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PDF Compressor

Make a PDF smaller in your browser, and see exactly how much it saved. If it can't be made smaller, you're told so.
Runs in your browser. Nothing is uploaded.

Your PDF is compressed locally in this browser. Nothing is uploaded.

How to use the PDF Compressor

  1. Choose a PDF. It is read only in your browser.
  2. Pick a level (Light, Balanced or Strong) and a method. Keep text is the default.
  3. Select Compress PDF. Compare the original and new size, then download the smaller file.

Examples

  • A report full of photos. Large photos are re-encoded at a lower resolution, often saving a lot while text stays sharp and searchable.
  • A scanned document. Convert pages to images at a lower resolution for the biggest saving; the text wasn't selectable anyway.
  • A text-only PDF. There is usually little to remove. The tool says so instead of giving you a file that isn't smaller.

How the compression works

Keep text rewrites the PDF with pdf-lib using compressed object streams and removes objects that nothing in the document refers to (often left behind by earlier edits). Embedded images stored as JPEG, or as Flate-compressed RGB or grey pixels without a predictor, are decoded by your browser, scaled down to at most 2,400, 1,600 or 1,100 pixels on the long side, and saved as JPEG at the chosen quality. An image is only replaced when the new version is at least 10% smaller. Text, vector graphics, fonts, links and form fields aren't changed.

Images that can't be safely re-encoded are left exactly as they are: CMYK and other colour spaces, masks, images with special decoding rules, and small images. Fonts are not subset or removed.

Convert pages to images renders each page with PDF.js at 150, 120 or 90 DPI and builds a new PDF from those images. It usually saves the most for scans, but the text can't be selected, searched or read aloud any more, and links, bookmarks, forms and annotations are removed.

Important: re-saving a PDF can invalidate certificate-based digital signatures already in the original file. Keep the original if its signatures need to stay valid.

Honest results

Every result is compared with the original. If the new file isn't smaller, no download is offered and the size of the best attempt is shown. How much a PDF shrinks depends on what's inside it: a text-only PDF may shrink very little, a photo-heavy one a lot.

Frequently asked questions

Why didn't my PDF get smaller?

It was probably already compressed well, or mostly made of text and fonts, which this tool doesn't change. Try Strong, or Convert pages to images if you don't need selectable text.

Will the quality change?

With Keep text, only photos change, and Light keeps them closest to the original. Text and drawings stay sharp. Converting pages to images softens everything slightly.

Is my PDF uploaded?

No. Compression runs in your browser with pdf-lib, PDF.js and the browser's own image encoder. Nothing is sent to a server.

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