MBOX File Viewer - Open MBOX Files Online

Open MBOX mailboxes from Gmail Takeout, Thunderbird or Apple Mail right in your browser - even multi-GB files, with nothing uploaded. Search, sort and read every email, then export them as .eml or CSV. Single emails open in the EML & MSG Viewer, Outlook mailboxes in the PST Viewer.

Try a sample
No upload Multi-GB files Gmail labels EML & CSV export
Related Tools
EML & MSG Viewer PST Viewer CSV Viewer VCF Viewer ZIP Viewer

How to open an MBOX file online

  1. Open your mailbox. Drop an .mbox file anywhere on the page or browse for it. Gmail Takeout .zip files and .mbox.gz files work too, and so does the sample mailbox.
  2. Browse and search. Sort by date, sender, subject or size, filter by label, group conversations, and search with operators like from:, subject: or has:attachment.
  3. Read any email. Click a message to read it with its formatting, pictures and attachments, check its headers, or print it to PDF.
  4. Export what you need. Select messages and export them as .eml files (a ZIP for more than two), or save the list as CSV or JSON.

Keyboard shortcuts in the message list

  • Next / previous email↓ / ↑ or J / K
  • Select the emailSpace or X
  • Select a rangeShift + click
  • First / last emailHome / End
  • Jump to the list from search↓
  • Clear the searchEsc

MBOX viewer features

Built for big mailboxes

A background worker reads the file in 32 MB slices and the list only draws what is on screen, so 100,000 emails scroll smoothly.

Takeout ZIP and .gz

Drop the Google Takeout ZIP as it is, or a gzip-compressed mailbox - it is unpacked in your browser.

Search like Gmail

from:, to:, subject:, label:, has:attachment, before: and after:, plus full-text search inside every email.

Labels and conversations

Gmail labels become one-click filters, and replies can be grouped into their conversations.

A real email reader

Formatting, inline pictures, attachments with preview, headers with SPF / DKIM / DMARC, print to PDF.

Safe and private

Nothing is uploaded, scripts in emails never run and remote images stay blocked until you allow them.

MBOX to EML

Export any selection as standard .eml files - one ZIP with a README for more than two emails.

CSV and JSON lists

Dates, senders, recipients, subjects, sizes and labels for spreadsheets, audits or scripts.

What is an MBOX file?

An MBOX file is a whole mail folder saved as one long text file.

Each email is stored one after the other, and every message starts with a separator line that begins with "From ".

The format dates back to early Unix mail systems and is still used today. Thunderbird keeps its folders in this format, Apple Mail exports mailboxes as .mbox, and Google Takeout delivers your Gmail as one big .mbox file.

MBOX variants this viewer reads

  • mboxo and mboxrd - the classic forms. Lines inside an email that start with "From " are saved as ">From "; the viewer puts them back.
  • Thunderbird - separator lines like "From - Sat Mar 16 10:00:00 2024", often with Windows (CRLF) line endings.
  • Gmail Takeout - one file for all mail, with X-Gmail-Labels and conversation IDs that become filters here.
  • Apple Mail - an export folder ending in .mbox with a file called "mbox" inside.

MBOX vs PST vs EML

FormatHoldsUsed byOpen it with
.mboxMany emails in one text fileGmail Takeout, Thunderbird, Apple MailThis viewer, Thunderbird
.pst / .ostA whole Outlook mailbox with folders, calendar and contactsMicrosoft OutlookPST Viewer, Outlook
.emlOne emailEvery mail appEML & MSG Viewer
.msgOne Outlook itemMicrosoft OutlookEML & MSG Viewer

Open your Gmail Takeout MBOX

Google Takeout is how you download a copy of your Gmail.

  1. Go to takeout.google.com, click Deselect all, then tick Mail.
  2. Choose Next step, keep the ZIP format and create the export. Google emails you when it is ready.
  3. Download the ZIP and drop it here as it is - or unzip it and drop the .mbox file from the Mail folder.

Your labels show up as filters above the list. Large accounts are split across several ZIP files; the mailbox is in the one that contains the Mail folder.

How to open MBOX files on Windows, Mac and phones

This viewer works the same everywhere: open the page, pick the file, done.

If you want the mailbox inside a desktop mail app instead, these are the usual routes:

Windows

Outlook cannot import MBOX files. Mozilla Thunderbird can, with the free ImportExportTools NG add-on (Import mbox file). For a quick look, or to pull out a few emails as .eml, this viewer is faster.

Mac

Apple Mail imports MBOX files under File - Import Mailboxes. The emails then appear in a new "Import" folder.

iPhone, iPad and Android

Phones have no app for MBOX files. Open this page in Safari or Chrome, tap the drop area and pick the file from Files, Downloads or Drive.

Convert MBOX to EML, CSV or PDF

All exports run in your browser and work on the current filter or on your selection.

  • MBOX to EML - Export .eml gives you standard email files that open in any mail app or in the EML & MSG Viewer.
  • MBOX to CSV - one row per email for Excel or Google Sheets; check it in the CSV Viewer or the Excel Viewer.
  • Email to PDF - open a message and press Print / PDF. Combine several with Merge PDF.
  • Attachments - open the email and save one file, or all of them as a ZIP.

Why won't my MBOX file open?

  • "No messages" - the file is not an MBOX mailbox, or it is an Apple Mail export folder; drop the "mbox" file inside it.
  • It is a .pst file - that is Outlook's format; use the PST Viewer.
  • The download stopped early - the last emails will be missing or cut off. Download the export again.
  • A password-protected ZIP - unpack it with your password first, then drop the .mbox file.
  • Odd characters in old emails - legacy character sets (Cyrillic, Japanese, Central European) are decoded automatically.
  • The tab runs out of memory - exporting very large selections as one ZIP needs RAM; export in parts of up to about 1 GB.

Looking for another format? See all file viewers.

Frequently Asked Questions

Drop the .mbox file onto this page or click the drop area to browse. The viewer lists every message with sender, subject, date and size, and opens any email with its formatting and attachments.

Nothing is installed and nothing is uploaded.

Yes. Drop the .mbox file, or the Takeout .zip as it is - the viewer finds the mailbox inside and unpacks it in your browser.

Gmail labels such as Inbox, Sent, Starred or your own labels appear as filters, and conversations can be grouped.

Several gigabytes. The file is read in slices by a background worker and only an index of the messages is kept in memory, so the page stays responsive.

The limit is your device's memory for the index, which is small - about 350 MB of RAM per million messages.

Select the messages you want (or use the select-all box after filtering) and press Export .eml. One or two messages download as .eml files, more come in a ZIP with one .eml file per email.

Every .eml opens in Outlook, Thunderbird, Apple Mail and our EML & MSG Viewer.

Press Export CSV. You get one row per email with date, sender name and address, recipients, subject, attachment count, size, labels and Message-ID, in UTF-8 that Excel and Google Sheets open correctly.

Filter or select first to export only part of the mailbox. Check the file in the CSV Viewer.

Yes. The search box looks at senders, recipients, subjects and labels as you type, and understands from:, to:, subject:, label:, has:attachment, before: and after:.

Turn on the message text button to search the body of every email as well.

The file is probably not an MBOX mailbox, or it is empty. Apple Mail exports a folder ending in .mbox - drop the file called mbox inside it, or the whole folder.

Outlook .pst files need the PST Viewer, and single .eml or .msg emails the EML & MSG Viewer.

No. The MBOX file is read by your own browser and never leaves your device.

Emails are shown in a locked frame where scripts cannot run, and remote images stay blocked until you allow them, so nobody learns that you opened an old message.

Guides & Tutorials

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