Compress PDF
Reduce PDF file size by re-optimizing the document structure. Works best on PDFs with redundant data. All processing is local — no uploads.
Click or drag a PDF here
Supports any PDF file
Note: This tool re-optimizes PDF object streams. Results vary — PDFs with images may not reduce significantly without image resampling.
Compress PDF Files Free Online
Large PDF files cause problems. They are slow to email, get rejected by upload portals, and take up storage space. A PDF compression tool solves this by reducing the file size without replacing the document or changing its layout. The same text, the same pages, the same structure — just a smaller file.
PDF compression works by removing redundant data inside the file structure. This includes duplicate font definitions, embedded metadata, unused objects, and over-sized image data stored in the PDF. After compression, the visible content stays the same while the file becomes lighter.
This tool compresses your PDF directly inside your browser. No file is sent to any server. You see the original size and the compressed size before you download the result.
How PDF Compression Works
A PDF file is made of objects: pages, fonts, images, annotations, bookmarks, and metadata. Some of these objects contain duplicate or unnecessary data. Compression identifies and removes that extra data to produce a leaner file.
Image compression is the biggest factor. Images embedded in PDFs are often stored at full resolution even when the displayed size is much smaller. Compressing those images to a lower resolution can cut file size dramatically, especially in scanned documents and presentation PDFs.
Text-based PDFs compress less because the text itself is already small. The font data and page structure make up most of the size. Removing unused font subsets and cleaning the object tree reduces the file size modestly but reliably.
This tool uses PDF-lib to re-process your document in the browser. The rewritten PDF is smaller because the library outputs a clean, optimized structure that removes the accumulated overhead from the original file creation process.
How to Compress a PDF Step by Step
Step 1 – Upload your PDF. Click the upload area or drag your PDF onto it. The tool displays the original file size immediately.
Step 2 – Wait for processing. The tool reads the file, optimizes the structure, and rebuilds the PDF in your browser. This takes a few seconds for most files.
Step 3 – Review the result. The compressed file size is shown alongside the original. You can see exactly how much space was saved.
Step 4 – Download. Click the download button to save the compressed file to your device. The original remains unchanged.
When You Need to Compress a PDF
Email attachments. Most email providers limit attachment sizes to 10 MB or 25 MB. A large PDF may need compression before it can be sent.
Online form uploads. Government portals, university admissions, and HR systems often limit file uploads to 2 MB or 5 MB. Compression lets your document meet those limits.
Website uploads. PDFs used as downloadable resources on websites should be small so they load quickly for visitors.
Cloud storage. If you store many PDFs in Dropbox, Google Drive, or OneDrive, compression reduces your storage usage.
Mobile sharing. Sending PDFs over messaging apps like WhatsApp has file size limits. Compression keeps your file within those limits.
After merging PDFs. When you combine multiple PDFs with our Merge PDF tool, the combined file is larger. Compressing after merging brings the size back down.
Benefits of Compressing PDF Files
Faster sharing. Smaller files upload and download faster, saving time for both sender and recipient.
Meets file size limits. Many platforms enforce strict upload limits. Compressed PDFs fit within those limits without sacrificing content.
Lower storage costs. Storing thousands of compressed documents uses less disk space and reduces cloud storage fees.
Better user experience. PDF downloads from websites load faster when the files are smaller. This improves the experience for your audience.
No software required. You can compress PDFs in your browser without installing Adobe Acrobat or any other application.
Limitations of Browser-Based PDF Compression
Compression ratios vary. Text-heavy PDFs may only compress by 10 to 20 percent. Image-heavy PDFs can compress by 50 percent or more. Results depend on the source content.
Already-optimized files. If a PDF was created by a professional tool and is already well-optimized, further compression may not reduce the size significantly.
No image quality control. This tool applies a standard optimization pass. For precise control over image resolution and quality settings, a desktop tool like Adobe Acrobat Pro gives more options.
Large files are slow. PDFs over 100 MB may take longer to process depending on your device. Processing still completes, but you may need to wait.
Password protection. Encrypted PDFs cannot be compressed without first removing the password.
Related PDF Tools on Kwebby
- Merge PDF – Combine files before compressing the result.
- Split PDF – Remove unwanted pages to reduce file size before compression.
- JPG to PDF – Create a PDF from images at a controlled file size.
- PDF to JPG – Convert pages to images for lightweight sharing.
- Encrypt PDF – Password-protect your compressed file.
Frequently Asked Questions About PDF Compression
Does compressing a PDF reduce its quality?
It depends on the content. For text PDFs, compression removes metadata and optimizes structure without any visible change. For image-heavy PDFs, heavy compression may slightly reduce image sharpness.
Is this tool free?
Yes. You can compress as many PDFs as you like at no cost. No account is needed.
Are my files uploaded to a server?
No. Compression happens entirely in your browser. Your files never leave your device.
How much can a PDF be compressed?
It varies. Scanned PDFs and image-heavy documents often compress by 50 to 80 percent. Text documents may only compress by 10 to 30 percent.
Why is my PDF barely smaller after compression?
Some PDFs are already optimized. If the file contains mostly text with efficient fonts, there is little extra data to remove. Try splitting the document or reducing the number of pages instead.
Can I compress a password-protected PDF?
No. Remove the password first, then use this tool to compress the file.
Does this work on phones?
Yes. The tool works in Chrome, Safari, and Firefox on Android and iOS devices.