100% Private & Secure

Free MBOX Viewer
Browse Email Archives

Drop an .mbox file to browse all emails. Click an item to view. No upload — everything stays on your device.

View all emailsClick to read detailsThunderbird & Gmail compatibleHandles large files

Drop your .mbox file here

or click to browse

About

What Is an MBOX File?

MBOX is a standard format for storing many email messages in one file. Messages are concatenated and separated by a line that starts with the five characters "From " (the word "From" followed by a space). This convention comes from Unix mail systems and is still used by Mozilla Thunderbird, Apple Mail, and by Google when you export mail via Takeout.

An MBOX file is plain text: each email is in RFC 822–style format (headers plus body). Our free MBOX Viewer splits the file on the "From " separator, parses headers for each message, and shows you a list of all emails with From, Subject, and Date. Clicking an item displays its full headers and body — all private, with no upload.

Use the viewer to browse Thunderbird or Gmail exports on a machine without an email client, to verify an MBOX after migration, or to quickly find a specific message in a large mailbox. Your data stays on your device at all times.

Features

Features of the MBOX Viewer

Browse MBOX mailboxes with a clear list and detail view

Full Mailbox Browse

Parse MBOX by splitting on the standard 'From ' separator and list every email in a scrollable sidebar.

From, Subject, Date

Each list item shows sender, subject, and date so you can quickly find the message you need.

Detail Pane

Click an email to see its full headers and body in a clean, readable layout.

Email Count

Total number of emails in the MBOX is displayed so you know the size of the mailbox at a glance.

No Upload

Your MBOX file is never uploaded. Your data stays completely private.

Private & Secure

Your mailbox file never leaves your device. Ideal for personal or work archives.

How to use

How to View an MBOX File Online

Four simple steps — no install, no sign-up

01
01

Open the MBOX Viewer

Go to the MBOX Viewer page and you’ll see the upload area.

02
02

Drop Your .mbox File

Drag and drop an .mbox file (e.g. from Thunderbird or Gmail export), or click to browse.

03
03

Browse the Email List

All emails appear in the sidebar with From, Subject, and Date. Scroll to find the one you want.

04
04

Click to View Details

Click any email to see its full headers and body in the detail pane on the right.

Use cases

Use Cases for the MBOX Viewer

When and why to open MBOX files online

Thunderbird Export

Open MBOX files exported from Mozilla Thunderbird without installing the client.

Gmail Takeout

Browse MBOX mailboxes from Google Takeout to find specific messages or verify exports.

Migration Verification

Check that an exported MBOX contains the expected emails before migrating to another service.

Support & Legal

Inspect mailbox archives for support tickets or legal discovery without uploading them.

Quick Search

Use the list to quickly scan subjects and dates when you need to find one email in a large MBOX.

Development & QA

Verify MBOX output from scripts or apps during development and testing.

Compare Plans

Free vs Paid — MBOX Viewer

Get started free, upgrade when you need more power.

Feature
Free
Paid
Daily usage
5 uses/day
Unlimited
File size limit
10 MB
Up to 500 MB
All core features
No software installation
Works on any device
Files stay on your device
Batch processing
Priority support
Upgrade — starting at $6.99/mo
Upgrade to Full Version

Unlock the Full Power of MBOX Viewer

Remove daily limits, process larger files up to 500 MB, enable batch processing, and get priority support.

Buy Full Version — $6.99/moor $300 enterprise

File Viewers includes:

  • 21 file viewers included
  • Unlimited daily uses
  • 100 MB file size limit
  • All file formats supported
  • Email analysis tools

Also available in the All Tools Bundle

FAQ

Frequently Asked Questions

Common questions about the MBOX Viewer

Q1. What is an MBOX file?
MBOX is a common format for storing multiple email messages in a single file. Each message is separated by a line starting with 'From ' (with a space). Thunderbird, Apple Mail, and Gmail (via Takeout) can export mailboxes as MBOX.
Q2. Do you upload my MBOX file?
No. Your file is processed entirely on your own device and never leaves it. Nothing is sent to our servers.
Q3. Can I search within the MBOX?
The current viewer lists all emails and lets you scroll and click to read. Full-text search across the body could be added in a future update; for now you can use the sidebar to scan subjects and dates.
Q4. Why is the first message empty or wrong?
Some MBOX files have a leading 'From ' line before the first message; the parser splits on 'From ' so the first block might be a prologue. If you see odd behavior, it may be due to a non-standard or corrupted MBOX.
Q5. Does it work with Gmail MBOX?
Yes. MBOX files from Google Takeout use the same 'From ' separator. You can open them and browse all messages in the viewer.
Q6. Is the MBOX Viewer free?
Yes. The tool is free to use with no sign-up and no limits.
Q7. Can I export or download emails?
This viewer is read-only. It displays the contents of the MBOX but does not export or download individual messages. Use your email client or a dedicated converter for that.
Q8. What if my MBOX is very large?
Large files are loaded entirely into memory. Very big MBOX files (hundreds of MB) may cause slowdowns. For best performance, try with a smaller export or a single folder.
Related tools

Related Tools

More file viewers from OnlinePCTools

EML ViewervCard ViewerMSG ViewerPST ViewerMBOX Email CountAll Viewers