How to open a JSON file online
Three steps, a few seconds, no software.
Open your .MST file
Drop it on the box, choose it from your device, or paste the data straight in.
View the structure
Your .MST file opens as a tidy, foldable tree, with the exact line of any error pointed out.
Search, copy or download
Search keys and values, copy any path or value, switch to a table, or download a clean copy.
What is a .MST file?
The most common data format on the web.
An MST file is a Windows Installer Transform, a set of changes applied to an MSI installer to customize a software installation (features, settings, license keys, silent mode). You do not run it on its own; apply it with msiexec: msiexec /i app.msi TRANSFORMS=custom.mst /qn. To view or edit one, use Microsoft's free Orca tool from the Windows SDK.
Programs that open .MST files
| Full name | Windows Installer Transform |
|---|---|
| Developer | Microsoft |
| First released | Windows Installer (MSI) era, ~1999 (Office 2000 / Windows 2000) |
| Category | Text & Code |
| MIME type | application/octet-stream |
| Signature | D0 CF 11 E0 A1 B1 1A E1 OLE2 / Compound File Binary header (non-printable) |
Related viewers
Every viewer is free to use.
Frequently asked questions
Is my .MST file uploaded anywhere?
No. The file is opened directly from the copy you pick.
My .MST file is invalid. Can you fix it?
We show the exact line and column of the first error. For common problems like comments, trailing commas, single quotes or Python-style True/False/None, click Try to repair and download the fixed file.
How large can the file be?
Up to 50 MB. The tree only builds the branches you open, so even multi-megabyte files stay responsive.
What is JSONPath?
A path like $.orders[3].customer.email that points to one value inside the data. Click any node to see its path and copy it for code, jq or your API docs.
Can I see my data as a table?
Yes. Any array of objects can be shown in the Table view and downloaded as CSV.
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