PDF Compressor
Compress PDF online free — reduce PDF file size in your browser without uploading. Shrink large documents, scanned PDFs, and image-heavy reports instantly. No sign-up, no watermarks.
Drop PDFs here, or click to browse
PDF files · Any size · No limit
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Medium is a good default. Image-heavy PDFs compress the most.
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What is a PDF compressor?
A PDF compressor is a tool that reduces the file size of a PDF document while keeping its content — text, images, and layout — intact. This free online PDF compressor runs entirely in your browser, so you can compress PDF online without uploading anything to a server. It removes hidden overhead — metadata, embedded thumbnails, unused objects — and re-encodes embedded images at a smaller size, shrinking your PDF without changing how it looks.
Unlike most online PDF compressors that route your documents through a cloud server, this browser PDF compressor processes everything locally. That means faster results, no privacy risk, and no file-size restrictions imposed by an upload limit. It is the only secure PDF compressor that can genuinely claim your documents never leave your device.
How PDF compression works
PDF files accumulate size from several sources: high-resolution embedded images, redundant metadata (author, creation software, XMP packets), embedded preview thumbnails, and inefficient internal stream encoding. A PDF optimizer targets each of these separately to achieve the best overall PDF size reduction.
Metadata removal
Every PDF carries a metadata dictionary — title, author, creation date, editing software, XMP packets, and color profile data. This information is invisible when you open the file but can add tens of kilobytes to small documents. The compressor strips all non-essential metadata during processing.
Embedded image optimization
Embedded photos are the single largest contributor to PDF file size in most real-world documents. The compressor re-encodes each JPEG image at a lower quality factor — a technique identical to what any PDF optimizer uses. On Medium, the quality loss is imperceptible. On High, fine photographic detail is reduced but the document remains fully readable.
Thumbnail cleanup
PDF readers often embed a low-resolution thumbnail of the first page inside the file for quick previews. This thumbnail is a duplicate that adds file weight without affecting the document content. Removing it is safe — the PDF reader regenerates the thumbnail on demand.
Document stream optimization
PDF internals are structured as a series of compressed streams. When a document has been edited and re-saved multiple times, it accumulates orphaned object references and redundant cross-reference tables. Re-writing the file linearizes and compacts these streams, contributing to a further reduction in PDF size.
Reduce PDF size without losing quality
The key to reducing PDF file size without losing quality is targeting the right elements. Text, fonts, and vector graphics are never re-encoded — they stay pixel-perfect at any zoom level. Only raster images (photographs, scanned pages) are recompressed, and only at quality levels the human eye cannot distinguish from the original on screen.
- Smart image recompression. JPEG quality is lowered just enough to shrink the file — typically to 75–85% of the original quality, which is perceptually lossless for most photos.
- Text and vector retention. Fonts, outlines, and SVG-style paths are compressed using lossless methods. Printed text will look identical before and after.
- Quality preservation on Medium. The Medium preset is tuned so that the output looks identical to the input when viewed on screen or printed at standard sizes.
- Compression tradeoffs. High compression trades some image clarity for maximum size reduction — ideal for email attachments or web-facing documents, not for printing or archiving.
Why compress PDF files?
- Faster uploads and downloads. A compressed PDF transfers in a fraction of the time — critical for mobile connections and slow networks.
- Smaller email attachments. Most email providers cap attachments at 25 MB. Compressing a large PDF keeps it well under that limit without sending a download link.
- Easier file sharing. Sharing via Slack, WhatsApp, WeTransfer, or a CMS is seamless when files are lean. Compressed PDFs open faster on the recipient's end too.
- Reduced storage costs. Archiving hundreds of reports, contracts, or invoices at reduced size cuts cloud storage bills and frees local disk space.
- Better workflow efficiency. Smaller files move faster through review pipelines, e-signature platforms, and document management systems.
- Web performance. PDFs embedded in web pages or offered as downloads load significantly faster when their file size is optimized.
Compress large PDF files
Large PDFs are the most common reason people search for a PDF file size reducer. They come from a handful of sources, and understanding which applies to your document helps you pick the right compression strategy.
Reports and business documents
Annual reports, white papers, and pitch decks are often assembled in InDesign or PowerPoint with placed high-resolution images. A single 300 DPI photo can be 3–5 MB inside the PDF. Compress these on Medium to bring a 40 MB report down to under 10 MB without any visible change when read on screen.
