Compress PDF

Drop your PDF into the box below and you get it back smaller, without it going anywhere near a server. It is the same file, just lighter to email.

And if you have tried one of these before and got back a file that was barely any smaller, do not worry, you did nothing wrong and you are not alone. There is a real reason for it, and this page will tell you which reason applies to your file instead of just showing you a percentage.

Nothing is uploaded. The work happens inside your own browser, and the page keeps working with the network switched off.

There are two completely different ways to compress a PDF

When you look for a way to compress PDF files, every tool you find does both of them at once, adds up the saving, and calls the total compression. That hides the only thing you actually need to know, which is whether your document changed.

One: throwing away leftovers, which costs you nothing at all

This one surprises people, and it is the more interesting half.

When a program saves a PDF it usually adds to the end of the file rather than rewriting it. That is deliberate, because it is fast and it means a crash halfway through does not destroy your work.

The effect, though, is that an edited PDF is like a notebook where nothing is ever rubbed out. Every earlier version of every page you touched is still in there, further back, with a note at the front saying which version counts. Delete a page, swap a photograph, change a heading, and the old one is still sitting in the file taking up room.

Rebuilding the document, keeping only what it still points at, leaves all of that behind. Nothing you can see changes. The text is identical, the pictures are byte for byte the same ones, and the file is smaller.

On a file that has been round a few people this alone can be a third of the size. On a file that was written once and never edited it will be almost nothing, and the page says so rather than pretending.

Two: redrawing the photographs, which does change them

In anything with photographs or scans in it, the pictures are almost the whole file. Making them smaller means throwing detail away. There is no way round that, and any tool suggesting otherwise is not being straight with you.

So it is a choice on this page rather than something that happens to you. Pick the quality, or turn it off entirely and take the first kind of saving on its own.

That option matters more than it sounds. If you are emailing a signed contract, you want the file smaller and every pixel of the signature exactly as it was. Every other compressor makes that impossible by doing both jobs at once.

What it will not touch, and why that is the right way round

Some pictures are left exactly as they are, and it tells you how many and for what reason. Skipping one costs you a few kilobytes. Ruining one costs you your document.

• Print colour images. Anything in CMYK, which is what a design program puts in a file destined for a printer. Browsers disagree about how to read those and some come back inverted, so they are not touched.
• Scanned faxes and black and white scans. Those already use a compression built for exactly that job, and redrawing them as photographs would make them bigger and worse.
• Logos, stencils and palette images. Flat colour with hard edges is the one thing photograph compression is worst at. It would smear the edges and grow the file.
• Anything that came out bigger. Redrawing an already well squeezed photograph often produces a larger one. When that happens the original is kept.

And if the whole file comes out no smaller than it started, you are told that plainly and told to keep the original, rather than being handed something 2 percent smaller with a tick next to it.

Why your PDF is big in the first place

It is worth knowing which of these you have, because it decides what is even possible.

• Scanned pages. Every page is a photograph of paper. A 20 page scan can easily be 40 MB. This is where the biggest savings are.
• Photographs dropped in at full camera size. A phone photo is often 4000 pixels wide and printed at 500. Shrinking it loses nothing you can see on the page.
• An edited document with a long history. All the leftovers described above, and the tidy up handles it without changing anything.
• Embedded fonts. A few hundred kilobytes each, and they cannot safely be trimmed without risking characters that stop displaying. This page leaves them alone.

If your file is mostly text with a couple of embedded fonts, there is genuinely almost nothing to take out. No tool anywhere will do better, whatever it claims on its front page.

Frequently asked questions

Is my file uploaded?

No, and you can check rather than believing me. Press F12, open the Network tab, compress a file, and watch nothing go out. Or turn your wifi off and do it anyway.

This matters here more than on most pages, because the files people want to shrink are the ones they are about to email to somebody: contracts, invoices, medical letters, scans of documents with their address on.

Will the text still be selectable?

Yes. Text is never turned into a picture here, whatever setting you choose. Anything you could select and search before, you still can.

Some compressors do flatten pages into images to hit a number. That destroys searching, copying and screen readers, and it is not done here.

Do bookmarks and form fields survive?

Yes. The bookmarks, the page numbering, the form definition and the tagging that screen readers rely on are all carried across, because they are still part of the document. Only what nothing points at is dropped.

It only saved a few percent. Did it work?

It worked. Your file simply did not have much spare in it, and the page will have told you which of the two savings it managed and which it could not.

If you need it much smaller than that, the honest answers are to remove pages you do not need, or to accept a lower picture quality. There is no clever setting that shrinks a text document.

And if what you are really doing is joining several files together, the PDF merger here lets you pick which pages from each one go in. Leaving out the pages you do not need beats any amount of compressing.

Is there a file size limit?

No account and no allowance, because there is no server paying for any of it. The only limit is your own computer’s memory, so a very large scan may be slow on an old phone and is fine on a laptop.

If you have any issues, you can ask me via comment, and I will love to help you out.