A document received through WhatsApp or Telegram won't open — "Can't open file", a corrupt-file error in Word/Acrobat, or Telegram's "File download could not be completed"

What's actually wrong

WhatsApp and Telegram do NOT compress documents the way they compress photos, so a document that arrives is normally byte-identical to what was sent. When one won't open, it's almost always an incomplete download (connection dropped mid-transfer), a phone-side problem (no storage space, missing permissions, no app registered for that file type) — or the sender's original was already broken before they hit send. Work through those in that order before assuming corruption.

Free fixes — try these first

1. Delete and re-download. An interrupted download leaves a truncated file. Delete the local copy, get on stable Wi-Fi, and download again — or ask the sender to resend so you get a fresh copy.
2. Open it with the right app. Long-press the file → Open with (or share it to Files/Drive first) and pick Word, Excel, or a solid PDF reader. The in-app viewer fails on files that other apps open fine.
3. Free up space and clear the cache. A nearly-full phone silently breaks downloads: free a few GB, then clear the messaging app's cache (Android: Settings → Apps → WhatsApp/Telegram → Storage → Clear cache) and re-download.
4. Move it to a computer. Email the file to yourself or copy it over and open it in desktop Word/Excel/Acrobat — this rules out every phone-side cause in one step, and Open and Repair is available there.
5. Compare sizes with the sender. If your copy's size doesn't match the sender's, the transfer truncated it — resend. If the sizes match and it won't open on their device either, the original itself is damaged.

If the free fixes fail

If a fresh resend still won't open anywhere, the sender's original file is damaged and re-transfers can't fix that — our analyzer inspects the file's actual structure, spots mislabeled files (fixed free), and shows honestly how much of the document is recoverable.