Compress PDF Online Free
Reduce PDF file size instantly — choose a compression level, click Compress, and download. No signup, runs entirely in your browser.
How to Compress a PDF
- 1Click the drop zone or drag your PDF file onto it. The file is read locally — nothing is sent to a server.
- 2Choose a compression level: Low for best quality, Medium for everyday sharing, or High for the smallest possible file.
- 3Click Compress PDF. Each page is rendered and re-encoded as a JPEG in your browser — a progress indicator shows which page is being processed.
- 4When complete, the file size comparison shows your original size, the compressed size, and the percentage saved. Click Download compressed PDF to save it.
Why Compress PDFs Without Uploading?
Most online PDF compressors upload your files to a remote server for processing. This raises privacy concerns for documents containing personal data, financial records, contracts, or confidential business information. This tool processes everything locally: PDF.js and pdf-lib run entirely in JavaScript inside your browser, so your files never leave your device.
Client-side compression is also faster for smaller files because there is no upload or download round-trip to a server. The compressed PDF is generated in memory and made available as an immediate local download.
When to Use Each Compression Level
| Level | Best For | Typical Size Reduction |
|---|---|---|
| Low | Professional print, legal documents, signed contracts | 10–30% |
| Medium | Email attachments, online sharing, general office use | 30–60% |
| High | Archiving, uploading to portals with strict size limits | 50–80% |
Tips for Compressing PDFs Effectively
Start with Medium
Medium compression works well for most everyday documents. Only switch to High if you still need a smaller file after trying Medium, or to Low if print quality is critical.
Scanned PDFs Compress Best
Scanned documents are already images inside a PDF wrapper. This tool re-encodes those images at a lower quality, which typically produces the largest savings — often 60–80%.
Text-Only PDFs May Not Shrink
PDFs generated directly from word processors use highly efficient text and vector encoding. Converting them to images (what this tool does) may actually increase the file size. Use a dedicated PDF optimiser for those.
Links Are Not Preserved
The output PDF contains images of each page, not structured content. Hyperlinks, form fields, and annotations from the original are not carried over. If interactivity matters, keep the original alongside the compressed version.
Remove the Password First
If your PDF is password-protected, remove the password using a PDF password remover before compressing. Encrypted files cannot be rendered for compression.
Compress Before Merging
If you plan to merge several PDFs into one document, compress each one individually first. The merged result will be much smaller than compressing after merging, especially for large multi-document bundles.
Frequently Asked Questions
How does the PDF compressor work?
The tool uses PDF.js to render each page of your PDF to a canvas element in the browser, then re-encodes each page as a JPEG image at the chosen quality level, and packs the result into a new PDF using pdf-lib. This approach reduces file size significantly — especially for scanned documents and image-heavy PDFs — by discarding visual detail that is not perceptible at normal viewing sizes.
Is my PDF uploaded to a server?
No. All processing happens locally inside your browser. Your file is never sent to any server, stored remotely, or transmitted over the network. The tool works entirely offline once the page has loaded.
What is the difference between Low, Medium, and High compression?
Low compression renders each page at a higher resolution with minimal JPEG quality loss — the output is closest to the original and suitable for printing. Medium is a balanced preset good for most everyday uses like email or sharing online. High compression renders at a lower resolution with more aggressive JPEG quality reduction, producing the smallest possible file — best for archiving or when file size matters more than pixel-perfect fidelity.
Will compressed text still be readable?
Yes, at Low and Medium settings text remains sharp and readable on screen and when printed at normal sizes. At High compression, text in complex fonts or very small point sizes may appear slightly soft. For documents that are primarily text with no images, Medium compression is recommended as a good balance.
Does compression remove or alter any content?
The tool re-renders pages as JPEG images. This means interactive elements — form fields, hyperlinks, annotations, and digital signatures — are not preserved in the output. The visual appearance of each page is preserved, but the output PDF contains images of the pages rather than the original structured content.
Can I compress a password-protected PDF?
Password-protected PDFs that require a password to open cannot be processed. If a PDF has an owner password that restricts printing or editing but does not require a password to view, it may be processed depending on the restrictions set. Remove the password first using a PDF password remover tool, then compress.
How much will the file size be reduced?
Reduction varies widely depending on the content of the PDF. Scanned document PDFs (which are already images) can be reduced by 50–80%. PDFs with embedded high-resolution photos similarly compress well. Text-only PDFs generated from word processors are already small and compact — the compressed version may actually be larger because the tool converts text to images, which are inherently larger than compressed text streams.
Is there a file size limit?
There is no server-imposed limit because no upload occurs. The practical limit is your device's available memory. Very large PDFs — 100 MB or more, or documents with hundreds of pages — may be slow to process on lower-end devices. For most typical documents (invoices, reports, presentations under 50 MB), processing completes in a few seconds.