Rowboat
rowboat.xyz/Welcome to Rowboat–a lightning fast tool for understanding large datasets. Sign in or create a free account to get started.
qsv.dathere.com - CSV data wrangling toolkit
qsv.dathere.com/qsv is a data-wrangling toolkit built with Rust to slice, dice, and analyze your data in seconds from the command line. Designed for very large data sets.
Jsonmatic
jsonmatic.com/Transform a CSV (spreadsheet) into a JSON.