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By PDFWix Editorial Team · May 2026
Compress PDF for WhatsApp — WhatsApp caps attachments at 100MB. Fastest free way to shrink a large scanned PDF for WhatsApp, works on any phone or laptop.
WhatsApp's hard cap on document attachments is 100MB across iOS, Android and WhatsApp Web. If your PDF is larger, you'll see 'File too large' the moment you try to attach it — there's no warning before that, and no Premium tier to pay for a higher cap.
The 100MB limit is generous compared to Gmail (25MB) or Outlook (20MB), but scanned documents can blow past it surprisingly fast. A 50-page colour scan at 300 DPI easily hits 200–400MB. If you care about preserving image fidelity while you shrink, walk through how to compress a PDF without losing quality first. If you're dealing with a much stricter portal — such as a government upload capped at 100KB or a visa form capped at 200KB — see our guides on compressing PDF to…
Almost every oversized scanned PDF is bloated by one of two things: scans saved at unnecessarily high DPI (600 DPI when 150 is fine for screen reading), or full-colour scans of black-and-white documents. The second one is the silent killer — a colour scan of a printed page is roughly 8x larger than the equivalent greyscale scan.
Open Compress PDF in any browser — works in mobile Safari, Chrome on Android, and on the laptop next to you. Drop the PDF onto the dropzone, pick the Strong compression preset, and click Compress.
For typical scanned documents, expect a 50MB original to drop to 3–8MB. That's well under the 100MB WhatsApp cap with margin to spare for very large originals.
If you're on iPhone and scanned with the Notes app, the resulting PDF is usually already compressed reasonably well — you may only need the Recommended preset, not Strong.
If you're on Android and used Google Drive's scanner, the output is often higher-DPI than necessary. Strong compression typically halves it without visible quality loss.
WhatsApp's hard cap is 100 MB for any single document attachment — PDF, DOCX, ZIP, anything. The limit is identical on iOS, Android, WhatsApp Web and WhatsApp Desktop, and there is no Premium tier that raises it. Files larger than 100 MB are rejected silently with a 'File too large' toast that gives no preview of how far over the limit you are.
There is a softer practical limit too. WhatsApp generates a thumbnail preview inline in the chat for documents under roughly 20 MB; bigger files send fine but show a generic file icon, which makes them feel less trustworthy to the recipient. If the preview matters (a CV, a portfolio, an invoice), aim for under 20 MB even though the hard limit is 100 MB.
Open Safari on your iPhone and go to Compress PDF. Tap the dropzone, choose 'Files', and pick the PDF from iCloud Drive, Notes scans or the Files app. Select the Strong preset and tap Compress — processing happens locally in mobile Safari via WebAssembly, so even a 50 MB scan finishes in 20–40 seconds on a recent iPhone.
Tap Download to save the compressed PDF back to Files. Then open WhatsApp, tap the attachment icon in the chat, choose Document, navigate to the compressed file and send. The whole flow stays inside your phone — no app install, no upload to a server, no signup.
Open Chrome on Android and go to /compress-pdf. Tap the dropzone, pick the file from Downloads, Drive or wherever you stored it, choose Strong and tap Compress. Save the result to your phone. In WhatsApp, tap the paperclip icon, choose Document, pick the file from your file manager and send.
Tip: if the PDF came from Google Drive's Scan feature, it's almost always over-DPI'd for what WhatsApp needs. Strong compression typically halves a 30 MB scan to 12–15 MB with no visible quality loss on a phone screen. For really large originals (200 MB+ legal documents), compress twice — the second pass usually shaves another 10 percent without artifacts.
WhatsApp's hard limit is 100MB. Use Compress PDF Strong preset — most scanned documents drop to under 10MB.
No — unlike images, WhatsApp does not re-compress document attachments. The recipient gets the exact file you sent.
Yes. Open Compress PDF in mobile Safari, pick the file from Files or iCloud, compress, save back to Files, then attach in WhatsApp.