How to open a JSON file online
Three steps, a few seconds, no software.
Open your .FS file
Drop it on the box, choose it from your device, or paste the data straight in.
View the structure
Your .FS 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 .FS file?
The most common data format on the web.
An .fs file is an F# source code file, plain text that contains code for Microsoft's functional-first .NET language. Open it with Visual Studio 2022, VS Code with the Ionide extension, or any text editor. It is safe to view; risk arises only if you compile and run untrusted code.
Programs that open .FS files
| Full name | Visual F# Source File |
|---|---|
| Developer | Microsoft (F# language design by Don Syme, Microsoft Research) |
| First released | 2005 (F# 1.0, Microsoft Research); Visual Studio integration since 2010 (VS 2010) |
| Category | Text & Code |
| MIME type | text/plain |
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Every viewer is free to use.
Frequently asked questions
Is my .FS file uploaded anywhere?
No. The file is opened directly from the copy you pick.
My .FS 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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