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View a MSO file online, free

Open and read .MSO files online. View source, logs and text with syntax highlighting, search and line numbers, free.

Drop your .MSO file here

Opens your .MSO file right here.

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Up to 50 MB · 160+ text and code extensions
Instant. Opens in seconds
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100% free. No limits on use

What you get for a .MSO file

We don't have a dedicated viewer for this format, so we identify and inspect it instead — honestly, only what can be read from the file.

01

Drop your .MSO file

Choose it or drag it in. It's read right here in your browser.

02

We identify it

We read the magic bytes to tell what the file really is, its MIME type, and whether the name matches the contents.

03

See the details

Any metadata we can extract (dimensions, EXIF/GPS, document author and dates), a hex view, plus readable text and strings found inside.

What is a .MSO file?

Plain text that programs, servers and people write every day.

A .MSO file is a Microsoft Office Macro Reference File categorized as a data file. It contains information used by Microsoft Office applications and is not intended to be opened manually by a user.

Programs that open .MSO files

Windows
Microsoft Outlook, 7-Zip
macOS
Microsoft Outlook
.MSO format details
Full nameMicrosoft Office HTML/OLE Data Stream (oledata.mso)
DeveloperMicrosoft
First releasedcirca 1999–2000 (Office 2000 HTML mail/web-page export)
CategoryText & Code
MIME typeapplication/x-mso
Signature41 63 74 69 76 65 4D 69 6D 65 "ActiveMime"

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Frequently asked questions

Is my .MSO file uploaded anywhere?

No. The file is read and highlighted for you.

Why do some characters look wrong (é, ł)?

That usually means the file was saved in one encoding and opened in another. We detect UTF-8, UTF-16 and the Windows-1250/1252 code pages automatically and show which one was used.

Can it handle huge log files?

Yes, up to 50 MB. Only the lines on screen are drawn, so scrolling stays smooth. Syntax colours are switched off for files over 1.5 MB to keep things fast.

How do the log level filters work?

We find levels like ERROR, WARN, INFO and DEBUG on each line. Lines without a level, such as stack traces, stay with the entry above them, so filtering to errors keeps the full trace.

Can I edit the file?

This is a viewer. To change code, download it or copy it into your editor. Converting encodings and line endings is planned.

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