JSON Merge Tool – Combine JSON Objects Online
Merge multiple JSON objects using configurable merge strategies. Our free JSON Merge Tool handles deep merges, overwrites, and conflict resolution for complex data structures.
About JSON Merge Tool
Merging two JSON objects sounds simple until you have nested structures. Should nested objects merge recursively or overwrite completely? This tool gives you control over the merge strategy, handling everything from shallow copies to deep recursive merges of complex nested data.
How the merge works
Paste your first JSON object and second JSON object in their respective panels. Choose a merge strategy from the dropdown: Deep Merge combines nested objects recursively, Shallow Merge overwrites nested objects entirely, and Overwrite replaces the first object with the second.
Click the Merge button and the result appears below. Properties from the second object take precedence when there are conflicts. Arrays are replaced, not concatenated. Use Copy or Download to export your merged JSON.
When you'd use this
You have a base configuration object and need to apply environment-specific overrides. Or you're combining API responses from multiple sources into a single object. This tool also helps when building up complex objects from partial data sources.
Note that this tool merges objects at the key level. Arrays get replaced entirely rather than merged element-by-element. For array merging you'd need custom logic based on your specific needs.
Questions
What's the difference between deep and shallow merge?
Deep merge recursively combines nested objects. Shallow merge only merges top-level keys, replacing any nested objects entirely with the second object's version.
How are array conflicts handled?
Arrays are always replaced, not merged. If both objects have a "tags" array, the second object's array wins completely.
Can I merge more than two objects?
Not directly. Merge two at a time, using the result as input for the next merge. Or use a programming language for batch merging.
What happens with null values?
Null is treated as a valid value. If the second object has null for a key, it overwrites whatever was in the first object.
Does this preserve the order of keys?
Modern JavaScript preserves insertion order for object keys. The merged result will have keys from the first object followed by new keys from the second.