Scanned PDFs
Scanned documents are pages photographed at high DPI and stored as images inside a PDF wrapper. They are the heaviest PDF type — a 10-page scan can easily exceed 20 MB. Because the entire content is image data, the online PDF compressor achieves its biggest reductions here: often 50–70% on High, and 30–50% on Medium with no visible degradation of text readability.
Presentation PDFs
PowerPoint and Keynote exports embed full-resolution images on every slide. A 50-slide deck can run to 100 MB. Compressing it on Medium typically brings that to 15–25 MB while keeping all the photos sharp enough for projection or screen display.
Image-heavy PDFs
Product catalogs, real estate listings, and photography portfolios saved as PDFs are primarily image data. This compress large PDF tool handles them in your browser regardless of how many pages they contain, with no upload size limit.
Privacy & security — your files never leave your device
This is a genuinely secure PDF compressor. The tool runs 100% in your browser: there are no file uploads, no cloud processing, no temporary server storage, and no tracking of document contents. When you drop a PDF onto the page, it is read directly from your local disk by your browser's File API and processed in memory using JavaScript. The compressed output is written back to your disk. Nothing travels over the network.
- No upload required. The page loads once; after that, you can disconnect from the internet and it still works.
- No server storage. There is no API endpoint receiving your files. No server ever sees your document.
- No cloud dependency. Processing happens in your browser's JavaScript runtime — entirely on your hardware.
- No user tracking of content. Analytics measure page visits, not what files you process or what they contain.
This makes it safe to compress PDF without upload for contracts, medical records, legal filings, financial statements, NDA-protected documents, and any material that cannot leave your machine.
Compression levels explained
Choose the compression level that matches how you will use the output document:
| Level | Quality | Size Reduction | Best For |
|---|---|---|---|
| Low | Highest | Small (10–25%) | Official documents, legal filings, archives |
| Medium | Balanced | Medium (30–60%) | General sharing, email, business reports |
| High | Lower | Maximum (50–75%) | Web uploads, previews, large scanned PDFs |
Supported PDF types
This PDF compression tool handles the full range of standard PDF documents:
- Text PDFs. Generated from Word, Pages, or LibreOffice — minimal size reduction, but metadata and embedded thumbnails are stripped.
- Scanned PDFs. Pages photographed or photocopied — highest compression potential because the entire content is image data.
- Image PDFs. Photo books, product catalogs, portfolios — compress each embedded image to reduce the total document size.
- Business documents. Invoices, contracts, reports — typically mixed content; Medium is the safest preset.
- Presentation PDFs. PowerPoint and Keynote exports — image-heavy and highly compressible.
- Multi-page PDFs. No page limit. Compress documents with hundreds of pages entirely in your browser.
Password-protected PDFs cannot be compressed until they are decrypted. Need to convert iPhone HEIC photos into a PDF first? Use the HEIC to PDF tool, then compress the result here.
How to compress a PDF
- 1
Add your PDF files
Drag and drop one or more .pdf files onto the drop zone, or click to browse. No file-size limit — add as many documents as you need.
- 2
Pick a compression level
Low keeps the highest quality, Medium is the balanced default, High squeezes the file size the hardest. Choose based on how the PDF will be used.
- 3
Compress and download
Click Compress. Each PDF is processed entirely in your browser — files never leave your device. Download instantly or grab all files as a ZIP.
PDF Compressor — frequently asked questions
How can I compress a PDF online for free?
Upload your PDF to this free PDF compressor, choose a compression level (Low, Medium, or High), and click Compress. Your PDF is reduced in your browser in seconds — no account, no payment, no watermarks required.
How much can a PDF be compressed?
It depends on the content. Image-heavy PDFs — reports with photos, scanned documents, presentation slides — typically shrink 40–70%. Text-only PDFs compress only 1–10% because text data is already compact. On average, most real-world PDFs reduce by 30–50%.
Does PDF compression reduce quality?
Text and vector graphics are never touched — they remain perfectly crisp. Only embedded JPEG images are re-encoded at a slightly lower quality setting. On the Medium preset, the difference is invisible to the naked eye for most documents.
