MBOX Viewer

How to use

1. 1Drop an .mbox file onto the upload zone, click Choose .mbox file to pick one from your device, or click Load sample to see the layout on a multi-message archive.
2. 2Read the Archive card for message count, attachment count, total size, and the date range of the messages inside.
3. 3Use the left rail to scroll the message list. Type in Search messages to filter by subject, from, to, or date. Click a row to open it.
4. 4In the right rail, switch between Body, Headers, and Raw source. In Body, choose Rendered, Plain text, or HTML source, and toggle Allow remote images on if you trust the sender.
5. 5Open Attachments to download any file (PDF, image, archive, calendar invite, CSV) from inside the message. Inline images referenced by cid are rewritten to local previews automatically.
6. 6Click Clear to drop the archive from memory and start over. The .mbox bytes are never uploaded.

About this tool

MBOX Viewer opens .mbox email archives in your browser and lets you browse every message inside without installing Thunderbird, Apple Mail, Outlook, or any desktop client. An .mbox file is the standard format used by Gmail Takeout (the export Google offers for your account data), by Thunderbird and SeaMonkey for every folder you keep, by Apple Mail for archived mailboxes, and by Postfix and Sendmail for system mailboxes. The viewer reads the archive locally with the FileReader API, splits it into individual messages at the standard 'From ' separator line, applies mboxrd unescaping for any '>From ' line that was quoted on the way in, and then parses each message as a normal RFC 5322 plus MIME email. Headers are unfolded and any RFC 2047 encoded-word values (subjects, names, and attachment filenames written in UTF-8, ISO-8859, Windows-1252, US-ASCII, in either Q or B encoding) are decoded so the message list and the message detail show readable Unicode. The MIME tree is walked at any nesting depth, multipart/alternative is resolved into the best text and HTML alternative for the message, multipart/related inline images referenced with cid: are rewritten to local Blob URLs so the rendered email looks correct without making any network request, and leaf parts in 7bit, 8bit, binary, quoted-printable, or base64 are decoded back to their original bytes. The left rail shows every message with subject, sender, date, and an attachment count; an instant search filters the list by subject, from, to, or date so a Gmail Takeout export with thousands of messages stays usable. The right rail shows the selected message with a rendered body inside a sandboxed iframe (sandbox="" so scripts and same-origin access are blocked; remote images are stripped by default and a counter shows how many tracking-pixel candidates were removed), a plain-text alternative, the original HTML source, all headers in a sortable table, and the raw RFC 5322 source. Attachments and inline parts are extracted as Blob URLs with the original filename and are offered as direct downloads, so you can rescue a PDF receipt, an iCal invite, or a CSV statement from an old archive in one click. The archive never leaves your tab: parsing, attachment extraction, and HTML rendering all happen on this device. Useful when a Gmail Takeout export drops a .mbox on your disk, when you migrate from one mail client to another and need to read the leftover archive, when a colleague hands you a Thunderbird folder for a postmortem, when you debug a delivery problem from an MTA mailbox, or when a security team needs to review a saved set of suspicious messages without opening them in a live mail client. Pair with the EML File Viewer when you only have a single .eml message rather than a multi-message archive, with the Email Header Analyzer to drill into delivery, SPF, and DKIM details, with the Email Validator and Email URL Extractor to audit addresses and links found inside a message, and with the Quoted-Printable and Base64 encoders if you want to inspect a transfer-encoded body by hand.

Free to use. Works in your browser. No signup, no login.