1, 2026

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