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Compress PDF Online – Reduce PDF File Size Instantly | Free
✅ 100% Free  ·  No Signup  ·  No Watermark

Compress PDF Files
Reduce Size Instantly

Upload your PDF, choose your compression level, and download a smaller file in seconds. Runs entirely in your browser — your files never leave your device.

100%
Free Forever
3
Compression Levels
0
Files Sent to Server
⚡
Instant Download
∞
Unlimited Use

🗜️ PDF Compressor — Start Here

Upload your PDF below, pick a compression level, and hit Compress. Your smaller PDF is ready in seconds.

🔐
100% browser-based — your PDF stays private. Unlike cloud compressors, this tool never uploads your file to a server. The PDF is read into memory, recompressed locally with pdf-lib, and downloaded right from your browser. Safe for confidential documents.
📂 Upload Your PDF
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Drag & Drop your PDF here

or click to browse files from your device

✅ PDF files only  ·  Any size

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↩ Change file
⚙️ Compression Level
✅ Compression Complete!
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📁 Original Size
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🗜️ Compressed Size
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💾 Space Saved
Why Use This Tool

Powerful Compression,
Zero Complexity

A clean, fast, and private PDF compressor that runs entirely in your browser — no uploads, no accounts, no risk.

🔒
100% Private
Your PDF never leaves your device. All compression happens locally in your browser using JavaScript — zero server upload.
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Instant Results
No waiting for uploads or server processing. Compression runs at full speed directly on your device and finishes in seconds.
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3 Compression Levels
Choose Low for near-lossless quality, Medium for the sweet spot, or High to squeeze every byte when size is critical.
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Before & After Stats
See exactly how much space you saved — original size, compressed size, and percentage reduction shown clearly after compression.
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Works on Any Device
Fully responsive design works seamlessly on desktop, tablet, and mobile. Compress PDFs from anywhere, any time.
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No Watermarks Ever
Your compressed PDF is clean and unmodified aside from reduced file size. No branding, no stamps, no hidden modifications.
✅
Free with No Limits
Compress as many PDFs as you want, as often as you want. No account required, no subscription, no daily limits.
🖱️
Drag & Drop Upload
Simply drag your PDF onto the page or click to browse. The interface is clean and designed to get you to your result fast.
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Instant Download
Your compressed PDF downloads immediately to your device with a single click. No email required, no link to wait for.
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Page Count Detection
As soon as you upload, the tool reads and displays your PDF's page count so you know exactly what you're compressing.
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Object Stream Optimization
Uses pdf-lib's object stream packing to remove redundant data and repackage the PDF structure more efficiently.
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Dark Mode Support
The interface automatically adapts to your system's dark mode preference for comfortable use at any time of day.
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Works Offline
After the page loads once, the compressor keeps working with no internet connection — strong proof nothing is uploaded.
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Handles Encrypted PDFs
The tool can load PDFs with basic encryption flags (ignoreEncryption) so more of your documents process successfully.
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Zero Installation
No software to download, no admin rights, no browser extensions. Open the page and it just works — even in incognito mode.
Simple Process

Compress Your PDF in 3 Steps

From upload to download in under a minute — no experience or software needed.

1
Upload Your PDF
Drag and drop your PDF file onto the tool, or click to browse and select it from your device.
2
Choose Compression Level
Select Low, Medium, or High compression depending on how much you need to reduce the file size.
3
Download Compressed PDF
Click Compress PDF and your smaller file downloads instantly. See exactly how much space you saved.
Compression Levels

Which Level Should You Choose?

Each compression level balances file size against quality differently. Here's exactly what each one does and when to use it.

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Low
Maximum Quality
  • Image quality: ~82% — near-original
  • Size reduction: Modest
  • Best for: Documents to print or archive
  • Text impact: None — text stays sharp
  • Use when: Quality matters more than size
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Medium
The Sweet Spot
  • Image quality: ~62% — very good
  • Size reduction: Balanced
  • Best for: Email attachments, web upload
  • Text impact: None — text stays sharp
  • Use when: You want a good size/quality balance
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High
Smallest File
  • Image quality: ~38% — visible softening
  • Size reduction: Maximum
  • Best for: Strict size limits, quick sharing
  • Text impact: None — text stays sharp
  • Use when: Hitting a size cap is critical
Knowledge

What Makes a PDF Large?

