How to Compress a PDF Online

A PDF file can contain text, vector graphics, embedded fonts, and raster images. Most of the file size in a typical PDF comes from the raster images — scanned pages, photos, screenshots — not from the text itself. Compressing a PDF works by re-encoding these embedded images at a lower resolution and a higher JPEG compression level, which dramatically shrinks the file with only a small visible quality loss.

Text and vector content (line art, charts, solid shapes) are not re-encoded during compression, so they remain crisp and selectable. This is why a 30 MB scanned document can often be compressed to under 3 MB without any visible degradation of the printed text, while a 1 MB text-only contract might not shrink at all — there is simply nothing to compress.

Modern PDF compressors run inside the browser using JavaScript and WebAssembly. This means your file never leaves your device, which is a major privacy advantage over server-side tools that upload your document to a remote server for processing.

Email providers like Gmail, Outlook, and Yahoo typically limit attachments to 25 MB. If your PDF is larger than that, compression is usually the fastest fix. Many web forms — grant applications, job portals, government sites — also impose file size limits, often between 2 MB and 10 MB. Compression lets you fit under these limits without removing content.

Compression is also useful for archival. A folder of 200 scanned receipts at 8 MB each adds up to 1.6 GB; compressed at the recommended quality setting, the same folder may shrink to under 300 MB, with no practical loss of readability.

On the other hand, if your PDF is destined for high-quality printing (offset press, fine art prints, legal exhibits), aggressive compression may degrade the output. In those cases, use Light compression or skip it entirely and ship the file via a file-sharing service instead.

Open the Compress PDF tool in any modern browser — Chrome, Firefox, Safari, or Edge on desktop or mobile. You do not need to install anything or create an account.

Drag your PDF file into the upload area, or click the area to browse and select the file. The tool reads the file directly from your device's storage; nothing is uploaded.

Choose a compression level. Recommended works for most use cases — it typically reduces scanned PDFs by 70–90% with no visible quality loss. Strong shrinks further but may slightly soften images. Light is best when you want a small reduction with maximum fidelity.

Click the Compress button. The tool scans the PDF, re-encodes embedded images, and produces a new PDF. For a typical 10 MB scanned document, this takes a few seconds.

Compare the original and compressed sizes shown side by side. If the result fits your target size, click Download to save the new PDF. If it is still too large, try the next stronger compression level.

Light compression re-encodes images at roughly 80% of the original quality. It usually yields a 20–40% file size reduction. Use it for documents that will be printed or archived at high quality.

Recommended (medium) compression drops image quality to about 65% and reduces DPI to 150. This is the sweet spot for email attachments and web uploads, typically shrinking files by 60–80% with no visible degradation on screen.

Strong compression re-encodes at 40% quality and 100 DPI. File sizes often shrink by 85–95%, making this ideal for thumbnails, preview files, or documents where small size matters more than crispness. Photographic content may show visible artifacts at this level.

If your PDF contains sensitive information — tax returns, medical records, legal documents, signed contracts — server-based compression tools pose a real risk. Even when a service promises to delete your file after a short time, you have no way to verify it, and the file is exposed during upload and processing.

Browser-based compression eliminates this risk entirely. The PDF is read into your browser's memory, processed locally, and the only thing that touches the network is the page itself (HTML, CSS, JavaScript). When you close the tab, the file is gone.

If you must use a server-based tool for some reason, look for one that explicitly supports end-to-end encryption, posts a clear retention policy, and has been independently audited. Even then, prefer local tools for anything confidential.