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Compress PDF

Reduce your PDF file size in seconds. Choose your compression level and download a smaller file instantly.

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Why compress a PDF?

PDF files can grow surprisingly large — a 10-page report with photographs can easily reach 20–30MB, a scanned document may be 5–15MB per page, and slide-heavy presentations can reach 100MB or more. Large PDFs cause problems: email servers reject attachments over 10–25MB, upload forms have file size limits, and cloud storage fills up quickly. Compressing a PDF reduces its size while keeping the content readable and shareable.

This tool compresses PDFs by re-rendering each page onto an HTML canvas at a lower resolution and re-encoding it as a JPEG image, then reassembling the pages into a new PDF using pdf-lib. The result is a smaller file where image quality is reduced just enough to achieve meaningful size savings. All processing happens inside your browser — no file is ever uploaded to a server.

How to compress a PDF — step by step

  1. Upload your PDF by clicking the area above or dragging it onto the page.
  2. Choose your compression level: Strong (smallest file, most compression), Balanced (recommended — good quality at much smaller size), or Light (minimal compression, best preserved quality).
  3. Click Compress PDF. Each page is rendered and re-encoded. A progress bar tracks the process.
  4. The results screen shows your original file size, the new compressed size, and the percentage reduction. Click Download Compressed PDF to save the file.

If the size reduction is less than 10%, a warning appears. This typically means the PDF is already efficient (text-heavy or previously compressed).

Understanding the three compression levels

  • Strong — 72 DPI, 55% JPEG quality: Maximum size reduction. Best for PDFs that will only be viewed on screen and where file size is the priority — email attachments with strict size limits, upload forms, mobile sharing. Text may appear slightly soft at this level.
  • Balanced — 96 DPI, 72% JPEG quality: The recommended choice for most use cases. Achieves 40–70% size reduction on image-heavy PDFs while keeping text legible and photos looking good. Suitable for professional sharing, web uploading, and printing at normal sizes.
  • Light — 120 DPI, 88% JPEG quality: Minimal compression. Good when you need to reduce size slightly while preserving near-original visual quality. Useful for documents with fine print, detailed diagrams, or professional photography where quality matters more than size.

Why PDFs get large — and what compression actually does

PDFs bloat in size for several common reasons: embedded high-resolution photos (a 12MP phone camera creates 3–5MB images), scanned pages saved at 300+ DPI, embedded fonts that duplicate character data, complex vector graphics, and metadata embedded by design software.

Browser-based compression works by converting each page to a bitmap image (via HTML canvas), then applying JPEG compression. This is very effective on image-heavy PDFs and scanned documents, because it replaces large embedded images with smaller re-encoded ones. However, it is less effective on text-only PDFs because the text was already stored efficiently as vector data — converting to JPEG actually replaces efficient vector text with a larger pixel representation.

For purely text-based PDFs, a specialized server-side tool that strips metadata and rebuilds the PDF structure will achieve better results. This browser-based tool is most effective on documents that contain photographs, illustrations, or scanned pages.

Frequently Asked Questions

Upload your PDF, choose a compression level (Balanced is a good default), and click Compress. The tool re-renders each page at a lower resolution and JPEG quality, then rebuilds the PDF. The size reduction is shown before you download.
Yes, to some degree — pages are re-rendered as JPEG images, so there is lossy compression. At Balanced level, the quality reduction is barely noticeable for most documents. At Strong level, very fine text or detailed diagrams may appear slightly softer. Use Light if you need near-original quality.
Text-only PDFs may compress very little because text data is already stored compactly as vector characters. This tool achieves the best results on image-heavy PDFs, scanned documents, and slide decks with photos. A warning appears if the reduction is less than 10%.
Start with Balanced — it works well for most documents. If the result is still too large, try Strong. If the quality at Balanced looks too degraded for your use case (fine print, detailed diagrams), use Light.
No. The entire compression process happens inside your browser. The PDF is rendered using PDF.js and rebuilt using pdf-lib — both JavaScript libraries that run locally. Nothing leaves your device.
No. Password-protected PDFs cannot be rendered or processed. Remove the password in your PDF viewer before uploading the file for compression.

Related tools

  • Split PDF — Remove unwanted pages before compressing to reduce size further.
  • Merge PDF — Combine smaller PDFs into one document after compression.
  • PDF to JPG — Extract individual pages as images if the PDF format is not required.