🗜️ PDF Compressor
Shrink PDF file size with object-stream rebuilding, right in your browser. Ideal before emailing or uploading files with size limits. Free, unlimited, private — works entirely in your browser.
How to use
- Click the drop zone and select the PDF you want to shrink — or drag and drop it into the box.
- Confirm the file name and size shown below so you know you picked the right document.
- Click "Compress PDF" — the tool rebuilds your PDF with object streams, entirely in your browser.
- Your compressed file downloads automatically as compressed.pdf, and the tool tells you exactly how much space you saved in bytes and percent.
FAQ
Is it really free?
Yes — every tool on this site is 100% free with no limits, no signup and no watermarks.
Is my data private?
Absolutely. All processing happens locally in your browser. Your files are never uploaded to any server.
How much smaller will my PDF get?
It depends on the file. PDFs with bulky metadata, duplicated fonts or inefficient internal structure can shrink noticeably when rebuilt with object streams, while files that are already optimized may barely change. The tool shows your exact savings in bytes and percent — and if nothing could be saved, it tells you the file was already optimized instead of producing a pointless copy.
Will compression lower the quality of my PDF?
No. This compressor never downsamples images or alters visible content. It rebuilds the PDF's internal object structure using PDF object streams to strip out overhead, so your text, images and layout come out identical — only the file size changes.
Which PDFs compress best with this tool?
The best candidates are files exported from desktop software (Word, InDesign, reporting tools) that were never optimized, scanned-document PDFs carrying heavy metadata, and long multi-page reports. PDFs already saved with object streams by modern exporters may show little or no further savings.
Is it safe to compress the same PDF more than once?
Yes — running the tool on an already-optimized PDF is harmless. It simply returns a file of about the same size, so you cannot damage your document by trying.
How PDF Compression Works (and When to Use It)
Every PDF is a bundle of internal "objects" — pages, fonts, images, metadata entries — plus a cross-reference table that tells readers where each object lives. Many PDFs, especially ones exported from desktop software like Microsoft Word or Adobe InDesign, store these objects inefficiently: hundreds of tiny objects each carrying their own overhead, duplicated fonts, stale metadata and leftover editing history. The result is a file far larger than its visible content needs to be.
This tool fixes that waste without touching a single pixel. It loads your PDF in your browser using the open-source pdf-lib engine and saves it back with object streams enabled — a feature of the modern PDF specification that packs many small objects into compressed containers instead of storing them one by one. Nothing visible changes: text, images, hyperlinks and layout are preserved exactly. Only the structural overhead shrinks, which is why this kind of compression is completely lossless.
Best use cases
The most common reason to compress a PDF is a size limit you can't avoid. Email providers typically cap attachments around 25 MB; upload portals for job applications, university admissions, government forms and tax filings often cap at 5–10 MB. Shrinking a PDF is also useful before sharing over messaging apps with file-size limits, archiving large document collections on limited disk space, or loading heavy PDFs on a phone where every megabyte costs mobile data. Because this tool is lossless, it's safe for documents where quality matters — contracts, invoices, certificates and portfolios.
Tips for the best results
Compress before you merge: if you're combining several files with the PDF Merger, compressing each one first gives you the smallest final document. Keep your original until you've opened the compressed copy and confirmed it looks right — compression here is lossless, but keeping a backup is always good practice. If your PDF is mostly scanned images and the tool reports little savings, that's a different problem: the images themselves are the bulk of the file, and no structural rebuild can shrink them. And remember the tool needs an internet connection once, to load its PDF engine — after that, everything happens locally on your device, and your file never leaves your browser.
Common mistakes to avoid
Don't expect miracles on already-optimized PDFs — if a file was exported recently by a modern tool, it probably uses object streams already, and the compressor will honestly tell you so. Don't confuse this with quality-reducing "downsampling" compressors: this one never degrades your document, which is a feature, not a limitation. Finally, avoid compressing encrypted or password-protected PDFs, which the browser engine cannot open — remove the password in your PDF reader first, then compress.