PDF Compressor
Reduce PDF file size using lossless compression.
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PDF files only
Reduce PDF file size in your browser — no upload
Email attachments have size limits, cloud storage fills up, and large PDFs load slowly on mobile devices. This free PDF compressor reduces file size using lossless structural optimisation — compressing object streams, removing redundant metadata, and cleaning up internal cross-reference tables. All processing runs in your browser with pdf-lib, so your documents never touch a server.
What does lossless PDF compression do?
A PDF file is not just content — it contains internal object tables, metadata fields, embedded font subsetting data, and cross-reference indexes that accumulate over multiple edits and exports. Lossless compression removes this overhead without touching visible content. It is most effective on PDFs saved and re-saved multiple times, PDFs exported from Word or Google Docs, and PDFs with verbose metadata added by the creating application.
How much will my PDF shrink?
Results vary widely. A clean, freshly exported PDF from a modern tool may reduce by 5–20%. A PDF that has been repeatedly edited, annotated, and resaved in different applications can shrink by 30–60%. PDFs that are mostly high-resolution scanned images will see minimal reduction from structural compression alone — for image-heavy PDFs, compress the images before creating the PDF for the best results.
When to use PDF compression
Use this tool before emailing a PDF when the attachment exceeds a recipient's size limit, before uploading to a government portal or job application form that enforces file size caps, when archiving large volumes of PDFs to save storage, before sharing PDFs in messaging apps like WhatsApp that have upload limits, and when uploading PDFs to websites where page load speed matters.
Safe for sensitive documents
Because compression happens entirely in your browser, this tool is suitable for confidential contracts, financial statements, medical reports, and legal documents. Nothing is sent to a third-party server, no account is required, and files are cleared from memory when you close the tab or navigate away.
Frequently asked questions
- How much can this tool reduce my PDF size?
- Results vary significantly by PDF content. PDFs with redundant cross-reference tables, unused embedded objects, or verbose metadata can shrink by 10–40%. Tightly optimised PDFs exported by professional tools like Adobe Acrobat may barely shrink at all. Image-heavy PDFs benefit most — but for those, the biggest gains come from compressing the source images before they are converted to PDF, rather than compressing the PDF afterward.
- Why is my compressed PDF not smaller?
- Many modern PDF generators already apply object stream compression and optimised cross-reference tables. PDFs created by Chrome's print-to-PDF function, Adobe Acrobat, Microsoft Word's PDF export, or Canva are typically well-optimised already. For PDFs containing large images, use the Image Compressor tool first to reduce image file sizes, then convert them to PDF to get meaningful size reduction.
- Does compression affect PDF quality?
- The compression performed by this tool is structurally lossless — it removes redundant data, unused objects, and unnecessary metadata from the PDF container without touching the actual image, font, or text content. The visual output is pixel-identical to the original. No image resampling or quality reduction is applied during this compression process.