# MBOX Viewer (ReadMBOX) > A browser-based MBOX file viewer and converter at https://readmbox.com/. Opens .mbox files from Google Takeout, Thunderbird and Apple Mail directly in the browser, with search, date and sender filtering, attachment extraction, and conversion to CSV (for Excel and Google Sheets), PDF, EML and smaller MBOX files. The mailbox is parsed entirely client-side and is never uploaded to any server. Reading and searching are free; a one-time $29 unlock adds bulk export. MBOX Viewer runs at https://readmbox.com/ and is built by One Scales Inc. Video tutorials are on the YouTube channel https://www.youtube.com/@readmbox. ## What it does - Opens .mbox files of any size — tens of gigabytes — by streaming the file in small chunks rather than loading it into memory. - Reads Google Takeout Gmail exports, Thunderbird mail stores and Apple Mail mailboxes. - Full-text search across messages, plus filtering by sender, recipient, subject, date range and whether a message has attachments. - Optionally groups replies into conversations, threading on the Message-ID, In-Reply-To and References headers, so a reply whose subject was changed still sits with the thread it belongs to. - Views and downloads individual attachments, or bulk-extracts every attachment across thousands of messages into a single ZIP, optionally filtered to images, PDFs or documents. - Converts to CSV (opens directly in Excel, Numbers and Google Sheets), a PDF archive, original .eml files, or a smaller .mbox. - Exports an addresses-only CSV: one row per email address, with how many messages that address sent and how many were sent to it. - Every export can cover a single message, the current filtered view, or the whole mailbox. - Requires no install, no browser extension and no account. Once the page has loaded it works with the internet connection turned off. - Works in desktop Chrome and Edge on Windows, Mac, Linux and ChromeOS. Mobile browsers cannot handle files of this size. ## Convert MBOX to other formats All conversions run in the browser on your own computer. The steps are the same each time: open the .mbox file at https://readmbox.com/, filter down to the messages you want (optional), click Export, choose what to export (this message, current view, or whole mailbox) and pick a format. ### MBOX to CSV, Excel and Google Sheets - Output: one CSV file, one row per message. - Columns: date, from, to, subject, size_bytes, attachments, and optionally body (the plain-text message body, capped at 32,000 characters per message). - The file is UTF-8 with a byte-order mark, so Excel shows accented and non-Latin characters correctly when you double-click it. - There is no native .xlsx export. The CSV opens directly in Excel; save it as .xlsx from Excel if you need that format. In Google Sheets use File → Import → Upload. - Leave "include message text" off for a fast, small file with headers only; turn it on to get the message bodies. - Video: https://www.youtube.com/watch?v=kTDyo83cEf8 ### MBOX to an email address list (CSV) - Output: one CSV with one row per unique email address, plus a "from" count (messages that address sent) and a "to" count (messages where it was a To: recipient). - Addresses are lowercased so each address appears once. Cc and Bcc are not counted. - Useful for building a contact list from a Gmail backup, or seeing who a mailbox actually corresponds with. - Video: https://www.youtube.com/watch?v=gV_h79jOjhA ### MBOX to PDF - Output: a letter-size PDF archive. A cover sheet lists the source file name, message count and generation date; each message then starts on its own page with its headers and text, and pages are numbered. - Up to 500 messages per PDF. For larger mailboxes, filter by date range or sender and export in batches. - Suited to legal, records-retention, DSAR and eDiscovery work where a readable, printable record is needed. - Video: https://www.youtube.com/watch?v=kTDyo83cEf8 ### MBOX to EML - Output: a ZIP of .eml files, one per message, named after the subject. - Each .eml is a byte-exact copy of the original message, with all headers and attachments intact. - .eml files open in Outlook, Apple Mail, Thunderbird and Windows Mail, and can be dragged into those apps. ### MBOX to a smaller MBOX (split or filter a mailbox) - Output: a new .mbox containing only the messages matching the current filter, copied byte for byte. - Use it to split a huge Google Takeout file by year, sender or label, or to hand over just the relevant messages. Requires a filter to be applied. ### Extract all attachments from an MBOX - Output: one ZIP containing every attachment from the selected messages, optionally limited to images, PDFs, or documents and spreadsheets. - Combined with Google Takeout, this downloads every attachment in a Gmail account at once. - Video: https://www.youtube.com/watch?v=NrCZk3-NfV4 ### MBOX to Outlook (PST) - There is no PST export. To get MBOX mail into Outlook, export to EML and drag the .eml files into an Outlook folder. ## How to's ### How do I back up all my Gmail