Compress PDF
Light, honest optimization: object-stream recompression plus optional metadata stripping. Quality never reduced. Best for text/vector PDFs; image-heavy files need desktop tools.
How PDF Compression Works Here
Upload your PDF and choose a preset. Light re-saves the file with compressed object streams, the standard PDF mechanism for packing the document structure tighter. Balanced additionally strips metadata such as author name, creation app, and timestamps, which saves a little space and removes identifying info. Maximum goes further with structural flattening where pdf-lib allows it. The tool then shows exact before and after sizes plus the percentage saved, so you can decide whether to keep the result.
Honest Limits
A browser-based compressor has one hard limit: it cannot downsample or re-encode embedded images, and images dominate the size of scanned or photo-heavy PDFs. Expect 5 to 20 percent savings on text and vector documents, and near zero on image-heavy ones. The tool reports the real numbers instead of pretending. What it never does is reduce quality: pages are never re-rendered, so if the saving is small, the file is at least untouched. For dramatic shrinkage of image-heavy PDFs, a desktop tool with image re-encoding is the right choice.
Privacy
Everything runs locally with pdf-lib. Your document never uploads, and the Balanced and Maximum presets actually improve privacy by stripping metadata that can identify you or your software. Encrypted PDFs cannot be opened; remove the password in a desktop reader first.
Why Some PDFs Resist Compression
Open a stubborn PDF and look at what is inside. Scanned pages are full-page images, often saved without much compression, and they can account for 95 percent of the file size. No container-level optimization will shrink them because the bytes are already the images themselves. Your options then are: re-export from the original application at lower image quality, run scans through Grayscale PDF at standard quality (grayscale JPEGs are much smaller than color ones), or split the document into parts. Text-first PDFs, by contrast, compress beautifully, so the tool earns its keep on reports, manuals, and ebooks.
Frequently Asked Questions
How does this PDF compressor work?
Upload your PDF and pick a preset. The tool re-saves the document with pdf-lib using compressed object streams and, on the stronger preset, strips document metadata like author and creation software. This typically shrinks text-heavy PDFs by 5 to 20 percent. The interface shows before and after sizes so you can judge whether the saving is worth it. Everything runs in your browser.
Why did my PDF barely shrink?
Because of an honest technical limit: pdf-lib cannot downsample or recompress embedded images, and images are what make most PDFs large. If your file is mostly scanned pages or photos, recompression of the PDF container saves almost nothing. For big savings on image-heavy files you need a desktop tool that re-encodes images at lower quality, which browsers cannot do well. This tool is best for text and vector documents.
What is the difference between the presets?
"Light" re-saves with object-stream compression only, the safest option that changes nothing visible. "Balanced" adds metadata stripping (author, title, producer info), which saves a little more and also improves privacy. "Maximum" does both plus removes the document ID and flattens the structure as much as pdf-lib allows. None of the presets touch page content or image quality.
Will compression reduce the quality of my PDF?
No. This compressor never re-renders pages or recompresses images, so quality is preserved at 100 percent. If the tool cannot shrink your file meaningfully, it tells you so with the before/after numbers rather than degrading anything silently. That is the tradeoff of an honest browser-based compressor.
My PDF is still too big for email. What now?
First try the Maximum preset. If the file is image-heavy, the real fix is reducing image content: use PDF to JPG to check which pages are scans, or re-export the source document at lower image quality from its original app. As a last resort, split the PDF into smaller parts with the Split PDF tool and send them separately. Most email limits are 20-25 MB.
Is my file uploaded to a server?
Never. Compression runs entirely in your browser with pdf-lib. The file is read into memory, re-saved, and downloaded straight back to you. The tool works offline once the page has loaded. The tool works offline once the page has loaded.