You scanned a document with your phone’s camera — a form, a bank statement, a signed agreement — and the PDF that came out is enormous. Now you’re trying to email it or upload it somewhere, and it won’t go through. You don’t need a laptop and you don’t need to install a PDF app from the store. You can compress it right where you are, in the browser you already have open.
Compress PDF runs entirely in the phone’s browser using plain JavaScript, and it uses a real <input type="file"> element to pick your document — not a drag-and-drop box built for a mouse. That matters more than it sounds: plenty of browser-based PDF tools break on mobile because their upload zone assumes a desktop file explorer and a cursor. This one has been checked and confirmed working on mobile Safari and on Android Chrome, tapping through the actual native picker sheet on each.
Why the file is so big in the first place
A camera-scanned page isn’t really “a PDF” the way a Word export is — it’s a photo wearing a PDF wrapper. Scanning apps capture each page at whatever resolution the phone’s camera defaults to, which is almost always more detail than a screen or a portal upload will ever need, and every one of those full-resolution photos gets embedded in the document as its own image. Stack five or six pages at that resolution and the file balloons, while the same five pages exported straight from Word or Google Docs — text and vector lines, no photos — would stay small by comparison. That gap between “a photo of a page” and “text describing a page” is exactly what compression closes: it re-encodes each embedded image at a lower quality and, if needed, a lower resolution, since none of the extra detail a phone camera captured was ever doing anything for a document nobody’s going to zoom into past normal reading size.
On iPhone (Safari or Chrome)
- Open fatafatpdf.com/tools/compress-pdf in Safari or Chrome.
- Tap the upload area. iOS brings up its file-picker sheet with Browse and Recents tabs.
- Tap Browse for Files, iCloud Drive, or a connected Google Drive/Dropbox folder — or Photos if the scan is sitting in your camera roll.
- Pick the file. The first time, iOS asks permission to let the site access your photos or files — tap Allow.
- Type your target size in KB or MB if a form or portal gave you an exact number, or tap Low, Recommended, or Extreme.
- Tap Compress, then Download. Save to Files, or share it straight to Mail or Messages.
On Android (Chrome, Samsung Internet, or similar)
- Open fatafatpdf.com/tools/compress-pdf in Chrome.
- Tap the upload area. Android opens its own document picker, usually showing sources like Downloads, Drive, Photos, and any other storage app installed.
- Tap Downloads if the PDF came from an email or website, or switch to Photos/Gallery for a camera scan.
- Select the file and confirm, set your target size or compression level, same as above.
- Tap Compress, then Download. Android usually drops it into your Downloads folder, shareable from there.
The picker itself is the only real difference — iOS puts Browse and Recents in one sheet everywhere, Android’s picker varies a little by manufacturer. Once the file is selected, target size, Compress, and Download work identically on both.
Why target size beats a vague “quality” slider on a phone
Plenty of compression tools hand you a Low/Medium/High slider and leave you to guess whether the result fits whatever limit you’re dealing with. Re-running that guess over a slow mobile connection gets old fast. This tool takes the number directly — 200KB for NSP or CUET, 300KB for DU CSAS, 500KB for JOSAA, or anything you type — and works backward from it, adjusting quality and resolution until it lands. If the target genuinely can’t be hit without the text turning illegible, it says so instead of handing you a file that still gets rejected.
One tradeoff worth knowing: this tool rasterizes every page into an image regardless of which mode you use — a preset, or an exact target size. For a camera scan, that’s free — it was already a photo with no selectable text. For a PDF that started as typed text, you lose the ability to select or search it afterward, which rarely matters for a one-off upload or a quick email.
iOS already has a built-in compressor — here’s the gap it leaves
If you’re on an iPhone, you don’t strictly need a website for basic compression. Open the Files app, find the PDF, tap and hold it, and look for Optimize File Size under Quick Actions — it’s a genuine Apple feature, built in, free. On a scanned document it does a reasonable job of shrinking things.
The gap: it doesn’t take a target. You tap it, iOS optimizes by whatever amount its own logic decides, and you get back a smaller file with no say in how much smaller. If a portal wants your file at or under an exact number — 200KB, 300KB, whatever the form specifies — and the built-in optimizer lands you above it, there’s no second setting to try; that Quick Action doesn’t ask what number you’re aiming for. That’s the specific problem Compress PDF’s target-size mode solves — you type the number the form actually asked for, it searches for a quality and resolution that hits it, and it tells you plainly if that number genuinely can’t be reached. Android has no equivalent built-in feature at all, so this trick is iPhone-only.
If the picker doesn’t show your recent photos
This is almost always a permissions issue, not a problem with the tool. On iPhone, check Settings → Safari (or Settings → Chrome) for photo access — iOS sometimes defaults this to Limited or Off after an update. On Android, check Settings → Apps → Chrome → Permissions → Files and media and make sure it’s allowed, not restricted. If you denied the one-time prompt the first time you used the tool, this is where to fix it — then reload the page, since the picker doesn’t always refresh on its own. Also check you’re in the right source tab: a scan saved by a separate scanning app sometimes lands in that app’s own folder rather than Photos or Downloads.
Works on patchy mobile data too
Because the compression itself happens on your phone, not on a server, you only need a connection to load the page once. After that, selecting the file, compressing it, and downloading the result all happen locally — on a train, in a basement office, anywhere your signal drops to one bar. Nothing is uploading in the background to time out halfway through.
That’s also why it’s fine for anything sensitive — a signed contract, an ID scan, a medical form. The file never leaves your device, so there’s nothing to intercept en route and nothing sitting on someone else’s storage afterward.
FAQ
Do I need an app, or does this really work in just the browser? Just the browser. Nothing to install and nothing to open afterward — Safari or Chrome loads the page, the file picker and the compression both happen right there, and it stays a normal browser tab the whole time.
Is there a file size or page limit on mobile? No limit imposed by the tool — nothing uploads to a server that would need to enforce one. The real ceiling is your phone’s own memory. A typical scanned form or a handful of pages compresses in seconds; a very large, many-page PDF takes longer and leans harder on your phone’s memory than it would on a laptop, since phones generally have less to work with.
Do I need an internet connection the whole time? Only to load the page once. After that, picking the file, compressing it, and downloading the result all run locally in the browser tab — you can lose signal entirely partway through and it keeps working.
The page won’t open properly when I tap a link from WhatsApp or Instagram — what’s wrong? That’s usually an in-app browser problem, not the tool. Apps like WhatsApp, Instagram, and Gmail often open links in their own stripped-down browser view instead of Safari or Chrome, and that view can block the file picker from opening properly. Look for an “Open in Safari” or “Open in Chrome” option — usually behind a menu button in that in-app view — and use that instead.
How do I check the compressed file’s actual size afterward? Compress PDF already tells you on the result screen — it shows the new size next to the original, and if you set a target, it says plainly whether the result landed under that number or not. If you want to double-check on your phone directly: on iPhone, find the file in Files, tap and hold, and choose Info; on Android, long-press it in your Downloads or Files app and choose Details or Properties.
Next time a phone-camera scan is too big to send, open Compress PDF in whatever browser is already on your screen and get it down to the size you need — no app, no desktop required.