macOS Preview has a built-in "Reduce File Size" option, but it is infamously aggressive — it destroys image quality with no control over the output. ModernPDF gives you the compression control Preview lacks, runs entirely in your browser, and never uploads your file.
Navigate to the Compress PDF tool. No installation, no app download. Works in any modern browser on macOS.
Drag the file from Finder directly into the browser window. The tool processes it locally — nothing is uploaded.
Select light, medium, or maximum compression. Download the result to your Mac. The original file is untouched.
ModernPDF uses WebAssembly to run compression algorithms directly in your browser. Safari, Chrome, and Firefox all support this natively on macOS.
Your PDF stays on your machine throughout the process. The file goes from Finder into the browser's local memory and back to your Downloads folder.
Unlike Preview's limited compression or paid apps like PDF Expert, ModernPDF requires zero installation and gives you control over compression strength.
Every Mac user eventually discovers the Quartz filter "Reduce File Size" in Preview. It works — files get smaller. But Preview offers no control over how much compression is applied. A 5MB PDF might drop to 200KB, but the images inside will look like they were faxed in 1998. There is no middle ground.
PDF Expert and Acrobat Pro offer better control but require paid installations. ModernPDF splits the difference: full control over compression strength, runs in any browser, free to start, and never uploads your file.
For Mac users who handle sensitive documents — legal contracts, medical records, financial statements — the zero-upload architecture means your files never leave your Mac, period. Not "deleted after an hour." Not "encrypted in transit." Never uploaded in the first place.
Preview's Quartz filter destroys image quality with zero control. If you have ever been frustrated by blurry images after Preview compression, this is your fix.
Adobe Acrobat is expensive and heavy. Mac users who need occasional compression should not have to install a 500MB app.
IT-managed Macs often restrict software installation. Browser-based compression works without admin rights.
Legal, medical, and financial professionals on Mac who need to compress documents without uploading them to any cloud service.
Preview (built-in): Free, but applies a single aggressive compression level with zero control. Images are dramatically degraded. Useful only when quality does not matter at all.
PDF Expert ($80 one-time): Offers compression with quality presets. Requires installation and storage. Good tool, but costs money and is Mac-only.
Adobe Acrobat Pro ($22.99/month): Full compression control with optimize-for-web options. Powerful but expensive, heavy (500MB+), and requires a subscription.
ModernPDF (free / $9/month Pro): Browser-based, three compression levels, zero installation. Files never leave your Mac. Works in Safari, Chrome, or Firefox. Free tier covers 3 compressions per day.
For occasional compression needs, ModernPDF is the practical choice — you get the control that Preview lacks without the cost and bloat of Acrobat.