Compress PDF Online Free — Reduce PDF File Size
Free online PDF compressor: reduce PDF file size for email or upload limits. Three compression levels, runs 100% in your browser — no upload.
About PDF Compressor
Make a PDF small enough to email or upload. Pick a compression level and each page is re-encoded as an optimized image at a lower resolution — the technique that works best for the most common case: image-heavy PDFs like scans and exports. Everything runs in your browser, so the document never leaves your device.
How to use PDF Compressor
- Drop one or more PDF files into the upload area.
- Choose a compression level (Balanced is the right choice for most files).
- Download each compressed PDF and check the size reduction.
How PDF compression works (and when it helps)
What this tool actually does
Each page of your PDF is rendered and re-encoded as a JPEG at the resolution you choose, then the pages are reassembled into a new PDF. The result looks the same on screen, but takes far less space when the original pages contain photos, scans, or screenshots.
- Smallest file — 100 DPI, stronger compression. Great for emailing scans.
- Balanced — 150 DPI. The sweet spot for most documents.
- High quality — 200 DPI. When every detail matters and you only need a modest reduction.
When compression helps most — and when it can't
PDFs are big because of what's inside them. Scanned documents, photo-heavy reports, and slide exports shrink dramatically. A pure text PDF, on the other hand, is already tiny: its pages are just characters and vectors, and re-encoding them as images can even make the file slightly larger. If that happens, the tool tells you.
A good workflow: try Balanced first, and only move to Smallest if you still need to get under a size limit.
Typical size limits people compress for
| Destination | Typical attachment limit |
|---|---|
| Gmail / Outlook webmail | 25 MB |
| Most government e-filing portals | 1–10 MB |
| Job application portals | 2–5 MB |
| WhatsApp / messaging apps | 100 MB (but small sends faster) |
Why compress in the browser?
Online PDF compressors usually ask you to upload your document to their servers — and PDFs often contain exactly the kind of information you'd rather not hand to a stranger. This tool does all the work locally with pdf.js and pdf-lib compiled for the browser: no upload, no account, no watermark, no limit.
Frequently asked questions
Is this PDF compressor really free?
Yes — free with no account, no watermark, and no limit on file size or number of files.
Will the quality be noticeably worse?
At the Balanced level, pages are rendered at 150 DPI — sharper than most screens and more than enough for printing at normal reading sizes. Use High quality if you need to preserve fine detail.
My file didn't get smaller — why?
Your PDF is probably mostly text and vector graphics, which are already compact. This compressor re-encodes pages as images, which helps most with scans and image-heavy documents.
Does the output still have selectable text?
No — because pages become images, text in the compressed PDF can't be selected. If you need searchable text, keep the original or run our OCR tool on the compressed result.
Are my files uploaded to a server?
No. All processing happens locally in your browser using WebAssembly and Web APIs. Your files never leave your computer — close the tab and nothing remains.
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