Compress PDF online

Reduce a PDF's file size without uploading it to our server.

🔒 File stays in your browser

Choose a PDF file

Select the PDF you want to make smaller.

Select PDF

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Compression level

LightSafest optimisation. Preserves maximum compatibility. RecommendedGood general-purpose optimisation for sharing and email. StrongMore aggressive stream optimisation. Results vary by PDF.

Worth knowing: browser-side lossless optimisation cannot always make a PDF smaller. PDFs containing already-compressed photographs may need image downsampling for a major reduction; we'll add that as the next compression upgrade rather than silently reducing document quality.

About this tool

Reduce the size of a PDF for easier sharing, email or storage. Choose a compression level and the tool will optimise the document directly in your browser.

Compression results depend on the contents of the PDF. Files containing images that are already heavily compressed may show a smaller reduction.

Practical guide

What does Compress PDF do?

Reduce a PDF's file size to make it easier to email, upload or store.

When is it useful?

Useful when a website or email service has a file-size limit, or when a large PDF is slow to share.

What should I know before downloading?

Compression can affect image quality. Check the downloaded copy before deleting your original.

Why might the compressed file look different?
Reducing file size can require images to be recompressed. Always check the downloaded PDF if image detail is important.

Are my files uploaded?

This tool is designed to process the document in your browser. PDFOnline.co.uk does not intentionally receive or store the PDF you select for this tool.