Compress PDF Without Upload — Free & Private
Reduce PDF file size entirely in your browser. Your file never touches a server.
No Upload Ever
pdf-lib runs in your browser tab. Zero server transmission.
See Savings Before Downloading
Before/after size shown so you know exactly how much was saved.
Instant
No queue, no email. Download as soon as processing finishes.
The problem with online PDF compressors
Every major online PDF compressor — Smallpdf, iLovePDF, PDF2Go, Adobe Acrobat Online — works the same way: you upload your PDF to their server, their server processes it, and the result comes back to you.
For a photo album or a newsletter that is fine. But most people who need to compress a PDF are compressing it because it is large, and large PDFs tend to be large because they contain a lot of content — contracts, financial reports, medical records, legal filings. Exactly the kind of document you do not want on a stranger's server.
Our compressor solves this by running entirely in your browser tab using pdf-lib, an open-source JavaScript library. Your PDF is read into your device's memory, compressed, and written back out — without touching the internet.
How we compare
| Service | Files uploaded? | Free? |
|---|---|---|
| 365tools (this site) | Never | Always free |
| Smallpdf | Yes — to their servers | 2 tasks/hour free |
| iLovePDF | Yes — to their servers | Limited (size cap) |
| PDF2Go | Yes — to their servers | Limited |
Frequently asked questions
How does browser-based PDF compression work?
The tool uses pdf-lib to read your PDF's internal structure in memory, remove redundant objects and unused resources, and rewrite it as a smaller file — all inside your browser tab. No data is ever transmitted to a server.
How much compression can I expect?
Results depend on the PDF. Text-heavy PDFs with incremental edits can see 10–30% reduction. PDFs with redundant object streams may see more. The tool shows you the before and after size so you know exactly how much was saved.
Why not use Smallpdf or iLovePDF?
Both services upload your file to their servers to process it. If your PDF contains confidential information — contracts, financial records, medical documents — that file passes through infrastructure you don't control. Our tool never transmits your file.
Does this compress images inside the PDF?
The browser-based tool optimizes the PDF object structure but does not downsample embedded images (which requires re-rendering). For maximum compression on image-heavy PDFs, Ghostscript on the command line will give better results. See our guide on reducing PDF file size for all methods.
Is the compressed PDF identical in appearance?
Yes. The tool reorganizes the internal structure of the PDF without modifying the visual content. All fonts, images, and formatting remain exactly the same.