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Local-only

XLSX, CSV or JSON

Spreadsheet converter

SheetJS processes the first worksheet locally for CSV and JSON output.

Private local processingEngine v1 · free local pack

Output format

Local-processing contract

Input is read with browser File APIs.
Heavy work runs in a disposable worker or FFmpeg’s local worker.
Output is retained in OPFS or IndexedDB when available.
No upload endpoint exists in this static project.

Engine

Browser APIs + JavaScript libraries

filesweb-workeropfsindexeddb

Important limits

• CSV and JSON output use the first worksheet only.
• Advanced charts, macros and Office layout are outside this deterministic converter.

Need detailed editing?

UsefulUtility performs exact transformations. Open the result in the appropriate ZenBinary specialist app for layers, timelines, layouts or semantic editing.

UUsefulUtility

Exact input + exact operation + reproducible output. Supported processing runs on this device unless you explicitly choose an online export action.

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