JSON Merge Tool

How to merge JSON files with the controls

1. Drop JSON files here or click browse files. Add two or more .json files, each containing one valid object or array.
2. Paste another document into the text area, optionally fill Document name (optional), and click Add document.
3. Select Object root (merge as key/value maps) or Array root (merge as top-level arrays). The documents must match the selected root type.
4. Choose Deep (recursive merge at every level) or Shallow (top-level keys only), then set Precedence for scalar & type conflicts and Null policy.
5. Set Global array handling. If you choose Merge by key, enter Global array merge key field. Add a path override when one array needs a different rule.
6. Review the Output tree and Every conflict & resolution. Then click Export merged JSON or Export merge report (JSON).

What deep merge JSON changes

Deep mode combines nested objects key by key. Shallow mode combines top-level keys, then treats a conflicting nested object as one value. With Last document wins, these inputs produce different results:

Document 1: {"profile":{"name":"Mina","role":"editor"}}
Document 2: {"profile":{"role":"admin","team":"data"}}

Deep:    {"profile":{"name":"Mina","role":"admin","team":"data"}}
Shallow: {"profile":{"role":"admin","team":"data"}}

How JSON array merge options work

Global array handling supplies the default for every array. A per-path override takes precedence at its exact dot-notation path, such as items or a.b.list. The tool does not validate that the path exists before merging.

• Replace keeps the array chosen by precedence.
• Concatenate appends arrays in source order.
• Union removes duplicates by deep value equality.
• Merge by key combines object items that contain the configured field. Items without that field stay in source order.

When Merge by key has no key field, the tool falls back to Replace and records an array-key-merge-missing-key conflict.

JSON merge errors and edge cases

Malformed JSON is rejected when it is added. The error can include a line and column. A top-level scalar is rejected because each source must be an object or array. A root-type mismatch blocks the merge, and the tool does not wrap the document. At least two valid documents are required.

Null is a value includes null in normal conflict resolution. Null means absent ignores null when another source has a real value, then keeps null when every source has null. Candidate values longer than 200 characters are shortened in the conflict display and report.

Examples of JSON Merge Tool use

• A developer combines base settings with an environment document. Deep mode keeps non-overlapping nested keys while precedence resolves repeated values.
• A data analyst combines record arrays with Merge by key, checks matched objects in the Output tree, and exports the merged JSON.
• A reviewer uses the conflict report to inspect candidate values before sharing the exported merge report.

Choose rules before exporting

Use JSON Merge Tool when object or array documents need named merge rules and conflict inspection. The parent JSON Merge Tools category lists other JSON merging workflows. Files are read in the browser, and the merged JSON and report are created as downloads.

Frequently asked questions