with Google Takeout? Go to https://takeout.google.com, click "Deselect all", then tick only Mail. You can include all mail or choose specific labels. Set the export size to 50 GB so Google produces one file instead of many, and create the export. Google emails a download link when it is ready (minutes to days, depending on mailbox size). Download and unzip it; the mail is a single .mbox file inside the Takeout/Mail folder. Open it at https://readmbox.com/ to read, search and export it. Video: https://www.youtube.com/watch?v=9W7tzmwou7o ### How do I open and read an MBOX file? Three ways. (1) In the browser at https://readmbox.com/: drop the file onto the page; nothing is uploaded and nothing is installed, and it works offline. (2) Thunderbird (Windows, Mac, Linux): skip the account setup, open Local Folders → Settings to find the message storage folder, copy the .mbox file there, and restart Thunderbird. (3) Apple Mail (Mac): File → Import Mailboxes and choose the .mbox file. Video: https://www.youtube.com/watch?v=ACbXU3-YlJY ### What is an MBOX file? A single plain-text file that holds many email messages, including their attachments, one after another. It is the format Google Takeout uses for Gmail exports and that Thunderbird and Apple Mail use to store and export mailboxes. Windows and most apps cannot open it by double-clicking, which is why a viewer is needed. Video: https://www.youtube.com/watch?v=dvnQG92N51E ### How do I convert MBOX to Excel, Google Sheets, PDF or EML? Open the file at https://readmbox.com/, filter by date, sender or attachments if you want a subset, click Export, choose this message, the current view or the whole mailbox, then pick CSV (for Excel and Google Sheets), PDF or .eml. Open the CSV in Excel directly, or import it into Google Sheets with File → Import. Video: https://www.youtube.com/watch?v=kTDyo83cEf8 ### How do I download all Gmail attachments at once? Export your Gmail as an MBOX with Google Takeout (set the size to 50 GB to get one file), unzip it, open the .mbox at https://readmbox.com/ and use "Save attachments as ZIP" to get every attachment in one ZIP. You can limit it to images, PDFs, or documents and spreadsheets. Video: https://www.youtube.com/watch?v=NrCZk3-NfV4 ### How do I get a list of every email address in my Gmail? Back up Gmail to an MBOX with Google Takeout, open the file at https://readmbox.com/, click Export, choose CSV and tick "emails only". You get one row per address with counts of how many messages it sent you and how many you sent it. Open the CSV in Google Sheets or Excel and sort by count. Video: https://www.youtube.com/watch?v=gV_h79jOjhA ## Guides Step-by-step guides; each links back to the viewer on the homepage. Index: https://readmbox.com/guides/ - [I just downloaded Google Takeout. Now what?](https://readmbox.com/google-takeout-mbox/): Which file holds your mail, why it's one giant .mbox, and how to open and search it. - [Convert MBOX to Excel or CSV](https://readmbox.com/mbox-to-excel/): One row per email: date, from, to, subject, attachments and optionally the message text. - [Convert MBOX to PDF](https://readmbox.com/mbox-to-pdf/): A printable archive with a cover sheet, one message per page and page numbers. - [Open a large MBOX file (10 GB+)](https://readmbox.com/open-large-mbox-file/): Why big Takeout files crash other apps, and how to open one without importing anything. - [Extract every attachment at once](https://readmbox.com/extract-mbox-attachments/): Every attachment across thousands of emails in one ZIP, filtered by type if you like. - [MBOX file won't open](https://readmbox.com/mbox-file-wont-open/): The six usual reasons, from "still in the zip" to "too big for the app", and the fix for each. - [Thunderbird MBOX import not working](https://readmbox.com/thunderbird-import-mbox-not-working/): File not showing up, wrong folder, frozen on a big Takeout file: the fixes. - [Outlook can't open MBOX](https://readmbox.com/open-mbox-in-outlook/): Why Outlook can't do it, and the two ways around it: read it in a browser, or move it in as EML. - [MBOX Viewer vs Thunderbird](https://readmbox.com/mbox-viewer-vs-thunderbird/): An honest side-by-side, including when Thunderbird is the better pick. - [Open an MBOX file on Mac](https://readmbox.com/open-mbox-file-mac/): Apple Mail exports are folders, where Mac mail apps keep their mailboxes, and how to read them. - [Open an MBOX file on Windows](https://readmbox.com/open-mbox-file-windows/): Windows and Outlook can't, so here's what can, with no installer and no upload. - [Export email for a DSAR or lawyer](https://readmbox.com/export-email-for-dsar-ediscovery/): Find the relevant messages and hand them over as a CSV log, a PDF or original EML files. - [Leaving a job or closing Workspace](https://readmbox.com/keep-work-email-after-leaving/): Export the mailbox before the account goes, and read it any time later, privately. ## FAQ ### What is the best free MBOX viewer? For reading, searching and filtering without installing anything, MBOX Viewer at https://readmbox.com/ is free for files up to 50 GB and keeps the mail on your computer. Thunderbird (free, desktop) and Apple Mail (Mac only) can also open MBOX files but need to be installed and set up, and they import the mail into their own storage. ### Is my email uploaded anywhere? No. The browser reads the file from your disk using standard File APIs. There is no upload endpoint and no server-side mailbox storage. You can turn off Wi-Fi after the page loads and everything still works. ### How large a file can it open? Files of tens of gigabytes. The file is streamed in small chunks rather than loaded into memory. The free tier covers files up to 50 GB; above 50 GB the first 200 messages are free to browse, and the $29 unlock removes the limit. ### Do I need to install anything? No software, extension or account. Use desktop Chrome or Edge. ### Does it work on a phone? No. Mobile browsers cannot handle files of this size. Use a desktop or laptop. ### Can I open an MBOX file without Thunderbird or Outlook? Yes. Open it in the browser at https://readmbox.com/. Outlook cannot open MBOX files natively at all. ### Why won't my MBOX file open? Usually because the app you are using does not support MBOX (Outlook, Windows) or runs out of memory on a large Google Takeout file. On a Mac, an Apple Mail export is a folder ending in .mbox; the actual mail is the file named "mbox" inside it. Open that file. ### Are the original headers, dates and attachments kept? Yes. EML and MBOX exports are byte-exact copies of the original messages. CSV and PDF exports show the date, from, to and subject of each message. ### Can I export to .xlsx? Not directly. The export is CSV, which Excel and Google Sheets open as a spreadsheet; save as .xlsx from Excel if needed. ### Can it convert MBOX to PST? No. Export to EML and drag the files into Outlook instead. ### Can I use it for a DSAR or eDiscovery? Yes. Filter the mailbox to a date range, sender or subject, then export only the matching messages: a CSV list for your log, a paginated PDF for the record, or original .eml files or a smaller .mbox to hand over. Because nothing is uploaded, the personal data never reaches a third-party processor. ### Is it suitable for confidential or legal email? The mail never leaves your computer, so no third party ever has access to its contents. That makes it easy to use under confidentiality, privacy and data-protection requirements, but it is not a certified compliance product. ### What does it cost? Reading, searching and filtering are free for files up to 50 GB, as is exporting a single message. A one-time $29 unlock removes the size limit and enables bulk export in every format and bulk attachment extraction. No subscription. ## Limits - Desktop Chrome and Edge only; not mobile browsers. - No native .xlsx export (CSV opens in Excel) and no PST export (use EML). - PDF export is capped at 500 messages per file. - CSV body text is capped at 32,000 characters per message. ## Privacy - The .mbox file is read by the browser from local disk using standard File APIs. No message content, address, subject, filename or attachment is transmitted to any server, and none of it is stored anywhere. - There is no upload endpoint and no mailbox storage of any kind. - The website does use Google Analytics to count page visits, loads a web font from Google Fonts, and embeds a YouTube video via the no-cookie player. These relate to the page itself, not to mail data. Analytics never has access to mailbox contents. - Purchasing an unlock key involves Stripe checkout; the resulting key is validated against a licence endpoint. No mail data is involved in that exchange. ## Pricing - Free: read, search and filter any mailbox up to 50 GB, and export a single message. Above 50 GB the first 200 messages are free to browse. - One-time $29 unlock: no file size limit, bulk export in every format, and bulk attachment extraction. No subscription and no recurring charge. ## Videos - YouTube channel: https://www.youtube.com/@readmbox - What is an MBOX file?: https://www.youtube.com/watch?v=dvnQG92N51E - How to open and read MBOX files – 3 easy ways (ReadMbox, Thunderbird, Apple Mail): https://www.youtube.com/watch?v=ACbXU3-YlJY - Convert MBOX to Excel, Google Sheets (CSV), PDF and EML: https://www.youtube.com/watch?v=kTDyo83cEf8 - How to back up all your Gmail emails with Google Takeout: https://www.youtube.com/watch?v=9W7tzmwou7o - How to download all Gmail attachments at once: https://www.youtube.com/watch?v=NrCZk3-NfV4 - How to get a list of every email address in your Gmail: https://www.youtube.com/watch?v=gV_h79jOjhA ## Links - Homepage and app: https://readmbox.com/ - Features: https://readmbox.com/#what - Privacy explanation: https://readmbox.com/#privacy - FAQ: https://readmbox.com/#faq - Guides: https://readmbox.com/guides/ - Privacy policy: https://readmbox.com/privacy/ - YouTube channel: https://www.youtube.com/@readmbox - Support form: https://forms.gle/b8Rk2JJGoZmWjzUe9 ## Publisher One Scales Inc. — https://onescales.com/ Last updated: 2026-10