Merge JSON Files Online

How to Merge JSON Files Online

Working with multiple JSON files is a common task for developers, data analysts, and anyone dealing with configuration files or API responses. Our JSON merger tool lets you combine two or more JSON structures directly in your browser without uploading anything to a server — ensuring complete privacy and instant results.

Three Merge Modes Explained

Object Merge: Combines JSON objects using the spread operator principle. Later values overwrite earlier ones for duplicate keys. This is the fastest way to merge two config files or combine objects with non-overlapping keys.

• Input 1: {"name": "Alice", "age": 30}
• Input 2: {"city": "NYC", "age": 31}
• Result: {"name": "Alice", "age": 31, "city": "NYC"}

Array Concat: Concatenates JSON arrays into a single array. Perfect for combining lists of items, database records, or API paginated results.

• Input 1: [1, 2, 3]
• Input 2: [4, 5, 6]
• Result: [1, 2, 3, 4, 5, 6]

Deep Merge: Recursively merges nested objects. Instead of overwriting entire nested objects, it merges their properties level by level. Arrays within objects are concatenated. This is ideal for merging complex nested configurations.

• Input 1: {"db": {"host": "localhost", "port": 5432}}
• Input 2: {"db": {"port": 3306, "user": "admin"}}
• Result: {"db": {"host": "localhost", "port": 3306, "user": "admin"}}

Why Use This JSON Merger?

Unlike server-based tools, our merger runs entirely in your browser using JavaScript. Your data never leaves your device, making it safe for sensitive configuration files, API keys, or personal data. There is no file size limit beyond your browser's memory capacity, and results are generated instantly with no network round-trips.

You can merge JSON by pasting text directly or by dragging and dropping .json files from your computer. Add as many JSON inputs as you need — the tool handles them all in the order they appear, applying the selected merge strategy sequentially.