In-memory processing
Compress PDF runs as JavaScript inside this tab.
Never uploaded
Safe for financials, contracts and NDAs.
No caps or sign-ups
File size is limited only by device memory.
Compress a PDF to get under email attachment limits or upload caps. The tool downscales and recompresses embedded images, which make up most of the size of scanned and image-heavy PDFs.
Also known as Reduce PDF size.
Compression works on embedded images. A PDF that is mostly text and vector graphics is already compact, so there is little to remove. Scanned documents and photo-heavy files shrink the most.
Yes. Compress PDF runs entirely inside your web browser using JavaScript, so the file never leaves your device. It is safe for confidential documents such as contracts, financial records and IDs.
There is no fixed limit, because the file is processed on your own device. Very large files depend on your device's available memory; a modern laptop or phone handles hundreds of megabytes.
Yes. ZapConvert runs in any modern browser, including Safari on iPhone and iPad and Chrome on Android, with nothing to install. You can add several files at once and download them together as a ZIP.