How It Works
Frequently Asked Questions
Everything you need to know about compressing PDFs
Absolutely safe. All compression happens 100% inside your browser using JavaScript — PDF.js renders each page, and pdf-lib rebuilds the output. Your file never leaves your device and is never transmitted to any server. No data is stored, logged, or shared. Your documents remain completely private.
Results vary significantly depending on the PDF content. Image-heavy PDFs (scanned documents, brochures, photos) can shrink by 50–80% on Max Compression. Text-only PDFs (reports, contracts, forms with minimal graphics) may only reduce by 10–30%, because the tool re-renders pages as JPEG images — text that is already small in the original doesn't compress much further.
This is expected behavior for this browser-based tool. The compression works by rendering each page to a canvas and saving it as a JPEG image. The output is a collection of page images wrapped in a PDF container — text is part of the image, so it cannot be selected, copied, or searched. If you need a searchable compressed PDF, use a dedicated desktop tool like Adobe Acrobat or Smallpdf (which performs server-side compression).
The three levels control the rendering scale and JPEG quality used when converting each page:
Max Compression — scale 1×, JPEG quality 40%. Smallest possible file. Noticeable visual quality loss on images and diagrams. Best for sharing or archiving where file size matters most.
Balanced — scale 1.5×, JPEG quality 65%. Good middle ground. Acceptable quality for most everyday documents.
High Quality — scale 2×, JPEG quality 85%. Best visual fidelity. Larger output than the other modes, but still typically smaller than a fully uncompressed PDF with embedded high-res images.
This can happen with text-only or vector PDFs. If your original PDF contains lightweight vector graphics, mathematical symbols, or plain text with no embedded images, the original file is already highly efficient. Re-rendering pages as JPEG images (which have fixed overhead per page) can actually increase the size. In this case, try the High Quality mode, or use a server-side tool that can apply smarter PDF optimization without converting to images.
No. Password-protected (encrypted) PDFs cannot be read by the browser without the decryption key. You will see an error if you attempt to upload one. To compress a protected PDF, first remove the password using Adobe Acrobat, your PDF viewer's "Print to PDF" feature, or an online unlock tool — then upload the unprotected file here.
On screen, the result looks very close to the original at normal zoom levels, especially with Balanced or High Quality modes. At high zoom (200%+), JPEG compression artifacts may become visible on images. For print, High Quality mode produces the sharpest output. Max Compression is not recommended for high-fidelity print jobs — use Balanced or High Quality instead.
The upload limit is 50 MB. Since all processing happens in your browser, very large or heavily paged PDFs (100+ pages) can be slow and may consume significant RAM. If compression stalls or the page becomes unresponsive: (1) Close other browser tabs to free memory. (2) Split the PDF into smaller chunks before compressing. (3) Use a desktop machine rather than a phone for large files.
Yes. The tool works on any modern browser — Chrome, Firefox, Safari, Edge — on both desktop and mobile. On mobile, tap the upload area to select a PDF from your files or cloud storage. Note that large PDFs may compress more slowly on mobile due to lower RAM and CPU performance. For best results with large files, use a desktop browser.
Yes — completely free with no registration, no login, no account required, and no watermark added to the output. There are no daily usage limits. Compress as many PDFs as you need.