Understanding what bloats a PDF helps you choose the right compression level and set realistic expectations for the result.

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Images
The Biggest Culprit
  • Impact: Often 80-95% of file size
  • Cause: High-resolution scans, photos
  • Compresses: Very well — 30-70% savings
  • This tool: Recompresses embedded images
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Embedded Fonts
Sometimes Heavy
  • Impact: Can add 1-5 MB if not subset
  • Cause: Full fonts embedded, not subset
  • Compresses: Modestly via restructuring
  • This tool: Repackages document streams
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Text & Vectors
Already Efficient
  • Impact: Usually tiny
  • Cause: Text is stored very compactly
  • Compresses: Little — already small
  • This tool: Object stream optimization
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Metadata & Bloat
Hidden Overhead
  • Impact: Variable — edits accumulate
  • Cause: Revision history, redundant objects
  • Compresses: Well via re-serialization
  • This tool: Removes redundant objects on save
Who Uses This Tool

Common Use Cases

From job seekers to businesses, compressing PDFs solves countless everyday problems.

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Email Attachments
Most email providers cap attachments at 20-25 MB. Compress oversized PDFs to slip under the limit without splitting them into multiple files.
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Job Applications
Many job portals limit resume and portfolio uploads to 2-5 MB. Compress your PDF CV or portfolio to meet strict upload requirements.
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Website Uploads
Faster page loads and lower bandwidth costs. Compress PDFs before hosting them on your website so visitors download them quickly.
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Government Forms
Tax filings, visa applications, and official portals often enforce tight file-size limits. Compress scanned forms to fit the rules.
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Storage Savings
Free up space on your device or cloud storage. Compressing a large library of PDFs can reclaim gigabytes of room over time.
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Faster Sharing
Smaller files upload and download faster over slow connections. Compress before sharing via messaging apps, Drive, or Dropbox.
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Students
Assignment portals and learning platforms often limit submission sizes. Compress scanned notes, reports, and projects to fit.
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Scanned Documents
Scanners produce huge image-heavy PDFs. Compression dramatically shrinks scanned contracts, receipts, and records.
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Mobile Data Savers
Sending PDFs on a metered or slow mobile connection? Compress first to use less data and send faster on the go.
Tool Comparison

This Tool vs Alternatives

How browser-based PDF compression compares to desktop apps and cloud services.

Feature This Tool Adobe Acrobat Cloud Compressors
Cost Free forever $15-23/month Free with limits
Installation Required None Yes (~500MB) None
File Privacy 100% local Local processing PDF uploaded
Account Required No Yes (Adobe ID) Often yes
Daily Limits None None Often 2-3 free/day
Compression Levels 3 levels Multiple presets Usually 1-2
Before/After Stats Yes Limited Varies
Watermark Never Never Often on free tier
Setup Time Zero seconds Install + activate Often account signup
Best For Quick private compression Pro editing + deep optimization One-offs without installs
Pro Tips

Tips for Best Results

Get the most out of PDF compression with these practical tips.

TIP 01
Image-heavy PDFs shrink most
PDFs full of scanned pages or photos can shrink 30-70%. Text-only PDFs are already compact and won't reduce much — that's normal.
TIP 02
Start with Medium
Medium is the sweet spot for most documents. Try it first, check the result, then move to High only if you need a smaller file.
TIP 03
Use Low for printing
If you'll print the PDF or archive it long-term, use Low compression to keep image quality high. Size matters less for these uses.
TIP 04
High for strict size caps
When a portal demands "under 2 MB" or similar, use High compression. The slight quality trade-off is worth meeting a hard limit.
TIP 05
Text stays sharp at every level
Compression only affects images — your text remains crisp and fully selectable at Low, Medium, and High. Only photos and scans soften.
TIP 06
Check the before/after stats
After compressing, review the space-saved percentage. If it's tiny, your PDF was already efficient — no need to try a higher level.
TIP 07
Scanned docs benefit most
Scanners produce bloated image-based PDFs. These are the ideal candidates for compression — you'll often see dramatic size reductions.
TIP 08
Re-compressing rarely helps
Once a PDF is compressed, running it through again gives little extra benefit and may degrade quality. Compress from the original when possible.
TIP 09
Big files need patience
A 100 MB+ PDF takes longer to process since everything runs on your device. The progress bar keeps moving — don't close the tab.
TIP 10
Desktop beats mobile for big files
For very large PDFs, a desktop browser with more memory processes faster and more reliably than a phone or tablet.
Under the Hood

How the Compression Works

For curious users and developers — here's the technical pipeline behind the compression.

