About CSVLocal

CSVLocal exists because of a specific, recurring absurdity: you have a CSV on your own computer, and the standard advice for opening it is to either fight Excel (which truncates it at a million rows and quietly rewrites your data on the way in) or upload it — your customer list, your payroll export — to a stranger’s server that happens to run a parser you could be running yourself.

So this site runs the parser on your machine instead. Modern browsers are genuinely fast: with a streaming index and a virtualized grid, a multi-gigabyte file opens in seconds on a normal laptop, and filtering, deduplicating, profiling and converting are one-pass operations — no install, no account, no upload. The how-it-works page explains the engineering; the short version is that “too big for Excel” was never actually big.

The honest business model

The site is free and there’s no premium tier. If it earns enough traffic, clearly-marked ads on the page will cover hosting — with the structural guarantee that ads can never see your data, because your data never leaves your device. Until then it costs almost nothing to run, which is the advantage of having no servers doing file processing.

Who makes this

An independent developer who has spent years moving large datasets through pipelines and wanted the ten-second version of those tools to exist in a browser tab. This site is one of a small family of single-purpose, local-only utilities built on the same principle; each stands on its own, and none of them upload anything.

Found a file it mishandles, or a feature it’s missing? Tell us — files that break parsers make the tool better for everyone.