Drag a CSV or TSV onto any Firefox tab and read it instantly as a sortable, filterable table — no link to open, no upload, no Excel. Fully local and open source.
Two ways to use it:
firefox-extension/— the Firefox / Zen extension: drag a.csv/.tsvonto any page and it opens as a table in a new tab. See firefox-extension/README.md for install & signing.viewer.html— a standalone single-file viewer. Open it in any browser and drop a CSV on it. Zero install, works offline, nothing leaves your machine.
The same code runs on Chrome via a one-line browser/chrome shim — only the MV3
manifest (chrome/manifest.json) and PNG icons differ. Build a loadable copy with:
bash build-chrome.sh # → dist/chrome/Then chrome://extensions → enable Developer mode → Load unpacked → pick dist/chrome/.
Note: for local file:// CSVs, turn on "Allow access to file URLs" on the
extension's details page (Chrome blocks file access by default). Dropping a CSV onto a
normal web page works without it.
- Type-to-filter across all columns (press
/to focus,Escto clear) - Click a header to sort (asc → desc → off); numeric columns detected and sorted as numbers
- Drag a header's right edge to resize columns; sticky header + first column
- Download the current view (filter + sort applied) back to CSV
- Light/dark via system theme
Everything runs locally in the browser. No network requests, no analytics — CSV data is read via the File API / in-memory messaging and never leaves your machine. Built for small files (≤ ~5k rows); every row is rendered, no virtualization.