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Merge JSON Online — Free JSON Deep Merger

Deep merge two JSON objects — the second object overwrites and extends the first.

Step 1: Paste two JSON objects

Paste two JSON objects separated by a blank line. The second merges into the first.

+ How is deep merge different from spread?

Spread only does shallow merge. Deep merge recursively combines nested objects.

+ What happens to arrays?

Arrays from the second object replace arrays in the first.

+ Can I merge arrays?

Arrays at conflicting keys are replaced, not concatenated.

+ What are common use cases?

Config overrides, API composition, data patching, partial updates.