How to allow download of .json file with ASP.NET

How can I enable the download of *.json files from an old ASP.NET site (IIS6 I am led to believe)?

I am getting a 404 page instead of the JSON file.

Do I need to create a web.config file? What goes in it?

If you want to manually add support to your site, you can just add the following to your web.config in the system.webServer section:

<staticContent>
    <mimeMap fileExtension=".json" mimeType="application/json" />
</staticContent>

This will add a "local" configuration under IIS. This does not work in IIS6, but does work in IIS7 and newer.

Add the JSON MIME type to IIS 6. Follow the directions at MSDN's Configure MIME Types (IIS 6.0).

• Extension: .json
• MIME type: application/json

Don't forget to restart IIS after the change.

UPDATE: There are easy ways to do this on IIS7 and newer. The op specifically asked for IIS6 help so I'm leaving this answer as-is. But this answer is still getting a lot of traffic even though IIS6 is very old now. Hopefully you're using something newer, so I wanted to mention that if you have a newer IIS7 or newer version see @ProVega's answer below for a simpler solution for those newer versions.

Solution is you need to add json file extension type in MIME Types

Method 1

Go to IIS, Select your application and Find MIME Types

Click on Add from Right panel

File Name Extension = .json

MIME Type = application/json

After adding .json file type in MIME Types, Restart IIS and try to access json file

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Method 2

Go to web.config of that application and add this lines in it

 <system.webServer>
   <staticContent>
     <mimeMap fileExtension=".json" mimeType="application/json" />
   </staticContent>
 </system.webServer>

When adding support for mimetype (as suggested by @ProVega) then it is also best practice to remove the type before adding it - this is to prevent unexpected errors when deploying to servers where support for the type already exists, for example:

<staticContent>
    <remove fileExtension=".json" />
    <mimeMap fileExtension=".json" mimeType="application/json" />
</staticContent>

Just had this issue but had to find the config for IIS Express so I could add the mime types. For me, it was located at C:\Users\<username>\Documents\IISExpress\config\applicationhost.config and I was able to add in the correct "mime map" there.

1. Navigate to C:\Users\username\Documents\IISExpress\config
2. Open applicationhost.config with Visual Studio or your favorite text-editor.
3. Search for the word mimeMap, you should find lots of 'em.
4. Add the following line to the top of the list: .