pdfviz

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 publishes 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 a second attempt. That headroom is worth having, and this page explains how much of it you actually need and how pdfviz gets you there without ever uploading the file.

How to compress a PDF to 800 KB online

  1. Choose the PDF

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

  2. The target is already set

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

  3. Press Compress

    Four methods race against each other: 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. The whole process runs in your browser through WebAssembly, which means your file is never uploaded and no account is needed.

Why aiming under the 1 MB 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 extra bytes it adds before it stores the file. Aiming at 800 KB removes that whole class of problem in one step.

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. An 800 KB target sits well below both readings, so the file clears the cap no matter which arithmetic the server uses.

This matters most for government portals, insurance claim forms, and job application sites. These systems rarely explain which counting method they use, and they usually reject files silently with a generic error. Aiming 20% under the cap is the cheapest insurance against that.

Mail needs more headroom than a web 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 on the target size row. You can also type any custom value in the KB field.

If you are not sure which limit applies, compress to 700 KB and the file clears both mail and web caps. The quality cost at that level is invisible on text documents and minor on a one or two page scan.

What 800 KB costs you in quality

Usually nothing visible. The bench ran 500 KB on a six-page scan and landed at 693.2 KB from 1,191.5 KB, and 1,024 KB on the same file at 896.9 KB. A document that reaches 1 MB usually reaches 800 KB too, often through the same method and the same quality setting.

Text documents are the easy case. Font subsetting and a structural rebuild often bring a text PDF under 800 KB without touching a single pixel, and the output renders as sharp as the original at any zoom. Scanned pages are the harder case, and at 800 KB a one or two page scan stays readable while a longer scan may need a tighter 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. Both pages use the same engine and the same verification checks.

Real use cases for an 800 KB target

Job application portals that cap uploads at 1 MB. Aiming at 800 KB means the file clears the cap even if the server counts in decimal and adds its own wrapper bytes.

Insurance claim forms that reject files silently when they sit too close to the limit. The 20% headroom is enough to avoid a second round of guessing.

Government visa and tax uploads where the form gives a 1 MB limit but the backend enforces it strictly. 800 KB is the safe distance that clears every reading of the rule.

Questions about compressing a PDF to 800 KB

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 by typing 700 in the KB field.
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.
Will my text stay selectable after compression?
Yes. Text retention is checked on every candidate. The output is re-opened, its characters are read back and compared with the source, and anything below 98% of the non-space characters is refused.
Can I compress to 800 KB on my phone?
Yes. Files this size are well inside what a phone browser handles, and the compression runs in the tab exactly as it does on a desktop. The file is read in this browser tab and is not sent to any server.

The other pdfviz tools

They all 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