JSON Merger
Merge JSON files and objects online with deep merge, array concat/replace, and key conflict controls.
JSON Merger
Merge JSON files and objects online with deep merge, array concat/replace, and key conflict controls.
About JSON Merger
Merge JSON files and objects online
Paste JSON files, API responses, config snippets, or object payloads into separate inputs and merge them into one JSON document. Nested objects are combined recursively, so environment overrides, fixtures, and datasets can be layered without manually copying fields.
Control duplicate keys and arrays
When the same key exists in multiple JSON inputs, choose whether later values override earlier ones or the first value wins. Arrays can be concatenated or replaced, matching either additive data consolidation or strict config override behavior.
Formatted output for review
The merged JSON output is stringified with the selected indentation, making it easier to inspect before copying or downloading as a file. All parsing and merging happen locally in the browser, so draft payloads do not need to leave your machine.
FAQ
Common questions and answers about this topic.
What does this tool do?
It combines two to five JSON files, documents, or object snippets into one merged JSON output. Use it for API payloads, configuration files, fixtures, and datasets when you need an online JSON merger or combiner.
How are conflicts handled?
Use the key conflict option to decide which value wins when multiple JSON inputs contain the same key. By default, later inputs override earlier ones, but you can switch the direction without reordering the inputs.
Does it merge nested objects?
Yes, nested objects are deep-merged recursively instead of being replaced as a whole. This is useful when combining config layers, API response fragments, or JSON fixtures that share the same object structure.
Is my data sent to any server?
No, JSON merging is handled entirely in your browser. Both documents are merged locally with JavaScript — no data is sent to any server.
How are arrays handled during merge?
You can choose between two array strategies — concat, which appends later arrays to earlier arrays, or replace, which uses the later array entirely. Concat is the default for additive JSON merging.
How many JSON inputs can I merge at once?
Up to five JSON files, documents, or object snippets can be merged in a single run. Use the "Add input" button below the second input to add more inputs; they are merged left-to-right.
Can I change which input takes precedence?
Yes. The "Key conflict" dropdown lets you switch between "B overrides A" (default) and "A overrides B" on key conflicts, without re-ordering your inputs.
Can I download or copy the merged result?
Yes. Use the download icon on the output panel to save the merged JSON as a file, or the copy button to put it on your clipboard for pasting into code, tests, or documentation.