MBOX viewer — open .mbox files online
Read a Gmail Google Takeout export or a Thunderbird / Apple Mail mailbox without installing a mail program. Search the messages, filter by Gmail label, read them safely and save them as .eml, ZIP or CSV.
Files without an extension (Thunderbird's "Inbox", Apple Mail's "mbox") work too. Large Takeout files are read in pieces.
| Date | From | Subject | Size |
|---|
Attachments
| Name | Type | Size |
|---|
All headers
What you can do
- Browse the mailbox — date, sender, subject and size of every message, 100 per page, newest or oldest first.
- Search — instantly by subject, sender and recipient; optionally inside the message bodies too.
- Filter by Gmail label — Takeout exports keep each message's labels (X-Gmail-Labels: Inbox, Sent, your own labels).
- Read a message — formatted HTML or plain text, embedded pictures, attachments to download, forwarded mails, all headers.
- Convert MBOX to EML — save one message as .eml, or the selected / filtered messages as a ZIP of .eml files.
- Export the list to CSV — date, from, to, subject, labels and size, UTF-8 with BOM so Excel shows every language correctly.
Where .mbox files come from
- Gmail: Google Takeout → select only Mail → the download contains Takeout/Mail/All mail Including Spam and Trash.mbox. Unzip it first.
- Thunderbird: each folder is an mbox file without extension in your profile's Mail or ImapMail folder (Inbox, Sent, …). The ImportExportTools NG add-on also exports .mbox.
- Apple Mail: Mailbox → Export Mailbox… creates a folder ending in .mbox; drop the file named mbox inside it.
Safe and private
The mailbox is read by JavaScript on your device; nothing is sent to a server. Large files are read piece by piece with only the headers kept for the list, so a multi-GB Takeout export does not have to fit in memory. E-mail HTML is shown in a sandboxed frame that cannot run scripts, and remote images are blocked, so opening old mail here does not ping any tracking pixels.
Questions
Do I need to unzip the Takeout download?
Yes. Google delivers a .zip or .tgz; extract it and choose the .mbox file inside. A ZIP itself cannot be opened here.
Why are fewer messages listed than I expected?
Messages are split at lines that begin with "From " followed by a sender and a date, as every mbox writer produces. If a mailbox was written by a tool that does not escape such lines inside messages, two messages may be merged or one split; the .eml export still contains every byte.
Some characters look wrong in the subject.
Encoded headers in UTF-8, ISO-2022-JP, Shift_JIS, EUC-KR, GB2312 and other charsets are decoded. A subject that was sent as raw 8-bit text in an undeclared legacy charset may still appear garbled.
Can I open Outlook .pst files?
No. .pst is Outlook's own database format. This viewer reads mbox; for single Outlook-exported mails use the EML viewer.
Is there a size limit?
Indexing works on files of many gigabytes. Exporting thousands of messages as one ZIP is built in the browser's memory, so for very large exports filter by label or date and export in parts.