What does this tool do?
Deep merge two JSON objects into one, with control over how overlapping arrays are combined. Everything runs locally using JavaScript in your browser — nothing you paste or upload is ever sent to a server.
How to use this tool
- Paste your json a into the first box.
- Paste your json b into the second box.
- Fill in the when arrays overlap field above the input.
- Click Merge JSON.
- Copy the merged json from the output box.
Frequently asked questions
What happens when both objects have the same key?
If both values are objects, they are merged recursively. Otherwise, the value from JSON B wins and replaces the value from JSON A.
How are arrays merged?
Choose Concatenate to join both arrays end-to-end, or Overwrite to replace JSON A's array entirely with JSON B's array.
Can I merge more than two JSON objects?
Merge two at a time — run the tool again using the result as JSON A and your next document as JSON B.