Add Conditional Column to JSON Files Online
Add a new column to JSON files based on an if/else condition directly in your browser. Set a value for rows that match and a different value for rows that don't — no upload required.
About this tool
Add a new column to a JSON file whose value is determined by conditions you define — like an Excel IF statement or SQL CASE WHEN. Set as many rules as you need, choose a value for each matching condition and a fallback for everything else, then download the updated file. All processing runs locally in your browser.
Frequently Asked Questions
What is a conditional column in a JSON file?
A conditional column adds a new column whose value is determined by rules you define — equivalent to SQL CASE WHEN. For example: if score > 90 then "A", if score > 80 then "B", else "C". Each row gets the label from the first condition it satisfies.
Can I add multiple conditions when creating a conditional column in a JSON file?
Yes. Add as many WHEN conditions as you need. Conditions are evaluated top to bottom and the first match wins. The final ELSE clause sets the value for any row that matches none of the conditions.
What data types can I use in conditional column expressions for JSON files?
Text, numeric, and date comparisons are all supported. Operators include equals, not equals, greater than, less than, contains, starts with, ends with, is null, and is not null.
Is my data private?
Yes — completely. Your file is never uploaded to any server. Everything runs locally in your browser using WebAssembly — processing happens entirely inside your tab. Once you close the tab, nothing is retained.
What is the maximum file size?
The free limit is 50 MB. For larger files, performance depends on your device's available memory — most modern machines handle 500 MB to 1 GB comfortably.
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