Add Cumulative Sum to JSON Files Online
Add a running total column to JSON files for any numeric column. Optionally order by a date or sequence column and restart totals per group — no upload required.
Drop your .json file here
or click to browse — max 50 MB
Frequently Asked Questions
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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