STEP 1
Read PDF
Your PDF is read by the browser's arrayBuffer() API into memory — entirely on your device, never uploaded anywhere.
STEP 2
Load with pdf-lib
The pdf-lib library parses the document structure with ignoreEncryption enabled so more files load successfully.
STEP 3
Read Page Count
The number of pages is read with getPageCount() and shown to you, so you know the scope of the document being processed.
STEP 4
Enumerate Objects
The tool walks all indirect objects via enumerateIndirectObjects() to locate embedded image streams (XObjects of subtype Image).
STEP 5
Identify Images
For each image, the tool reads width, height, color space, and bits-per-component from the stream dictionary to assess it for recompression.
STEP 6
Canvas Recompression
Images are drawn to an HTML5 canvas and re-encoded as JPEG at your chosen quality level via canvas.toBlob().
STEP 7
Object Stream Packing
The document is re-serialized with useObjectStreams: true, which packs objects efficiently and removes redundant data.
STEP 8
Compare Sizes
The new file size is compared to the original, and the percentage saved is calculated and displayed in the results card.
STEP 9
Blob Download
The compressed bytes are wrapped in a Blob, given a temporary object URL, and downloaded with a single click — no server involved.
Troubleshooting

Common Issues & Fixes

Running into trouble? Most issues fall into one of these categories — here's how to identify and fix them.

📊
My file barely got smaller
What it means: Your PDF is mostly text and vectors, which are already highly compressed. What to do: This is normal and expected — text-based PDFs have little room to shrink. The biggest savings come from image-heavy or scanned documents.
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"Could not compress this PDF"
What it means: The PDF is strongly encrypted, corrupt, or uses an unusual structure. What to do: Open it in a PDF reader and re-save or Print to PDF to create a clean copy, then try compressing that version.
🖼️
Images look soft after compression
What it means: You used High compression, which trades quality for size. What to do: Re-compress the original at Medium or Low for sharper images. Always compress from the original PDF, not the already-compressed one.
⏱️
Compression is slow on a big file
What it means: Large PDFs (100 MB+) take time since all processing runs on your device. What to do: Be patient — the progress bar advances. Close other tabs to free memory, and use a desktop browser for very large files.
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Download doesn't start
What it means: Your browser may be blocking automatic downloads. What to do: Check the notification area for a download prompt. In Safari, allow downloads in Site Settings. Try Chrome, Firefox, or Edge if issues persist.
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Page count not showing
What it means: The PDF may have an unusual structure that pdf-lib can't read fully. What to do: Compression may still work — just hit Compress. If it fails, re-save the PDF through a reader first to normalize its structure.
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Password-protected PDF
What it means: The file has user-password encryption that can't be bypassed. What to do: Open it in your PDF reader with the password, then Print to PDF to create an unprotected copy, and compress that.
📱
Browser crashes on large files
What it means: The PDF is using all available browser memory. What to do: Restart the browser, close all other tabs, and try again. For files above 200 MB, use a desktop browser with plenty of RAM.
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"Optimised" instead of a percentage
What it means: The compressed file wasn't smaller than the original — the PDF was already optimized. What to do: Nothing needed. Your file is already as small as it practically gets; use the original or the result, whichever you prefer.
🌐
Tool won't load
What it means: The pdf-lib library failed to load from the CDN. What to do: Check your internet connection and refresh the page. The library loads once on first visit, then the tool works offline.
Privacy First

Your PDF Never Leaves Your Browser

Unlike cloud-based PDF compressors that upload your files to remote servers, this tool runs entirely in your web browser. Here's exactly what happens — and what doesn't.

