PDF Compressor
Reduce PDF file size while preserving quality. Perfect for email attachments and uploads.
Drop PDF files here
or
Supported formats: .pdf — multiple files supported
What Is PDF Compression?
PDF compression is an online tool that reduces the file size of PDF documents. It's useful for meeting email attachment size limits, saving cloud storage space, and optimizing files for web uploads — wherever oversized PDFs are a problem.
sakutto.ai's PDF compressor uses WebAssembly technology to process everything in your browser. Your PDF data is never sent to any server, so you can safely compress confidential files like quotes, contracts, and internal documents.
Choose from three compression levels (low, standard, high) to balance quality and file size for your needs. Batch compression of multiple files is supported, making it efficient to handle large volumes of PDFs. Free, no sign-up required.
How to Compress PDFs
- Drag & drop PDF files or use the file picker to add them
- Select a compression level (Standard is recommended)
- Click "Start Compression" to compress
- Download files individually or as a ZIP archive
Features of sakutto's PDF Compressor
- Runs entirely in your browser — PDF data is never sent to a server
- Three compression levels to choose from
- Batch compression for multiple files
- No file size limit (depends on your device's memory)
- Advanced settings for fine-tuning image quality, DPI, and metadata removal
- Responsive design that works on smartphones too
- Free, no sign-up, no usage limits
Why PDF Compressor on sakutto is safe
Many online tools upload your files to external servers for processing. This tool never sends your PDF files to any server — everything is processed entirely in your browser.
* Some AI-powered tools require server-side processing. Tools that send data to a server will always notify you beforehand.
| Comparison | Typical online tools | sakutto |
|---|---|---|
| Where data is sent | Uploaded to external servers | Nowhere — processed in your browser |
| Data leak risk | Risk during transfer and server storage | No risk — no network transfer occurs |
| External traffic | File data travels over the internet | No file data appears in network logs |
| Offline use | Not possible (server required) | Works offline after initial load |
How browser-based processing works
- WebAssembly (WASM): Processes PDF files in your browser at near-native speed. No server communication occurs.
- Web Workers: Runs on a background thread separate from the main thread, so your browser stays responsive during processing.
- After processing, your browser automatically frees the data from memory. No PDF files remains outside your device.
For IT security teams: How to verify
You can verify that sakutto never sends your PDF files externally by checking the Network tab in your browser's DevTools while using the tool. You'll see that no requests involving your PDF files are made. This can also serve as documentation for your IT security team.
Frequently Asked Questions
Are my files uploaded to a server?
No. All processing is done entirely in your browser — your PDF files are never sent to any external server. You can safely use this tool even with confidential documents.
How much compression can I expect?
Compression rates vary depending on the PDF content. Image-heavy PDFs can typically be reduced by 50–80%, while text-heavy PDFs see a 10–30% reduction.
What happens to the quality after compression?
You can choose from three compression levels: "Low" maintains near-original quality through optimization, "Standard" offers the best balance of quality and file size, and "High" minimizes file size as much as possible. Text remains selectable and searchable at all levels.
How many files can I compress at once?
There is no strict limit — it depends on your device's memory. Typically, several dozen files can be compressed without issues. For very large batches, we recommend processing 10–20 files at a time.
Can I compress password-protected PDFs?
Password-protected PDFs are not currently supported. Please remove the password before using the compressor.
What's the difference between the compression levels?
"Low (High Quality)" removes metadata and optimizes streams with virtually no visible quality loss. "Standard" recompresses embedded images for an optimal balance of quality and size. "High" further reduces image quality to minimize file size as much as possible.
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