Compress PDF

Reduce your PDF's file size by choosing a compression level. Runs entirely in your browser.

Compress a PDF

Upload a PDF, choose a compression level, then compress and download the result.

Drag & drop a PDF here, or click to browse
Works best on scanned or image-heavy PDFs.

    Result

    Original size
    0 KB
    Compressed size
    0 KB
    Reduction
    0%
    Your PDF is processed locally in this browser tab using pdf.js and pdf-lib. It is never uploaded to Calcooo or any server.

    How to use this tool

    1. Drag and drop your PDF into the box above, or click to browse and select it.
    2. Choose a compression level — Low, Medium or High.
    3. Press Compress PDF and wait while each page is processed.
    4. Click Download compressed.pdf to save the result to your device.

    FAQ

    Frequently asked questions

    Is my PDF uploaded anywhere when I compress it?

    No. Compression happens entirely inside your browser using JavaScript — pdf.js renders each page and pdf-lib rebuilds the file. Your PDF never leaves your device.

    How does the compression actually work?

    Each page is re-rendered as a JPEG image at your chosen quality level, then reassembled into a new PDF. This shrinks image-heavy and scanned PDFs the most.

    Will the text in my PDF stay selectable?

    No. Because pages are rasterized to images, text becomes part of the image and is no longer selectable or searchable. Use this tool when file size matters more than keeping text selectable. For PDFs that are mostly text, the size reduction may be modest, or the file could even end up slightly larger — that's expected and shown honestly in the result.

    Which compression level should I pick?

    High compression gives the smallest file but lower image quality. Low compression keeps the largest file size with the best quality. Medium is a good default for most PDFs.