FlattenJson

Flatten nested JSON into the flat, delimited keys config systems expect — colon for .NET's secrets.json/IConfiguration, __ for Docker/Kubernetes/ASP.NET Core environment-variable overrides — instead of rewriting nested blocks by hand.

Example

Input — paste just the properties, no surrounding { } required:

// { surrounding braces are optional — making it easier to translate a subsection of your json
"ConnectionStrings": {
  "Default": "Server=.;Database=MyApp;"
},
"ApiKeys": {
  "Stripe": "sk_test_123",
  "SendGrid": "SG.abc123"
},
"AllowedHosts": ["localhost", [], "example.com"],  // empty containers (like this array) are skipped entirely
"Retries": 3,      // numbers, booleans, and null are preserved as-is, not stringified
"Debug": false,
"Timeout": null
// } Output is always a valid json with surrounding {} braces. 

Output — flattened with the default : separator (pick another via the separator picker):

{
  "ConnectionStrings:Default": "Server=.;Database=MyApp;",
  "ApiKeys:Stripe": "sk_test_123",
  "ApiKeys:SendGrid": "SG.abc123",
  "AllowedHosts:0": "localhost",
- "AllowedHosts:1"                  // never produced — the empty array contributes no key, so this index is skipped
  "AllowedHosts:2": "example.com",
  "Retries": 3,
  "Debug": false,
  "Timeout": null
}

Usage

1. Open the Command Palette (Cmd+Shift+P / Ctrl+Shift+P).
2. Run Flatten JSON.
3. Choose a source: Active Document, Active Selection, Clipboard, or Pick a File....
4. Choose a separator: :, ., __, /, _, or -. Your last pick is offered first.
5. The flattened result opens in a new unsaved JSON tab — copy it wherever you need it.

Requirements

None — works out of the box.

Extension Settings

This extension does not contribute any settings.

Release Notes

See CHANGELOG.md for release notes.

Development

• pnpm install — install dependencies
• pnpm run watch — build in watch mode
• pnpm test — run the test suite

See CLAUDE.md for architecture notes.