twineconvert

free · in-browser · no upload

MBOX to CSV
Converter

Drop your MBOX file. We'll convert it to CSV right here in your browser, your file never leaves your device.

or drop your file

Select your file here to get started

or drop your file here.

Accepts .mbox

nothing uploaded no file size cap no signup

How it works

Three steps. No upload, no signup.

  1. 1

    Drop your file

    Click the dropzone above or drag a MBOX from your desktop. Files of any size, there's no upload, so there's no upload limit.

  2. 2

    Convert in your browser

    The conversion runs entirely in this tab using JavaScript and WebAssembly. Your file never touches our servers, we don't have any.

  3. 3

    Download

    Get your CSV the moment the conversion finishes. Convert another, or close the tab.

Files stay on your device

Your file is never uploaded. The entire conversion runs in your browser using WebAssembly. We can't see what you convert because we have no server to see it.

No file size limit

Server converters cap free users at 1-2 GB and gate larger files behind a paid plan. Since nothing uploads, our limit is whatever your browser can handle.

Free, no signup, no ads on conversions

No account required. No watermark on the output. No queue. Drop a file, get a converted file.

Why convert MBOX → CSV

What this conversion is actually for

An mbox archive is one giant text blob of concatenated emails. Converting to CSV gives you one row per message with date, from, to, cc, subject, and message-id, which is exactly what you need to index a mailbox, build an e-discovery log, or analyze who emailed whom.

A real example

You exported your Gmail with Google Takeout and got a multi-gigabyte .mbox. You only need a list of who you emailed about an invoice. Convert to CSV, open in a spreadsheet, filter the subject column.

Troubleshooting

Bodies are not in the CSV.

By design. Message bodies vary wildly in size and would make the spreadsheet unusable. This tool indexes headers. Use mbox-to-eml or mbox-to-pdf if you need the full content.

Fewer rows than expected.

Unparseable or truncated messages are skipped rather than failing the whole file. If a large block is missing, the mbox may have been cut mid-message during export, re-export it.

Formats involved

About MBOX and CSV

MBOX, Unix mbox mailbox

MBOX is the Unix tradition for mailbox storage, a plain-text file containing many email messages back-to-back, separated by lines beginning with "From " (with trailing space). Used by Thunderbird, Apple Mail, Postfix, and as the export format from Gmail's Takeout service. Files for power users with years of mail can hit gigabytes.

How to open

Thunderbird (drop into a folder), Apple Mail (Import Mailboxes), Mozilla SeaMonkey, mutt. Convert to PDF for archival or single EMLs for individual message work.

Full MBOX format guide →
CSV, Comma-Separated Values

CSV is plain text, one row per line, fields separated by commas. The simplest possible tabular data format, which is exactly why it remains the most portable: every spreadsheet, database, programming language, and analytics tool reads CSV. Tradeoffs: no formulas, no formatting, no multiple sheets, and various edge cases around quoting fields that contain commas or newlines.

How to open

Excel, Google Sheets, Apple Numbers, LibreOffice Calc, any text editor, every database import wizard, every programming language with one line of code.

Full CSV format guide →

Related tools

Convert other files to CSV

Convert your MBOX to other formats

FAQ

Common questions

Is this MBOX → CSV converter really free?

Yes. No signup, no watermark, no daily file count limit. Every conversion runs in your browser, your file never touches our servers because there are no servers.

Where does my file go when I convert it?

Nowhere. The conversion runs entirely in your browser using JavaScript and WebAssembly. Your file is never uploaded to our servers. We don't have any servers handling files, there's nothing for us to log, store, or accidentally leak.

What's the maximum file size?

Whatever your browser can hold in memory. Practically, this means a few hundred MB on most computers, significantly larger than the 1-2 GB caps that server-upload converters charge for. Very large files (multi-GB) may require closing other browser tabs first.

Why convert MBOX to CSV?

Mass email archival; Gmail Takeout exports; long-term mail backups. Universal tabular data interchange. The most common reason to convert is compatibility, CSV works in places where MBOX doesn't, or vice versa.

How do I open a MBOX file in the first place?

Thunderbird (drop into a folder), Apple Mail (Import Mailboxes), Mozilla SeaMonkey, mutt. Convert to PDF for archival or single EMLs for individual message work.

Does this work offline?

Once the page is loaded, the conversion itself runs entirely offline. The first time you use a tool, your browser downloads the conversion library (a one-time cache). If you reload while offline, the page won't load, but you can install the site as a Progressive Web App for full offline use.

Can I convert multiple files at once?

Single file at a time for now. Batch conversion is on the roadmap, for now, drop one file, download the result, then convert the next.