🔐
Zero Server Communication
When you upload a PDF, its bytes are read by JavaScript running in your browser. pdf-lib parses and recompresses the document, and the result downloads directly — all on your device, in memory. No file content is ever transmitted over the network.
✅ No file uploads ✅ No tracking pixels ✅ No account required ✅ No cookies stored ✅ No analytics on content ✅ Works offline after first load
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Verify It Yourself
Open your browser's developer tools (F12), go to the Network tab, and watch what happens when you upload and compress. You'll see no outbound requests with your PDF's content.
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Works Offline
After the page first loads, you can disconnect from the internet and the compressor still works. This is the strongest possible proof that your files aren't being uploaded.
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Transparent Code
All compression logic is in plain JavaScript visible in your browser's View Source. You can audit exactly what the tool does — no hidden processing, no obfuscated code.
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No Retention
When you close the browser tab, all traces of your PDF are gone. The data lives only in your browser's memory during the active session.
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Safe for Sensitive Documents
Because nothing is uploaded, this tool is safe for confidential PDFs — contracts, financial reports, medical records, internal memos. Your data never reaches anyone else's infrastructure.
🛡️
No Third Parties
The pdf-lib library is loaded from a public CDN at page load, but it runs locally. No analytics, no ad networks, no data brokers receive your file content.
FAQ

Frequently Asked Questions

Everything you need to know about our free PDF compressor.

Is this PDF compressor really free?
Yes, completely free with no hidden fees, no subscriptions, and no limits on how many PDFs you compress. No account needed.
Is my PDF uploaded to a server?
No. All compression happens locally in your browser using JavaScript. Your PDF file never leaves your device, so your documents stay 100% private.
How much will the file size be reduced?
Results vary depending on PDF content. Image-heavy PDFs often see 30–70% reduction. Text-only PDFs tend to compress less as they are already efficient.
Will compression reduce quality?
Low compression retains near-original quality. Medium offers a balanced result. High compression prioritises size reduction and may affect image sharpness slightly.
What is the maximum file size supported?
There is no fixed server-side limit since processing is local. Very large PDFs (100MB+) may take longer depending on your device's processing speed.
Does it work on mobile and tablet?
Yes, the tool is fully responsive and works on all modern smartphones, tablets, and desktop computers without any app installation.
Does compression affect my text?
No. Text stays sharp, selectable, and searchable at every compression level. Only embedded images are recompressed — text and vectors are untouched.
Which compression level is best?
Medium is the best starting point for most documents. Use Low for printing or archiving, and High when you need to hit a strict file-size limit.
Can I compress a password-protected PDF?
If it opens without a password, yes. For files requiring a password to open, remove the password first by opening it and printing to a new PDF.
Does it work offline?
Yes, after the page loads once. The pdf-lib library is fetched on first load, after which the compressor works without an internet connection.
Is there a watermark on the output?
No, never. Your compressed PDF is completely clean — no watermarks, no logos, no added pages. The only change is reduced file size.
Can I compress the same PDF again?
You can, but it rarely helps much and may reduce quality further. For best results, always compress from the original uncompressed PDF.
Will it work on scanned documents?
Yes — and scanned PDFs are ideal candidates. They're image-heavy, so they often see the biggest size reductions of all document types.
Does it reduce the number of pages?
No. Compression reduces file size, not page count. Every page in your original PDF is preserved in the compressed output.
What browsers are supported?
All modern browsers — Chrome, Firefox, Safari, Edge, Opera, Brave. Internet Explorer is not supported. The tool uses standard web APIs available since 2015.
Is the compressed PDF still editable?
Yes. The output is a standard PDF you can open, annotate, and edit in any PDF editor. Compression only optimizes file size, not editability.
Why did my file say "Optimised"?
That means the result wasn't smaller than the original — your PDF was already well-optimized. There's simply no further meaningful reduction available.
Can I use it for commercial work?
Yes. There are no restrictions on how you use the compressed files. The output is entirely yours for personal or commercial use.
Does it keep my PDF's bookmarks and links?
In most cases yes, since the document structure is preserved during re-serialization. Very complex interactive features may occasionally be simplified.
How is this different from zipping a PDF?
Zipping wraps the file without reducing its internal size much, and recipients must unzip it. This tool recompresses the PDF's contents so the PDF itself is smaller and stays a normal PDF.

Ready to Shrink Your PDF?

Scroll back to the top, drop your PDF into the upload zone, pick a compression level, and download a smaller file in seconds. No signup, no software install, no waiting.

🗜️ Start Compressing Now
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