Free Online Tool

PDF Compressor

Reduce PDF file sizes by up to 90% using WebAssembly in your browser. Preserves text and fonts — only re-encodes images. Encrypted PDFs supported.

No File Storage

WASM In-Browser

No Sign-up

Why Use Our PDF Compressor?

Built for speed and quality — compresses in your browser without compromising what matters.

True Browser-Based WASM Compression

Compression runs on dedicated WebAssembly workers in your browser — one per CPU core for maximum speed. No server queues, no upload delays.

Your File Never Leaves Your Device

All compression processing happens locally using WebAssembly. Your PDF is never sent to any server for compression. Encrypted files are securely unlocked on our server, processed in memory, then returned immediately.

Two Precision Compression Modes

By Quality preserves all text and compresses embedded images. By Size flattens every page to hit an exact KB or MB target — ideal for scanned documents.

Parallel Page Processing

Multi-page PDFs are processed across multiple CPU cores in parallel — a 50-page document compresses as fast as possible on your hardware.

Completely Free, No Watermarks

No account required, no watermarks added to your output, no limits on how many times you use it. Free forever.

How to Compress a PDF

Three steps to a smaller, shareable PDF.

Upload Your PDF

Drag and drop your PDF onto the tool area or click to browse. Encrypted PDFs are detected automatically and a password prompt appears.

Choose Compression Mode

Select By Quality to shrink embedded images while keeping text fully intact, or By Size to enter an exact target file size in KB or MB.

Download Your Compressed PDF

Click Compress PDF. WebAssembly workers process your file page by page and the compressed PDF downloads automatically when done.

Who Needs PDF Compression?

Anyone dealing with large PDF files benefits from faster sharing and lower storage costs.

Email Attachments Under the Limit

Gmail, Outlook, and most email services cap attachments at 10–25 MB. Compress large PDFs to reliably fit under those limits without recreating the document.

Faster Web Page Loading

PDFs embedded in web pages or linked for download load significantly faster when optimized. Reduce a 10 MB brochure to under 1 MB without visible quality loss.

Cloud and Drive Storage Savings

Compress PDFs before uploading to Google Drive, Dropbox, or OneDrive to save storage space and make syncing faster across devices.

Document Archive Management

Compress years of archived scanned documents to free up significant disk or backup storage while keeping files accessible and readable.

Submission Portal Requirements

Many government portals, job application systems, and university submissions have strict file size limits. Compress to meet them without losing document content.

Frequently Asked Questions

Everything you need to know about our PDF compressor.

Our tool uses WebAssembly (WASM) — a near-native binary format that runs in your browser at close to CPU speed. For "By Quality" mode, it scans all embedded image streams in the PDF and re-encodes them at your chosen quality. For "By Size" mode, each page is rendered to a canvas and recompressed as an image to fit within your target file size.

"By Quality" keeps the text, fonts, hyperlinks, and vector content in your PDF completely intact — it only recompresses embedded images. This is the recommended mode for documents with both text and graphics. "By Size" renders every page as an image to hit a specific KB or MB target, achieving more aggressive compression, but text will no longer be selectable after this mode.

If you use "By Quality" mode, yes — all text, fonts, hyperlinks, and vector graphics are fully preserved and remain selectable. In "By Size" mode, each page is converted to an image, so text will appear visually but cannot be selected, copied, or searched.

Yes. The tool detects the encryption and asks for your password. The file is securely transmitted to our server over HTTPS and unlocked in memory. The unlocked file is immediately returned to your browser for compression — we never store the file, write it to disk, or retain it after the operation. Compression then happens entirely in your browser.

Since compression runs in your browser using WebAssembly, the practical limit is your device memory. Most devices handle PDFs up to 50–100 MB without issues. Very large files with many high-resolution images may take 30–60 seconds to process.

Results vary depending on the content. PDFs with many high-resolution images can often be reduced by 70–90%. Text-only PDFs with no embedded images may see only 5–15% reduction since there is little image data to compress.

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PDF Compression: The Complete Guide

PDF files grow large primarily because of high-resolution embedded images, unoptimized image streams, and redundant metadata. Our free PDF compressor uses WebAssembly — running parallel workers directly in your browser — to reduce file size dramatically without touching text, fonts, or vector graphics.

By Quality Mode: Preserve Text, Compress Images

The By Quality mode scans all embedded image streams in the PDF and re-encodes them at the quality percentage you choose. Text, fonts, hyperlinks, form fields, and vector graphics are completely preserved and remain fully selectable and searchable. This is the right mode for most documents — reports, contracts, brochures, and presentations.

By Size Mode: Hit an Exact Target

The By Size mode renders every page of the PDF to a canvas image and recompresses each page image to fit within your target KB or MB budget. This achieves significantly more aggressive compression but converts the entire document to flat images — text will appear correctly but cannot be selected, copied, or searched. Use this mode for scanned documents where text was never selectable anyway, or when you need to meet a strict upload size limit.

How Encrypted PDFs Are Handled

If your PDF is password-protected, you will be prompted to enter the password. The file and password are securely sent to our server over HTTPS, where the encryption is removed in memory using industry-standard tools. The unlocked file is immediately streamed back to your browser for compression — we never write your file to disk, log its contents, or retain it after the operation. All compression then happens entirely on your device.

Tips for Best Compression Results

For text-heavy documents with a few images, try By Quality at 60–70% first — this typically reduces size by 40–60% with no visible quality change.
For scanned documents (where pages are already images), By Size mode is far more effective than By Quality.
If your PDF is already heavily compressed, the gains from further compression will be minimal — the tool will indicate if the output is not significantly smaller.
Compressing before merging multiple PDFs makes the final combined file much more manageable.