JSON Merger: Combine JSON, CSV & Excel Files by a Shared Key | Tool by Ethan J. Hulbert

📦🤝 Ethan's JSON File Merger

If you have two JSON files that have the same values but different fields, you can combine them so the values have ALL of the fields, in one file. For instance, if your base file has ELEMENT1 with a:4 and b:7, and your new file has ELEMENT1 with c:9, this lets you combine them so your new file shows ELEMENT1 with a:4, b:7, and c:9. Matches any field shared between the two files. Also works well with CSV and Excel files, and between different formats!

Free Client-Side Only Updated 2026

Upload your two files

Pick a Base file, the one whose records and structure you want to keep, and a New file, the one whose extra properties get copied over. JSON, CSV, TSV, and Excel all work, and you can mix formats between the two sides.

Base data

The file whose records and overall structure get kept.

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New data

The file whose extra properties get copied onto matching base records.

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