01 / Fast steps
- Drop or select the .mbox file, whatever its size.
- The archive is scanned message by message without ever loading it whole.
- Download the index, the readable pages and the individual .eml files.
MBOX Viewer
You asked Google for your data and got a multi-gigabyte .mbox nothing can open. Drop it here: the archive is read a piece at a time so the size does not matter, you get an index of every message, a readable page for each, and each one back as a standalone .eml. Nothing is uploaded, which for a copy of your entire mailbox is the only sane arrangement.
drop your files anywhere in this area
Your files never leave your device. This tool even works offline.
MBOX
02 / Best for
- Read a Gmail Takeout export after closing an account, without setting up a mail client for it.
- Go through the mailbox of a deceased relative or of a closed company account.
- Recover a specific message from an archive Thunderbird refuses to open because of its size.
- Turn an archive into single .eml files that can be filed, searched or attached one by one.
03 / Why here
- Handles archives far larger than memory: the file is read in slices and each message is parsed as it is found, so a 20 GB export does not crash the tab.
- Produces an index of every message, with sender, date, subject and attachment count, as a CSV you can sort and search in a spreadsheet.
- Each message becomes a readable HTML page and a standalone .eml, so nothing stays trapped in the archive format.
- Scripts and remote images are stripped from the readable pages: opening a decade of archived newsletters cannot notify anybody.
- Runs offline once the page is loaded: an entire mailbox never reaches a server.
04 / Keep in mind
- A very large archive produces a lot of files, so a page limit applies to the readable pages while the CSV index always covers every message. The limit and what it left out are stated in the result.
- Attachments stay inside the exported .eml files rather than being unpacked separately: unpacking every attachment of a whole mailbox would produce thousands of files. Use EML Viewer on a single message to get its attachments.
- Encrypted or S/MIME-signed messages are shown as their signature envelope: this tool reads mail, it does not decrypt it.
Tool connections
Related tools
01EML ViewerOpen an EML email file without a mail client: read the message, see the headers and get the attachments back.02EML to PDFTurn an EML email into a dated PDF you can file, print or attach, without the message ever leaving your browser.03MSG to EMLOpen an Outlook MSG file without Outlook: read the message and get its attachments back.04CSV to ExcelConvert CSV files into Excel XLSX spreadsheets ready to open, sort and format.
Good to know
Questions & answers
01What is an MBOX file?
MBOX is the oldest and simplest way to store a mailbox: every message is written one after another in a single plain-text file, each one starting with a line that begins "From " followed by a sender and a date. That simplicity is why Google Takeout, Thunderbird and most Unix mail systems use it, and also why the files get enormous: a mailbox of ten years is one file of many gigabytes.
02Why can nothing on my computer open my Gmail Takeout file?
Because the format has no index. To show you a list, a program has to read the whole file, and most mail clients import it by loading it into memory or rebuilding their own database from it, which is slow and fails on very large files. Thunderbird in particular struggles past a couple of gigabytes. This viewer reads the file in slices instead, so the size stops being the problem.
03Is my mailbox uploaded to be read?
No, and here it matters more than anywhere else: an MBOX export is a copy of everything you have ever written and received. The file is read by JavaScript in your browser tab, slice by slice, and every output is written straight to your disk. It works with the network disconnected. No upload-based service should ever be trusted with a file like this.
04How do I find one specific email in a huge archive?
Use the CSV index the tool produces: it lists every message with its sender, date, subject and attachment count, which a spreadsheet can sort and filter in seconds. Once you know which message you want, its number tells you which exported page and .eml belong to it.
05Can I get a single message out as its own file?
Yes, that is one of the outputs: each message is exported as a standalone .eml, byte for byte as it appears in the archive, which any mail client can open and any archive can store. The escaped "From " lines that MBOX adds inside message bodies are unescaped on the way out, so the exported file is the original message rather than the archive copy of it.
06Is MBOX Viewer free?
Yes, completely free, with no sign-up and no file-size cap. It runs in your browser, so your mail never leaves your device.