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PDF Compressor

Try to make a PDF smaller using in-browser optimisation. Results depend on what is inside the file, and the tool tells you plainly when no meaningful reduction is possible.

1. Choose a PDF

Why results vary

A PDF is a container. How much it can shrink depends on what is inside, and no tool can promise a percentage in advance. This tool shows you the real before and after sizes and only offers a download when the result is actually smaller.

  • Lossless optimise keeps every page, font and image exactly as it is and only tidies the file structure. Files from modern exporters, text-only documents and PDFs with already-compressed JPEGs often shrink by little or not at all.
  • Strong mode converts each page to a JPEG picture. It can make scans and photo-heavy PDFs much smaller, but it removes selectable text and flattens vector graphics. A text-only PDF can even grow, because a picture of text is bigger than the text itself.
  • Resolution is estimated as 72 points per inch times the render scale. Real print sharpness also depends on the page size and how you print it.

How to use the PDF Compressor

  1. Drop a PDF onto the upload area, or click it to browse. The file must be a real PDF and no larger than 100 MB. Its size and page count appear straight away.
  2. Pick a method. Lossless optimise is the default: it keeps text selectable and quality identical. Strong (rasterise pages) turns every page into a JPEG picture, so read the warning and tick the box to confirm.
  3. In Strong mode choose a preset: Balanced, Smaller or Smallest. Each one shows the resolution it assumes (in DPI) and the JPEG quality it uses.
  4. Press Compress PDF. A progress bar shows the current page, and you can press Cancel at any time. Your original file is never changed.
  5. Read the result. You see the original size, the new size and the real percentage change. If it is smaller, compare the before and after previews, then download it. If it is not meaningfully smaller, the tool says so instead of calling it a win.

Two ways to shrink a PDF, and why neither is magic

A PDF is a container of objects: page descriptions, fonts, and images. Lossless optimise re-saves those objects with a more compact structure (object streams) and can optionally remove metadata. It never touches the pixels of an image or the text on a page, which is why quality and text selection are unchanged. The catch is that if the file was already saved compactly, there is almost nothing left to remove.

Strong mode takes a different route. Each page is drawn onto a canvas at a chosen resolution, encoded as a JPEG, and a new PDF is built from those pictures. For scans and photo-heavy documents this can make a big difference. The price is real: text becomes part of the picture, so it can no longer be selected or searched, links and form fields stop working, and vector graphics are flattened. A page that was mostly text can even get bigger.

Because the outcome depends entirely on what is inside your file, the tool never promises a percentage. It compares the real byte counts and treats a result as meaningful only when it is at least 3% smaller. A difference of under 1% or under 1 KB is reported as no real change, and a larger result is never offered as a compressed download.

Percent saved = (original bytes - result bytes) / original bytes x 100
Same size: |difference| < 1% of the original, or < 1 KB (1,024 bytes)
Meaningful reduction: at least 3% smaller
Effective DPI = 72 x render scale (a PDF point is 1/72 inch)
Canvas pixels = (page width pt x scale) x (page height pt x scale), capped at 16,000,000 per page

Assumptions and limits

  • The tool cannot predict the final size. It only reports the real result after compressing.
  • Lossless optimise does not recompress images, subset fonts or remove duplicate resources, so it cannot match the savings of a desktop PDF optimiser on image-heavy files.
  • Strong mode flattens everything to pictures: no selectable text, no working links or form fields, and no accessibility tags.
  • DPI figures assume one PDF point equals 1/72 inch. Real print sharpness depends on the page size and how you print.
  • Encrypted or badly damaged PDFs cannot be processed. A file that opens in one viewer may still be rejected here.
  • Very large pages are rendered at a lower resolution to stay within the browser's canvas memory limits, and the result tells you when that happened.
  • Cancel stops Strong mode between pages. Lossless optimise cannot be interrupted part-way, so Cancel takes effect when it finishes.

Practical examples

Lossless optimise on a text-only file

We generated a 40-page, US Letter, text-only PDF and saved it without object streams. It was 64,370 bytes (62.86 KB). After lossless optimise it was 31,200 bytes (30.47 KB): 33,170 bytes saved, or 51.53% smaller. Running the optimised file through the tool a second time gave exactly 31,200 bytes again, so there was no further saving. A file that was already saved this compactly has nothing left to gain, which is why results vary so much from one PDF to the next. The exact figures come from our generated test file and will differ for yours.

Reading the three possible verdicts

2,000,000 bytes (1.91 MB) down to 1,500,000 bytes (1.43 MB) is 25% smaller, a meaningful reduction. 200,000 bytes down to 197,000 bytes is only 1.5% (3,000 bytes) smaller: still a download option, but the tool warns that no meaningful reduction was possible. 3,000,000 bytes growing to 3,300,000 bytes is 10% larger, so no download is offered and the original is the better file.

What each Strong preset renders

A US Letter page is 612 x 792 points. Balanced draws it at scale 1.5, which is 918 x 1188 pixels (108 DPI) at JPEG quality 70%. Smaller uses scale 1.25, which is 765 x 990 pixels (90 DPI) at quality 55%. Smallest uses scale 1, which is 612 x 792 pixels (72 DPI) at quality 40%. Lower resolution and quality mean smaller pictures, but also softer text.

Frequently asked questions

Why did my PDF barely shrink, or not shrink at all?

Most of a PDF's weight is usually its images and embedded fonts. If the images are already compressed JPEGs and the file was saved by a good exporter, lossless optimise has nothing left to remove. Strong mode may help for scans, but it removes selectable text.

Will I still be able to select and search the text?

With Lossless optimise, yes: text, fonts and images are kept exactly as they were. With Strong mode, no: every page becomes a picture, so text cannot be selected, searched or copied, and links and form fields stop working.

Why does the tool say the result is larger than the original?

Re-saving or rasterising can add overhead, and a JPEG picture of a text page can be bigger than the text itself. When that happens the tool tells you and does not offer the file as compressed. Your original is unchanged.

Is my PDF uploaded anywhere?

No. The file is read and processed by your browser on your own device, and nothing is sent to a server. Close the tab or press Reset and the working copies are discarded.

Can it open a password-protected PDF?

No. Encrypted files are rejected with a clear message. Remove the protection in the program that created the file (you will need the password), then try again.

Is there a size or page limit?

Files can be up to 100 MB. Strong mode renders every page in your browser's memory, so it is limited to 300 pages, and any single page that would need more than 16 million pixels is rendered at a lower resolution.

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