JSON Key Renamer

How to use this developer tool

1. Paste json and rename map or load a local file.
2. Review any available processing options.
3. Select Rename Keys or press Ctrl/Cmd + Enter.
4. Check the summary and diagnostics, then copy or download the result.

What this developer tool does

Rename JSON properties across an object tree with an explicit old-to-new mapping. Put the JSON first, add a blank line, then list one rule per line using old=new. Nested objects and objects inside arrays are covered. The tool stops on a target-key collision instead of silently overwriting data, which makes it safer for API payload migrations and fixture cleanup.

Nothing is uploaded by the core tool. Closing or refreshing the tab clears the current input.

Example

Input

{
  "first_name": "Ada",
  "profile": { "first_name": "Grace" }
}

first_name=firstName

Result

Run the sample to see the generated result and its statistics.

Use cases

• Review API payloads and fixtures before committing them.
• Diagnose generated JSON during development or testing.
• Prepare documentation, migrations, and typed interfaces.

Tips for reliable output

• Keep a copy of the original input before applying structural changes.
• Run invalid and edge-case samples as well as the happy path.
• Review warnings instead of treating generated output as a final contract.
• Use version control when replacing schemas or fixtures.
• Test downstream consumers after changing keys or required fields.

Processing details

JSON Key Renamer runs with standard browser JavaScript and uses JSON syntax as defined by JSON.parse except where raw-source inspection is required.

Application-specific validation rules and remote references are not inferred. Very large documents are limited by the memory available to the browser tab.