How to Compress a PDF Online for Free

A smaller PDF file is easier to email, upload, and share — especially when file size limits get in the way. Our free PDF compressor strips hidden bloat like metadata and page thumbnails, and, if you choose a higher compression level, re-encodes embedded photos at a lower quality to shrink the file further — directly in your browser, instantly and privately, with no sign-up required.

Step-by-Step: How to Use This Tool

• Click "Select PDF File" or drag and drop your PDF into the upload area above
• Choose a compression level: Low, Recommended, or High
• Click "Compress PDF" — compression happens instantly in your browser
• Compare the original and compressed file sizes shown after compression
• Your compressed .pdf file downloads automatically — open it in any PDF viewer

Which Compression Level Should I Choose?

• Low — keeps embedded photos close to their original quality. Best when the PDF will be printed or viewed closely.
• Recommended — a balanced setting that noticeably shrinks file size while keeping photos looking good on screen.
• High — the smallest file size. Photos are compressed more aggressively and downscaled if very large, so choose this when file size matters more than image sharpness (e.g. email attachments).

Will Compression Affect Quality?

Text, tables, and vector graphics are never touched at any compression level — they stay exactly as sharp as the original. Only embedded photos are re-encoded, and the amount of quality loss depends on the level you choose: minimal at Low, more noticeable at High.

Is This Tool Safe for Confidential PDFs?

Yes — completely safe. Unlike cloud-based compressors that require uploading your file to a remote server, this tool uses the pdf-lib library to process your PDF entirely within your browser. Your file never leaves your device, making it safe for confidential documents including contracts and financial reports.

Compress PDF — Common Uses

• Shrink a PDF to fit under an email attachment size limit
• Reduce file size before uploading to a website or portal
• Prepare a lighter PDF for faster sharing over messaging apps
• Free up storage space when archiving large document collections
• Speed up PDF loading on slow internet connections

Compressing PDFs Made From Images

If your PDF was created from scanned pages or photos — a common case for PDFs built with an image converter or a pdf to image converter workflow — most of the file size lives in those embedded images, so this tool can typically save the most space here. If you're starting from individual photos instead of a finished PDF, our free image converter tools let you convert to JPG, PNG, or WebP and resize before you ever combine them into a PDF, which often produces an even smaller final file than compressing after the fact.