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Uploaded file is empty or too large for the session

You might be here because: “The uploaded file is empty” · “This file is too large for this session” · “Uploaded file is too large. Max 64 MiB” · “can’t attach a file in the session” · “Couldn’t upload — the session isn’t reachable right now” · “file picker rejects my file” · “upload a photo in the session” · “attach a file”

Short answer

A file you send into a session travels to the session in one message, so each session has a per-file limit — often around 2.9 MiB, and never more than 64 MiB. An empty file is refused too. Use a smaller file (compress or resize it) and try again.

Check first

  • The drop zone names the limit for this session before you pick a file.
  • Is the session still running? Uploads need a live session (“This session is not running.”).

Likely causes and fixes

  1. Over the session’s limit. “This file is too large for this session (limit …).” — HTTP 413, nothing sent. Fix: shrink the file below the stated limit.

  2. Over the 64 MiB maximum. “[file name] is too large (max 64 MiB).” in the app; from code, HTTP 400 “Uploaded file is too large. Max 64 MiB.”.

  3. Empty file. HTTP 400 “The uploaded file is empty.”. Pick a file that has content.

  4. Session not reachable. “Couldn’t upload — the session isn’t reachable right now.” or “This session cannot be reached right now. Try again shortly.”. Wait and retry; if the session ended, launch again.

  5. From code: the session read’s upload_max_file_bytes gives the exact per-session figure; per-account and per-session totals are also capped.

  6. The upload worked, but the page didn’t get the file. To upload a file to a page: add it in Files first, then tap the page’s upload button. The page gets the newest unused file added on the same web address (www.example.com and example.com count as different), once, so add the file while that page is open; a second tap on a single-file input gets the next-older unused file, and when none is left, add the file again. Files you add are for this session only and are deleted when the session ends.

If it still fails

Press Talk to a person in this chat (or open Help) and include the file size, the limit shown and the session id. Limits are fixed per device and cannot be raised per account.