Is online PDF compression safe?
This PDF compressor is 100% browser-based. Your files are never uploaded to any server, stored in the cloud, or transmitted anywhere. All processing happens locally on your device using JavaScript, making it safe for confidential contracts, medical records, and personal documents.
What is the best PDF compression level?
Medium is the best default for most use cases — it cuts file size by 30–60% while keeping quality indistinguishable from the original. Use Low for official documents where every pixel matters. Use High for web uploads or email attachments where size is the priority.
Why is my PDF file so large?
Large PDF files usually contain high-resolution embedded images (photos, scanned pages), embedded fonts, XMP metadata, and preview thumbnails. A PDF compressor strips this overhead and re-encodes images at a smaller size, which is why image-heavy PDFs shrink the most.
Can I compress scanned PDFs?
Yes. Scanned PDFs are essentially image files packaged inside a PDF container. Because they are entirely made of images, they compress more aggressively than text PDFs — often 50–70% on the High setting. The tradeoff is that High compression can soften fine scan details.
How do I email large PDF files?
Compress the PDF here first, then attach it. Most email providers cap attachments at 25 MB. Running a large PDF through this compressor on Medium will typically bring a 20–30 MB document well under that threshold without visible quality loss.
Can I compress a password-protected PDF?
No. Encrypted PDFs cannot be processed without the password. Remove the password protection first (using your PDF reader or Adobe Acrobat), then compress the unlocked file here.
Is there a file-size limit?
No hard limit. Very large PDFs (100 MB and up) may take a few seconds to process depending on your device, but everything still runs locally in your browser with no upload caps.
How does the PDF compressor work technically?
The compressor runs in your browser using JavaScript. It parses the PDF binary, strips metadata (title, author, XMP data, embedded thumbnails), and re-encodes embedded JPEG images at a lower quality factor. No file is ever sent to a server.
Can I compress multiple PDFs at once?
Yes. Drop multiple PDF files at once and they are all compressed in parallel. Download each file individually or click Download All to get a ZIP archive containing every compressed PDF.
How do I compress a PDF on iPhone without an app?
Open this page in Safari on your iPhone — no app download or sign-up needed. Tap the drop zone to open the Files app picker and select your PDF. Choose a compression level (Medium works well for most documents), then tap Compress. The compressed file downloads directly to your Downloads folder in the Files app. The tool works on any iPhone running iOS 14 or later. Because the compression runs entirely in Safari, your document is never sent to any server.
How do I compress a PDF to under 1 MB?
Start with the High compression level — it applies the most aggressive image recompression and strips the most metadata. If the output is still above 1 MB, the PDF is likely a scanned document with many pages, each stored as a high-resolution image. In that case, try splitting the PDF into smaller sections first (print selected pages to a new PDF), compress each section separately, then merge the compressed sections using the Merge PDF tool. For single-page PDFs like invoices or certificates, Medium compression almost always brings the file under 1 MB.
Why does my PDF look blurry or pixelated after compression?
Blurriness after compression is caused by the High preset recompressing embedded images at a significantly lower quality. This is most noticeable in scanned documents where the text is stored as an image rather than real text. To fix this: re-compress the original file at Low or Medium instead of High. If you only have the blurry compressed version, there is no way to recover the original detail — always keep a backup of the original PDF before compressing. For official documents where text readability is essential, the Low preset is the safest choice.
Does compressing a PDF affect its digital signature or form fields?
This compressor does not modify digital signatures, form field data, annotations, or interactive elements — it only targets metadata and embedded raster images. However, some PDF security schemes invalidate the signature if any byte of the file changes, which compression will do. If your PDF has a legally binding digital signature that must remain valid, do not compress it. For PDFs with fillable form fields (without signatures), compression is generally safe — the fields remain interactive after processing.
How do I share a large PDF on WhatsApp?
WhatsApp has a 100 MB file size limit for documents (16 MB for older versions of the app in some regions). Compress the PDF here on Medium first — most documents shrink by 30–60%, which easily brings them under the limit. In WhatsApp, send the file using the paperclip → Document option rather than the image picker, so WhatsApp does not apply additional image compression. If the PDF is still too large after compression, consider splitting it and sending in parts, or sharing via Google Drive or iCloud Drive and sending the link instead.