How to compress a PDF in your browser
- Open your PDF. Choose the file or drop it anywhere on the page. It is opened in your browser's memory and never sent to a server.
- Pick a preset. Each preset shows an estimated output size, computed from your actual first pages. The preview shows page one exactly as it will look.
- Compress and check. Watch the per-page progress, then compare the before and after sizes. If the output is not smaller, the tool says so.
- Download. Rename the output if you like and download it. Keep your original — the compressed copy has no selectable text.
What it does
- Three presets — Email, Balanced, High quality — each with an estimated output size before you commit
- Side-by-side preview of page one, before and after, so you judge the quality yourself
- Before/after size comparison with the percentage saved
- Warns you when compression would make the file larger, instead of pretending it helped
- Per-page progress for long documents
- Runs entirely on your device — nothing is uploaded
What this tool does
It makes a PDF smaller by re-rendering each page as a JPEG image at a resolution you choose, then rebuilding a fresh PDF from those images. A 40 MB phone scan typically lands between 2 and 6 MB on the Email preset. The engine is PDF.js — the same open-source renderer inside Firefox — plus pdf-lib for the rebuild, both running in your browser.
Why the no-upload part matters
Search for "compress PDF" and nearly every result is a website that takes your file first. That usually means your lease, tax return, or signed contract travels to a server you know nothing about, governed by a privacy policy you didn't read. This page does the same job without the trip: the code comes to you, your document stays put. It even works offline once the page has loaded.
Choosing a preset
Email (110 dpi) is for attachments that must fit under a mailbox limit — text stays readable on screen but fine print softens. Balanced (150 dpi) reads well on any screen and is the sensible default. High quality (200 dpi) keeps small text crisp at the cost of size. Every preset shows an estimate computed from your actual pages, and the preview pane shows page one exactly as it will come out — judge with your own eyes before committing.
The honest tradeoff
Compressed pages are pictures. You cannot select, search, or copy text in the output, and screen readers cannot read it. That is not a flaw of this tool specifically — it is how client-side PDF compression works. The tool states it next to the download button rather than in fine print, and it tells you outright when compression made your file larger, which genuinely happens with text-heavy PDFs that were already compact.
When you'd use it
Shrinking a scanned lease that bounced from someone's inbox. Emailing a phone-photographed receipt trail to an accountant. Getting an insurance claim's photo bundle under an upload limit. For keeping documents findable afterwards — that's what the Paperlock app is for: it reads your documents on your iPhone and answers questions about them.
How to compress a PDF on Mac
The quickest way to compress a PDF on Mac is Preview, which is already installed. Open the PDF, choose File → Export…, and in the export sheet set Quartz Filter to Reduce File Size, then save under a new name. That is the whole built-in option. There is no compress step in Finder's Quick Actions, and the Reduce File Size filter has no settings: it downsamples every image hard, so scans often come out blurry, and you cannot pick a gentler level or see the result before saving.
If that output is too rough, use the tool above instead. It runs in Safari or Chrome on your Mac with nothing to install, lets you pick Email, Balanced or High quality, and shows page one before and after so you judge with your own eyes. The before and after sizes are printed next to each other, and the file never leaves your Mac.
How to compress a PDF on iPhone
There is no built-in way to compress a PDF on iPhone. The Files app can preview, rename and share a PDF, but it has no shrink option, and Mail's offer to reduce the size of an attachment only applies to images — a PDF goes out at full size. The usual workaround is installing an app or uploading the file to a website, which is exactly what you may not want to do with a lease or a medical record.
This page works in Safari on iPhone with no app. Tap Choose a PDF, pick the file from Files or a recent download, choose a preset, and save the result back to Files or share it straight into Mail or Messages. The work happens in Safari's memory on the phone. A long scan takes a little longer on a phone than on a laptop — the per-page progress bar keeps counting, so give it a moment.
What does compress PDF mean — and can you get to 1MB, 200KB or 100KB?
To compress a PDF means to re-encode the parts of the file that take up space — almost always the page images — so they need fewer bytes. A page scanned at 300 dpi holds far more detail than a screen can show, so saving it at 110 or 150 dpi loses little you can see while cutting the size by a large factor. Text in a born-digital PDF is already tiny, which is why compressing a Word export rarely helps; this tool turns pages into images, so a text-only file can even grow, and the tool says so instead of pretending.
Whether you can compress a PDF to 1MB, 200KB or 100KB depends on what it is made of. A photographed or scanned document shrinks a lot: a 15 MB phone scan of a few pages usually lands under 1 MB on the Email preset, and a single scanned page can get near 200 KB. 100 KB is realistic only for one short page. The method is simple: pick Email, read the size estimate beside the preset, compare it with the limit, and if it is still over, split a long document into two files. The final size is always shown before you download.