PDFMonks

Compress PDF
without losing quality

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

Quality here has a definition, not a feeling. Two of the four compression methods never touch a pixel: one subsets fonts to the glyphs the pages draw, one rebuilds the document and drops orphaned objects. Both leave the page identical at any zoom. This page runs those first and tells you when they were enough.

How to compress a PDF without losing quality

  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. Name the size

    Choose a compression level, pick a target below the file's current size from the chips, or type your own smaller number in KB or MB.

  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.

What lossless actually means in a PDF

A PDF carries three kinds of weight. Fonts, which ship with every glyph they were designed with while the page draws a few dozen. Dead structure, meaning orphaned objects and the old revisions a file keeps every time somebody saves it. And images, which are the only part where making the file smaller can make the page worse. Only the third one forces a choice: you reduce the image data, or you keep the pixels and accept the size.

Work on the first two and the rendered page looks identical at any zoom. That is what this target does first. It is not a quality slider set high, it is a different operation that has no quality to set. The font subset removes unused glyphs, the structural rebuild drops orphaned objects, and the output looks identical to the original at any zoom level.

This is why a text document can lose most of its weight without any visible change. The weight is in the fonts and the structure, not in the pixels, and the lossless methods target exactly that.

The two things this page measures to prove quality

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. A refused candidate is not offered for download.

Image resolution is the second. When the lossless methods are enough, no image is re-encoded at all and the original pixels ship unchanged. When they are not, the compress tool says which method won, so you always know whether a pixel was touched. The result names the winning method on the page, and that name is your proof.

Page count is also checked. The output is opened and its pages are counted against the source, so a compression run that dropped pages would be caught and refused before it ever reaches the download button.

When lossless compression is not enough

Sometimes the honest answer is that the file cannot get much smaller without a visible cost. Even documents that barely shrink still get a real result rather than a failure. Font-heavy exports often lose most of their weight without failing the text and page checks; lossless winners touch no pixels, and image winners name the quality on the page.

If you have a hard cap to meet, pick the number instead of the principle. A 1 MB target or the large file page will get you there and tell you exactly what it cost. The tool refuses any candidate below 98% of the source's non-space characters, so even when images are re-encoded, the text stays selectable and correct.

The trade is always between image quality and file size, and the tool tells you exactly where it landed. If the lossless methods reached the target, nothing was touched. If the image method won, the quality it picked is on the page for you to judge.

Real use cases for lossless PDF compression

Text documents with embedded fonts. Font subsetting often brings a text PDF under a 1 MB cap without touching a single pixel, and the output renders as sharp as the original at any zoom.

Saved and re-saved files that carry old revisions and orphaned objects. The structural rebuild drops the dead weight and leaves the rendered page identical at any zoom.

Legal and financial documents where text integrity is non-negotiable. The 98% retention check and the page count check refuse any candidate that lost characters or pages.

Questions about compressing a PDF without losing quality

Can you compress a PDF without losing quality at all?
Yes, when the weight is in fonts and dead structure rather than in images. Subsetting fonts and rebuilding the document change nothing on the rendered page. Whether it is enough depends on the document, and the tool reports which method won.
How much smaller does lossless compression get a file?
It varies enormously. A font heavy text export can lose most of its weight losslessly. A scan cannot, because its weight is pixels.
How do you prove the quality was kept?
Every candidate is re-opened and read back before it ships. Page count is compared, characters are compared, and a candidate below 98% retention is discarded. The result also names the winning method, which tells you whether any image was re-encoded.
Is lossless compression slower?
No, and it is often faster, because the methods that do not touch images finish sooner and stop the race. The read back check is part of every run.
What happens when lossless methods cannot reach the target?
The image method runs as a last resort. It samples pages, picks the quality that fits, and will not go below a fixed floor. The result names the winning method, so you know a pixel was touched and can judge the trade before you download.
Does pdfmonks add a watermark to the compressed file?
No. There is no watermark, no account, and your PDF is never uploaded. The file is processed in your browser and the output is exactly what the engine produced, with nothing added.

The other pdfmonks 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