100% local: total privacy

Compress PDF for free, without uploading your files.

Shrink your PDF files directly in your browser, free and with no account required, for maximum privacy. Your documents never leave your computer: no server, no upload.

Why use CocoonPDF

How it works

Drop one or more PDFs, pick a compression level, and download the result a few seconds later: no extra steps.

Adjustable quality

Three ready-made levels (Light, Balanced, Strong) plus advanced settings (DPI, JPEG quality, font subsetting) to balance size and quality for your document.

Simple to use

No account to create, no software to learn: drag your file in, click Compress, download. That's it.

Works on every device

CocoonPDF runs entirely in your browser: Windows, macOS, Linux, iPhone, or Android, nothing to install for your system.

No install, no server

Unlike typical "online" tools, your files are never sent to a server to be compressed: all the processing happens right on your device.

Private by design

Since nothing ever leaves your device, there's nothing to store or later delete from a remote server: your documents stay with you, from the first byte to the last.

How to compress a PDF properly: the complete guide

Compressing a PDF means shrinking its size without sacrificing (too much) quality. In practice, that means resampling images to a lower resolution, re-encoding them as JPEG at an adjusted quality level, and stripping out anything that isn't essential to how the document displays. Here's how it actually works, and how to pick the right settings for your document.

What actually happens during compression

A large PDF is almost always large because of its images, not its text: a page of text weighs a few kilobytes, while a single high-resolution scanned page can weigh several megabytes on its own. CocoonPDF targets embedded images first: they're resampled to a target resolution (expressed in DPI, dots per inch) and re-encoded as JPEG at a chosen quality level. The higher the DPI and quality, the closer the image stays to the original, and the heavier the file remains. Text itself is never rasterized or degraded: it stays sharp, selectable, and printable at any level, unless you explicitly enable the "Rasterize complex pages" option.

Which level to pick for your use case

CocoonPDF offers three presets. "Light" (200 DPI, 85% quality) suits archiving or future printing: the loss is nearly invisible, and the size reduction stays modest. "Balanced" (144 DPI, 75% quality) is the right default for emailing or sharing online: more than enough on screen, with a clear drop in file size. "Strong" (96 DPI, 50% quality) aims for the smallest possible size, for bulky documents that need to fit under a size limit no matter what (an email attachment, an online form); the loss becomes visible on image-heavy documents, but is rarely an issue on text or black-and-white scans. The advanced settings let you fine-tune DPI and JPEG quality independently of these three presets.

Why some PDFs barely shrink at all

A PDF that's already optimized (exported straight from office software, with few images or already-lightweight fonts) often has almost nothing left to lose: compression can't shrink what's already compact. A high-resolution scanned PDF, or one full of uncompressed screenshots or photos, can see its size cut by 5x or 10x, on the other hand. If a file barely moves, try the "Strong" level, or enable font subsetting and image deduplication in the advanced settings: those two, more than the compression level itself, often make the real difference on this kind of document.

Scanned PDFs vs. native PDFs: two different situations

A "native" PDF (exported from Word, a browser, or a layout tool) contains real vector text plus a handful of images: compression mainly acts on those images, and the text stays untouched. A "scanned" PDF, by contrast, is usually a sequence of full-page images, one per scanned sheet: there's no real text to preserve, only pixels. That's the kind of document where compression has the biggest impact, and where the DPI choice matters most: below roughly 150 DPI, scanned text starts becoming hard to read on screen, even though it usually still prints fine.

Going further with the advanced settings

Advanced settings can remove thumbnails, attachments, annotations, bookmarks, metadata or color profiles. Each option has different effects: removing annotations may remove visible elements, bookmarks help navigation, and color profiles can affect colors. Keep the original and check the result before sharing. Image deduplication and font subsetting are enabled by default; the size reduction depends on the document.

Frequently asked questions

Are my PDF files sent to a server?

No. All compression happens right in your browser: no file is ever sent to or stored on a server. You can verify this yourself: open your browser's developer tools (F12), Network tab, before compressing.

Is CocoonPDF really free?

Yes: no account, no limit on the number of files, and no watermark on the PDFs you produce. The site is funded by a small ad shown on the page.

Does compression cause visible quality loss?

It depends on the level you pick. "Light" and "Balanced" mainly adjust image resolution and JPEG compression, with a loss that's hard to spot with the naked eye; text stays sharp and selectable. "Strong" pushes further and can become visible on image-heavy documents: always compare before and after.

What's the maximum file size?

100 MB per file. Since everything runs in your browser, actual speed also depends on how much memory your device has available.

Can I compress several PDFs at once?

Yes. Drag and drop or select multiple files: they're processed one after another, and you can download them all at once when done.

Does it work on mobile?

Yes, right in the browser (Chrome, Safari...): no app to install.

Why did my PDF barely shrink?

Some PDFs are already optimized: few images, already-lightweight fonts, so there isn't much left to gain. A scanned PDF or one full of high-resolution images, on the other hand, can shrink several times over. Try the "Strong" level or turn on font subsetting in the advanced settings.

What information can the PDF lose during compression?

Depending on which advanced options you enable, CocoonPDF can strip metadata, attachments, annotations, the outline (bookmarks), or the color profile: handy before sharing a document publicly. These are off by default, except image deduplication and font subsetting.

How do I compress a PDF that's too large or too heavy?

Try the "Strong" level for maximum compression, or enable Deduplicate identical images and Subset embedded fonts in the advanced settings: these options specifically target the heaviest PDFs, which are usually loaded with images or unoptimized fonts.