How to compress a PDF to 100 KB (or 200 KB)
Updated
Contents
To compress a PDF to 100 KB, open Compress PDF, add the file, and in the “Deep image compression (secure server)” panel choose a “Target size” of 100 KB — or 200 KB, 500 KB, or 1 MB, or “Custom” for a number of KB of your own. Then press Compress images on our server. Our server starts at your Quality setting, lowers the resolution of the images step by step, as far as Extreme, and gives back the highest-quality version that fits.
Whether a file can get that small depends on what is in it. A scan, or a phone photo of a page, is mostly picture, and picture resolution is what this lowers, so such files often shrink a long way. A PDF that is mostly typed text, or whose size comes from its fonts, may hardly shrink at all; then the panel tells you the smallest file it could make, and you can still download it.
This step uploads your file to our server; the size breakdown and the lossless copy on the same page run in your browser. Our privacy policy says the uploaded file is deleted when the job ends, the result can be downloaded for 60 minutes, and the stored copy is erased by a daily storage rule some time after it is 1 day old.
Step by step
- 1Open the Compress PDF tool and drop your PDF on the box, or click it to pick one. Its size breakdown appears first.
- 2In the “Deep image compression (secure server)” panel, keep the Quality at Balanced or pick another. It is the best quality our server will try; with a target it only goes down from there.
- 3Under “Target size”, choose 100 KB, 200 KB, 500 KB, or 1 MB, or choose “Custom” and type a whole number of KB. A size your file is already under cannot be chosen.
- 4Press Compress images on our server, which uploads your file. A run with a target can take longer, because each step down is another run.
- 5Read the line on the result. “Now 184.0 KB — under your 200 KB target.” means it fits: press Download compressed PDF.
- 6If the line says the file is above your target, tick “Grayscale” and run again, or make the document shorter with Split PDF or Delete Pages first.
How the target is reached
Our server makes the file at your Quality setting first, then at each lower resolution in turn, as far as Extreme, and stops at the first one at or under the target: the sharpest version that fits. If none fits, it gives you the smallest file it made, with a line saying it is above your target.
A lower resolution usually makes a smaller file, but not always. For each picture, the program that does the work chooses how to store it, and at a lower setting it can choose a way that takes more room. So the server measures every file it makes rather than assuming, and a run where nothing fits tries every setting before it answers, which takes longer.
Only the pictures in the file are made smaller. Typed text and drawn lines are not pictures, so they stay as sharp as before, and they are also why a text-heavy PDF cannot be squeezed much. The server checks that the result opens as a PDF and, when it can count them, that no page went missing.
Colour is kept. The server never turns pages gray to reach a size: it does that only when you tick “Grayscale”, and gray pages are often much smaller.
How big is 100 KB, here and on the form you are filling in
On this page 1 KB is 1,024 bytes, so a 100 KB target means at most 102,400 bytes — the same unit every size on the page is shown in. Some upload portals count 1 KB as 1,000 bytes instead. If yours does, and is strict, choose “Custom” and enter 97 KB, which is under 100,000 bytes.
The file usually comes back a little under your target rather than exactly on it, because the server stops at the first version that fits.
When the file will not fit
A target can be out of reach for a long document full of photos, or for a document that is mostly text. Running again with “Grayscale” ticked often helps a colour scan. Otherwise, make the document shorter: Split PDF can cut it into parts that each fit, and Delete Pages can drop pages the form does not need.
Your original is never changed. Each run starts from the file you added, so you can try a different target or setting as often as you like. The per-file cap is 100 MB.
Common questions
Can I compress a PDF to exactly 100 KB?
To at most that size, not to exactly it. Our server returns the sharpest version at or under your target, so the file usually comes back a little smaller than the number you chose.
Why is my PDF still above the target?
Because none of the resolutions our server tried, down to Extreme, made a small enough file. That happens with a mostly-text PDF, where there are few pictures to shrink, and with long documents full of photos. Try “Grayscale”, or split the file.
Will my PDF turn black and white to hit the target?
No. Colour is kept unless you tick “Grayscale” yourself; the server never removes it to reach a size.
Is my PDF uploaded?
Yes, to reach a target: the size breakdown and the lossless copy run in your browser, but a target is reached by the deep step on our server. An optional, clearly labeled step uploads the file to a secure server — only when you start it, and only after the page confirms a server is available. The uploaded file is deleted when the job ends, and the result can be downloaded for 60 minutes.
How large can my PDF be?
Up to 100 MB per file.