Describe the bug
Uploading a file larger than ~2 GB in Thunderbird Send fails. Smaller files upload fine, but past roughly 2 GB the upload errors out and the file is never sent. The failure happens early, while the progress banner still shows "Hashing…" (see #980).
To Reproduce
Steps to reproduce the behavior:
- Open Thunderbird Send (Firefox) and sign in.
- Upload files of increasing size.
- Observe:
- ~1 GB file: succeeds.
- ~2 GB file: fails with
Bug: can't construct the Blob.
- ~3 GB and ~4 GB files: fail with
Upload error for file 1: NotReadableError: The requested file could not be read, typically due to permission problems that have occurred after a reference to a file was acquired.
Expected behavior
Large files (Send advertises support well beyond 2 GB) should upload successfully, or at minimum fail with a clear, actionable message rather than a low-level Blob/read error.
Actual behavior
- ~2 GB:
can't construct the Blob
- ~3 GB / ~4 GB:
NotReadableError: The requested file could not be read, typically due to permission problems that have occurred after a reference to a file was acquired.
The failure appears to be tied to a ~2 GiB (2^31 bytes) boundary and occurs during the pre-upload hashing phase, before any bytes are uploaded.
Screenshots
System
- OS: Windows 11 25H2
- Browser Version: Firefox 152.0.5 (64-bit)
(A second reporter saw the same class of failure — 1 GB succeeded; 3 GB and 4 GB failed with the NotReadableError above.)
Additional context
Appears to be a client-side memory/File-API limitation: the pre-upload path reads whole slices into memory rather than streaming, so files crossing the ~2 GiB boundary hit browser Blob/ArrayBuffer/file-read limits. Related to the "Hashing…" phase tracked in #980.
Describe the bug
Uploading a file larger than ~2 GB in Thunderbird Send fails. Smaller files upload fine, but past roughly 2 GB the upload errors out and the file is never sent. The failure happens early, while the progress banner still shows "Hashing…" (see #980).
To Reproduce
Steps to reproduce the behavior:
Bug: can't construct the Blob.Upload error for file 1: NotReadableError: The requested file could not be read, typically due to permission problems that have occurred after a reference to a file was acquired.Expected behavior
Large files (Send advertises support well beyond 2 GB) should upload successfully, or at minimum fail with a clear, actionable message rather than a low-level Blob/read error.
Actual behavior
can't construct the BlobNotReadableError: The requested file could not be read, typically due to permission problems that have occurred after a reference to a file was acquired.The failure appears to be tied to a ~2 GiB (2^31 bytes) boundary and occurs during the pre-upload hashing phase, before any bytes are uploaded.
Screenshots
System
(A second reporter saw the same class of failure — 1 GB succeeded; 3 GB and 4 GB failed with the NotReadableError above.)
Additional context
Appears to be a client-side memory/File-API limitation: the pre-upload path reads whole slices into memory rather than streaming, so files crossing the ~2 GiB boundary hit browser Blob/ArrayBuffer/file-read limits. Related to the "Hashing…" phase tracked in #980.