How to Compress a PDF Online for Free (Without Losing Quality)
Learn how to reduce PDF file size online in seconds. Step-by-step guide with free tools — no software installation needed.
Why PDF Files Get So Large
PDF files grow large for several reasons: embedded high-resolution images, embedded fonts, metadata, and annotations all add to the file size. A single scanned page at 300 DPI can easily be 1–2 MB on its own. A 20-page report with images can quickly reach 50 MB — too large to email or upload.
The good news: most of that size can be removed without any visible quality loss.
How PDF Compression Works
PDF compression works in two main ways:
Structure optimisation removes unused objects, duplicate data, and redundant metadata from the file. This is fast and lossless — the document looks identical after compression.
Image re-rendering redraws each page at a lower resolution and re-encodes images at reduced quality. This achieves much higher compression ratios (often 50–80%) but is best used when the PDF is image-heavy or was originally scanned.
How to Compress a PDF on Breklo
1. Go to Breklo's Compress PDF tool
2. Drag and drop your PDF file, or click Browse files
3. Choose a compression level:
- Basic — fast structural optimisation, no quality change
- Medium — re-renders pages at 72% quality, good for most documents
- High — maximum compression, best for scanned PDFs
4. Click Compress PDF
5. Your compressed file downloads automatically
The tool shows you the exact reduction — original size, new size, and percentage saved.
Tips for Best Results
- For text-only PDFs (contracts, reports), use Basic mode. It's lossless and still removes 10–30% of file size.
- For scanned documents or image-heavy PDFs, use High mode. Expect 50–80% reduction.
- If you need to email a PDF, Medium mode is the sweet spot — good quality, much smaller file.
- After compressing, you can also merge multiple PDFs into one compressed document.
What About Password-Protected PDFs?
If your PDF is password-protected, you will need to unlock it before compressing. You can use a dedicated PDF unlocker tool first, then compress the result.
Frequently Asked Questions
See the FAQ section on the Compress PDF page for answers to the most common questions.
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Frequently asked questions
Does compressing a PDF reduce image quality?
It depends on the mode. Basic compression is lossless — no quality change. Medium and High modes re-render pages as images, which reduces quality slightly in exchange for much smaller file sizes. For most use cases, Medium mode is unnoticeable.
How much can I reduce a PDF file size?
Typical results range from 20% reduction (Basic, text-only PDFs) to 80% reduction (High mode, scanned or image-heavy PDFs). Results vary by document type.
Is there a file size limit?
Breklo supports PDFs up to 100 MB. All processing happens in your browser, so there are no server-side limits.
Will the compressed PDF look different?
In Basic mode, the PDF is visually identical. In Medium and High modes, text-based pages may show slight softening, but for screen reading it is generally unnoticeable.
Can I compress a scanned PDF?
Yes. High compression mode is specifically effective for scanned PDFs, as it re-renders each page at a lower DPI.
Is my PDF uploaded to a server?
No. All processing happens entirely in your browser using WebAssembly. Your file never leaves your device.