Read MBOX files on Mac & Windows.
Any size. Instantly.
Back up your Gmail with Google Takeout and read it offline. Open, search and export emails from MBOX and EML archives — from a few KB to 50+ GB — without your computer breaking a sweat.
macOS 14+ · Apple Silicon · Windows 10/11 and Windows Server
Built for one job, done right
Your Gmail, offline on your computer
Use Google Takeout to back up your entire Gmail account, then read, search and browse it offline — no internet required, no account login.
Other tools choke on large files
Most MBOX readers crash or freeze past a few hundred MB. Many ship a whole browser or JVM just to show a list of emails.
Native, streaming, instant
Mbox Viewer streams through files of any size without loading them into memory. Truly native on Mac and Windows. Indexes once, re-opens in under a second.
Features
Everything you need to live inside your email archive
A focused, native toolset — not a web app in a window.
Handles any size
Streaming parser with a 1 MB buffer opens files from a few KB to 50+ GB without loading them into RAM.
Instant re-opens
A binary index with SHA-256 validation makes every re-open take under a second, whatever the file size.
Powerful search
Full query syntax: from:, to:, subject:, body:, date:, has:attachment, size:>, OR, negation and exact phrases.
Gmail labels
Reads Gmail labels straight from Takeout. Browse by label in the sidebar with live message counts.
Full export
Export to EML, CSV, plain text or extract every attachment. Merge multiple MBOX files with dedup.
Conversation threads
The JWZ threading algorithm groups messages into conversations with reply chains up to four levels deep.
Privacy first
Everything runs locally. No cloud, no telemetry, no data ever leaves your computer. Strictly read-only.
Truly native
Native on Mac and Windows — dark mode, drag & drop, system share and print. No Electron, no Java.
Compatibility
Works with your email client
Mbox Viewer reads the standard mbox format — the same format virtually every email client and service uses for exports and backups. If your app can export mbox, Mbox Viewer can open it. No import, no conversion, no account: just open the file.
Apple Mail and Thunderbird now open directly, with no extra steps. Have Outlook (PST/OLM)? See how to convert it in our step-by-step guide.
Languages
Available in 18 languages
Mbox Viewer's interface and user guide are localized into 18 languages, so you can work through your email in the one you know best.
- English
- Español
- Deutsch
- Français
- Italiano
- 日本語
- 한국어
- Nederlands
- Polski
- Português (BR)
- Português (PT)
- Русский
- Svenska
- Dansk
- Norsk
- Türkçe
- 简体中文
- 繁體中文
Performance
Opens a 50 GB archive in under 5 minutes
And re-opens it in under a second — every time, thanks to the binary index.
| File size | Messages | First open | Re-open | RAM |
|---|---|---|---|---|
| 500 MB | ~5,000 | < 5 sec | < 1 sec | < 100 MB |
| 5 GB | ~50,000 | < 30 sec | < 1 sec | < 200 MB |
| 50 GB | ~500,000 | < 5 min | < 1 sec | < 600 MB |
Stop fighting your email backups
Free for files up to 500 MB. Unlock unlimited size with a one-time in-app purchase. No subscription, no account.