New in the kilnmsg viewerics viewerqbo → csvbank → qbo
MBOX Viewer
Open an .mbox mailbox file — Gmail Takeout included — right in your browser. Browse messages, read bodies, save attachments. The archive never leaves your machine.
Private by construction. Your archive is opened with JavaScript inside this page. It is never transmitted, remote tracking images are blocked, and the tool keeps working with the network unplugged.
Google Takeout hands you your Gmail as an .mbox file, and then leaves you alone with it: no Google tool opens it, and the standard advice is "install Thunderbird and import your entire mail history into it," which is a lot of ceremony to read some emails. The other advice — an upload-based mbox viewer — is worse, because a mail archive is the single most private file you own. This page is the quiet third option: mbox is just messages concatenated with From separator lines, so the viewer indexes those boundaries in your browser, lists every message, and decodes one only when you click it.
The reader is the same engine as our MSG / EML viewer: multipart bodies, encoded subjects, quoted-printable and base64, attachments downloadable from memory, HTML rendered in a sandboxed frame with scripts stripped and remote tracking images blocked. Browsing stays fast in big boxes because nothing is decoded until you ask.
Questions this tool gets asked
How do I open an .mbox file without Thunderbird?
Drop it on this page. The mbox format is a plain concatenation of email messages, and this viewer indexes it in your browser - a message list with sender, subject, and date, and a full reader for each message including attachments. No mail client, no import, no upload.
Can it open a Gmail Takeout export?
Yes - Google Takeout delivers your Gmail as .mbox, and that is exactly what this page reads. A whole mail archive is about as private as files get, so the fact that it never leaves your machine is the point.
Is my mail archive uploaded?
No - never. The file is indexed and read entirely by JavaScript in your tab. There is no upload endpoint on this site. Load the page, go offline, and it still works.
How large a file can it handle?
The whole file is held in your browser's memory, so a few hundred megabytes is comfortable on a normal machine; multi-gigabyte archives depend on your RAM. Messages are only decoded when you open them, which keeps browsing fast even in big boxes. If your archive is too big, split it by year in Takeout.
Are remote images and scripts blocked?
Yes - message bodies render in a sandboxed frame with scripts stripped and remote images blocked, so newsletter tracking pixels stay dead. Images embedded in the message itself are shown.
Can't I just open an mbox file in a text editor?
Technically yes - mbox is a 1970s plain-text format, messages stacked end to end with From separator lines. Practically no: a Takeout export is thousands of messages with base64-encoded bodies and attachments inlined as text walls, and editors choke on the file size. This viewer reads the same plain text, but with an index, decoding, and a message list - and Thunderbird's known slowdown on multi-gigabyte imports never enters the picture.
Related tools
- msg / eml viewerOpen a single Outlook or exported email - same engine, one message.
- ics viewerOpen calendar files - events, attendees, locations - and export CSV.
- vcf → csvContacts out of vCard files and into a spreadsheet, locally.
- base64 ⇄ textEncode and decode base64 locally - handy for raw email parts.