Free online tool

PDF Compressor

Compress image-heavy PDF files in your browser by rendering pages at a lower quality and rebuilding the PDF. This tool is useful when a PDF is too large to email or upload.

What is a PDF Compressor?

A PDF compressor is useful when a document is too large to email, upload or store efficiently. Compression usually works by reducing the resolution or quality of image-heavy pages, so the best setting depends on whether readability or the smallest possible file matters more. Always check important pages after compression.

What this tool does

Compress image-heavy PDF files in your browser by rendering pages at a lower quality and rebuilding the PDF. This tool is useful when a PDF is too large to email or upload.

How to use PDF Compressor

1. Select the PDF file you want to shrink using the file picker.
2. Drag the quality slider to balance file size against how sharp the pages look.
3. Click Compress PDF, then compare a few pages of the result against the original before relying on it.

Privacy and file handling

PDF compression runs in your browser rather than on a remote server. The file stays on your device throughout the process, so treat sensitive documents such as contracts, ID scans or medical records with the same care you would use for any file you open locally.

Limitations

• Compression mainly reduces the size of embedded images, so a text-only PDF may shrink very little.
• Pushing the quality slider too low can make small text or fine print hard to read.
• Compressing an already-compressed PDF repeatedly can degrade image quality without much further size reduction.

Why PDF files become large

A PDF containing mostly text can be surprisingly small, while a PDF made from high-resolution photographs can be many times larger. Scanned documents are a common cause because each page may contain a full image rather than selectable text. Compression works by reducing the amount of data needed to represent those images. The best result is therefore a balance: small enough to upload or email, but clear enough that text and diagrams remain readable.

Choose quality based on the job

A document being submitted to a portal may need to stay sharp enough for reviewers to read small text. A PDF being sent as a quick reference may tolerate stronger compression. Start with moderate compression and inspect the result. If the text is still clear, you may not need to compress further. If a page contains photographs, charts or fine print, an aggressive setting can make the loss of detail much more noticeable.

Always compare the original and compressed file

File size alone is not a quality test. Open the compressed PDF and compare several representative pages with the original. Check small text, signatures, diagrams and any page that contains a detailed image. If the output is not acceptable, return to the original and use a lighter setting. Keeping the original file also gives you a safe fallback if the compressed copy is later found to be too soft or damaged.

Privacy and document handling

Compression can be useful for everyday documents, but sensitive material deserves extra care. If a tool uses browser processing, the file may be handled locally by the page, yet third-party libraries, extensions or other browser components can still affect the environment. Do not treat a convenience tool as a substitute for an organisation's approved document-processing workflow when the material is confidential or regulated.

Scanned documents need special care

A scan can look readable at full size and become difficult to read after strong compression. Pay particular attention to small printed text, signatures, stamps and screenshots. If the PDF is being submitted to a government, university or financial service, follow its file-size and readability requirements rather than choosing the smallest possible file.

Do not compress repeatedly

Repeatedly compressing an already compressed document can reduce image quality without giving a useful reduction in size. Keep the original as your master copy and create a new compressed version when you need to meet a particular upload limit. This also makes it easier to return to a higher-quality copy later.

Upload limits are not the only consideration

If a website accepts a 10 MB file, that does not mean you should always compress a 9.9 MB document. A smaller file can upload faster and be easier to store, but excessive compression can make a document harder to use. Aim for a comfortable size with clear content rather than treating the maximum upload limit as the target.

Keep a quality copy

For records, contracts, certificates and other important documents, keep the original high-quality file. Compression should create a convenient distribution copy, not replace your master document. This simple habit prevents quality loss from becoming permanent.

A practical compression workflow

For routine work, keep the original, create one compressed copy, inspect several pages and check the final file size. If the document is still too large, try a stronger setting once rather than repeatedly processing the same compressed file. This keeps the quality comparison clear and avoids unnecessary degradation.

When to use a different method

Some PDFs contain mostly vector text and graphics, while others are essentially collections of photographs. If the file is still large after reasonable compression, the underlying document may need a different workflow, such as reducing the source images before creating the PDF or exporting it with more suitable document settings.

Frequently asked questions