pdfpix

Compress PDF to 800 KB

or drop one here
Compression level
Target size
Choose a PDF file first.

800 KB is 819,200 bytes. Nobody sets a cap at 800 KB. People aim at it because the real cap is 1 MB and they want the file to clear it without argument. That headroom is worth having, and this page explains how much of it you actually need.

How to compress a PDF to 800 KB

  1. Choose the PDF

    Press Choose a PDF, or drop the file on the page. The file is read in this tab and is not sent anywhere.

  2. The target is already set

    This page opens at 800 KB, so there is nothing to type. Pick a different level, or enter your own smaller number in KB, if you want another size.

  3. Press Compress

    Four methods race: copy the pages into a fresh file, re-encode the placed images, cut each embedded font down to the glyphs the pages draw, and, only when no other method reached the target, redraw the pages as images with the text kept on top.

  4. Read the check, then download

    Every candidate is opened again and its characters are counted against the source. The page shows the size, the method that won and the characters kept before it offers the download.

The four methods are described in full, with the measurements behind them, in how it works.

Why aiming under the cap is the right move

Systems round, re-encode and wrap. A file that sits at 1,020 KB against a 1 MB cap is at the mercy of whether the receiving system counts in binary or decimal, and of whatever it adds before it stores the file. 800 KB removes that whole class of problem.

The decimal reading of 1 MB is 1,000,000 bytes and the binary reading is 1,048,576. That is a 48,576 byte disagreement, and it is exactly the width of the gap that bounces files people thought were fine.

Mail needs more headroom than a portal

Mail encodes attachments before it sends them, and the encoded form is roughly a third larger than the file on disk. Against a hard 1 MB mail limit, an 800 KB PDF travels as about 1.07 MB and still bounces. For mail, aim at 700 KB or below.

For a web upload form there is no encoding overhead, so 800 KB against a 1 MB cap is plenty of room. The compress tool takes either number; the difference is one chip.

What 800 KB costs you

Usually nothing visible. The measured points either side are a 500 KB target met on 9 of 16 cases and a 1,000 KB target met on 5 of 10. A document that reaches 1 MB almost always reaches 800 KB too, often through the same method and the same quality setting.

A 500 KB target is the next real step down if you want more margin still. The 1 MB target is there if you would rather use the whole budget and check the file against the form yourself.

Questions

Why compress to 800 KB instead of 1 MB?
Because the two readings of 1 MB differ by 48,576 bytes, and receiving systems add their own overhead. 800 KB clears every reading of the cap without a second attempt, and on most documents it costs nothing you can see.
Is 800 KB small enough for email?
For a 5 MB or 10 MB mail limit, easily. For a hard 1 MB mail limit, no. Mail encoding adds about a third, which puts an 800 KB file at roughly 1.07 MB in transit. Target 700 KB for that case.
How many bytes is 800 KB?
819,200 bytes at 1,024 bytes to the kilobyte. Since 800 KB is a self imposed margin rather than a published cap, the binary and decimal difference does not matter here the way it does at round limits.
Does aiming at 800 KB change what the tool does?
Not structurally. The same four methods race and every candidate is checked the same way. A looser target simply means an earlier method is more likely to win, which usually means nothing visible changed at all.

The other pdfpix tools

All 30 of them run in a browser tab like this one. Each reads its own output back and checks it before offering the download, and none of them needs an account.

Where to go next