A PDF compressor reduces the file size of a PDF so it is easier to email, upload, or store. The compressor below works entirely in your browser by redrawing each page as an image at a quality level you choose and rebuilding the PDF from those images, which shrinks scanned and image-heavy files the most.
What PDF Compression Is
PDF compression is the process of making a PDF take up fewer bytes while keeping it readable. A PDF can be large for several reasons: high-resolution scanned pages, embedded photos, or images saved at a higher quality than the document needs. Compression cuts that excess. Some methods keep the text layer intact and only shrink the images. This tool takes a different, more aggressive route: it turns each whole page into a single image, which produces a smaller and more predictable result for documents that are mostly pictures or scans.
How to Use This PDF Compressor
- Choose a PDF file from your device. It stays on your device and is never uploaded.
- Pick a quality level. High keeps more detail and a larger file; Low produces the smallest file.
- Pick a render scale. 1x is the smallest, while 1.5x or 2x keeps text and lines sharper.
- Press Compress PDF and wait while each page is redrawn and rebuilt.
- Check the original size against the compressed size, then use the download link to save the new file.
How This Tool Compresses
The tool loads your PDF with pdf.js, draws each page onto a canvas at the render scale you chose, and exports that canvas as a JPEG at your chosen quality. It then embeds each JPEG into a fresh PDF built with pdf-lib, one image per page. The result is a document made entirely of pictures of your original pages. This is why the size drops on scanned and image-heavy files: a single JPEG of a page is often far smaller than the page’s original content.
When It Helps Most
This approach shrinks some PDFs a lot and others not at all. The deciding factor is what the PDF is made of.
| PDF type | Result with this tool |
|---|---|
| Scanned documents | Large reduction. Scans are already images, so re-encoding them at a chosen quality drops size. |
| Image-heavy PDFs | Large reduction. Photos and graphics compress well as JPEGs. |
| Text-only PDFs | Often grows or barely shrinks. Crisp text is small as text but heavy as an image, and you lose selectable text. |
| Mixed text and images | Varies. Test it, compare the sizes, and decide if losing selectable text is acceptable. |
Quality Versus Size
Two controls decide the outcome. Quality sets how much detail each JPEG keeps: High at 0.8 holds more detail and produces a larger file, while Low at 0.4 discards more and produces a smaller file. Render scale sets how many pixels each page is drawn at: 1x is the smallest output, while 2x keeps lines and small text sharper at the cost of size. Start with Medium quality and 1.5x scale, compare the sizes the tool reports, and adjust. If the file is still too large, lower the quality before lowering the scale, since dropping quality usually saves size with less visible damage to readability.
Everything Stays in Your Browser
Your PDF is read, rendered, and rebuilt on your own device. Nothing is uploaded to a server, logged, or stored anywhere, so the file never leaves your computer. That makes the tool safe for documents you would not want to send to an online service, such as contracts, statements, or identity scans. You can confirm this by disconnecting from the internet after the page loads and watching the compressor still work.
When to Use It and When Not To
Use this tool when the file is a scan or is full of images and you need it smaller for an email limit, an upload form, or storage. Do not use it for a text PDF you need to keep selectable, searchable, or accessible, because flattening the pages destroys the text layer. For those files, look for a compressor that shrinks only the embedded images and leaves the text intact, or send the document as is if its size is already reasonable.
Last Thoughts on Compressing PDFs
Most oversized PDFs are oversized because of their images, and that is exactly the case this tool handles well. By redrawing each page as a JPEG and rebuilding the document, it trades the selectable text layer for a smaller file, which is the right trade for scans and photo-heavy documents and the wrong trade for clean text you need to copy.
Compress your next scanned PDF above, then compare the before and after sizes. When you need to combine or break up files instead of shrinking them, try our PDF merge and PDF split tools, shrink a single picture with the image compressor, and browse the rest of our free online tools.
Key Takeaways:
- This tool compresses a PDF by rasterizing each page to a JPEG and rebuilding the document from those images.
- It shrinks scanned and image-heavy PDFs the most, and often does little for clean text PDFs.
- The tradeoff is real: the text becomes a flat image, so it is no longer selectable, searchable, or readable by a screen reader.
- Quality and render scale control the result; lower quality before lower scale when you need a smaller file.
- The whole process runs in your browser, so the file is never uploaded.
- Use it for scans and images; avoid it for text PDFs you need to keep selectable.
Frequently Asked Questions (FAQs)
Does this PDF compressor upload my file?
No. The PDF is read, rendered, and rebuilt entirely inside your browser using pdf.js and pdf-lib. The file is never sent to a server, logged, or stored. You can disconnect from the internet after the page loads and the tool will still compress your PDF.
Why is the text in my compressed PDF no longer selectable?
This tool works by turning each page into an image and rebuilding the PDF from those images. That image has no text layer, so the words are now part of a picture. They cannot be selected, copied, searched, or read by a screen reader. If you need selectable text, use a method that compresses only the images and keeps the text intact.
Which PDFs does this compress the most?
Scanned documents and image-heavy PDFs shrink the most, because their pages are already pictures and re-encoding them as JPEGs at a chosen quality cuts the size. Clean text-only PDFs often barely shrink or even grow, since sharp text is small as text but heavy as an image.
What should I set quality and render scale to?
Start with Medium quality and 1.5x render scale, then compare the sizes the tool reports. If the file is still too large, lower the quality first, because dropping quality usually saves more size with less visible loss than dropping the render scale.
My file did not get smaller. Why?
That usually means the PDF was already mostly text or was already well compressed. Turning crisp text into an image can produce a file the same size or larger. This tool is built for scans and image-heavy documents, so a text PDF may show little or no reduction.
Can it compress a password-protected PDF?
No. Encrypted or password-protected PDFs cannot be opened and rebuilt by this tool, and damaged files may also fail. Remove the protection first, then compress the unlocked copy.
