Small, single-purpose tools that run entirely inside your browser. No account, no limit, no upload — so they stay usable for payroll, medical records, client lists and anything else covered by an NDA.
Drop a CSV, pick a category and a value column, get a bar or line chart. Groups case variants together and exports a vector SVG for slides.
Open the tool →Choose which columns make a row unique, see exactly which rows would go, keep the first or the last copy, and download the cleaned file.
Open the tool →Combine several exports into one file, matching columns by header name rather than by position, so a different column order still lines up.
Open the tool →Convert a CSV into JSON — objects, rows or NDJSON. Leading zeros, long identifiers and dates stay text instead of being mangled into numbers.
Open the tool →Open a CSV without Excel. Search across every column, sort by clicking a header, and see each value exactly as it is stored — no leading zeros eaten, no dates rewritten.
Open the tool →Break a large export into smaller files, every N rows or one file per column value. Every part keeps the header and they come back as a single zip.
Open the tool →How a page can read a file without uploading it. Browsers hand a page the contents of a file the user chose, through the File API — no network request is involved. Most online CSV tools upload anyway, because their processing happens on a server. These do not, and you can check: open your browser's network tab before dropping a file and watch the request list stay empty.
Each page does one thing and loads in well under a second, because it is one file with no frameworks, no external fonts and no trackers. That also means each one keeps working with the network off, and none of them can quietly change what they do with your data later.
Are these really free? Yes, with no account and no limit. They are single HTML pages with no server behind them, so there is nothing to meter.
How can a web page process a file without uploading it? Browsers hand a page the contents of a file the user chose, through the File API — no network request is involved. You can confirm it by opening the network tab before dropping a file: the request list stays empty.
Do they work offline? Yes. Once a page has loaded, you can disconnect and keep using it.
How large a file can they handle? Everything is held in memory, so they are comfortable up to a few tens of thousands of rows. Million-row files belong in a database or a desktop tool.
How to analyze a CSV without uploading it anywhere — why online tools ask for an upload, why it is almost never necessary, and the ten-second check that tells you whether a page is really processing your file locally.
Why Excel ruins CSV files — and how to stop it — leading zeros, scientific notation and dates, why Excel does it, and the settings that switch it off.
Sheet Insights reads an Excel or CSV file and builds the whole workspace — executive summary, trends with forecasting, a statistics centre, data quality checks and one-click cleaning. Same rule as these tools: everything runs in your browser, with no server behind it.
See what Sheet Insights does