About this CSV viewer
A tool for the ordinary moment when someone sends you a .csv and you just want to
see what is in it.
Why it exists
Opening a CSV should be boring, and it is not. Double-clicking one launches a spreadsheet that rewrites your data as it loads. The first search result for “online csv viewer” asks you to upload the file to a server. Anything over a few megabytes makes both of them crawl. None of this is necessary: browsers have been able to read local files since 2012.
How it works
When you pick a file, your browser reads it from disk, sniffs the character encoding from the bytes, decodes it, and parses the rows in memory. A table is then drawn — but only the rows in your viewport, recycled as you scroll, which is why a file with hundreds of thousands of rows still moves smoothly. Sorting, searching and editing all run over the parsed data in the tab. Exporting writes a fresh file from what is on screen.
There is no server component at all. The site is a set of static files; once the page has loaded, nothing else is fetched.
What it is built from
| Part | What |
|---|---|
| Site | Astro, built to static HTML |
| Parsing | Papa Parse — separator detection, quoted fields, line breaks inside values |
| Encoding | TextDecoder, with byte-level sniffing for UTF-8, UTF-16 and Windows-1252 |
| The grid | Written for this page — a few KB, virtualised, rather than a ~1.6 MB datagrid library |
| Offline | A service worker caching the shell, plus a web app manifest |
| Hosting | Static files on a CDN |
What it deliberately does not do
- No formulas, pivot tables or charts. It is a viewer. When you need to compute, export to TSV and paste into a spreadsheet.
- No accounts or saved files. There is nowhere to save to, which is the point. Close the tab and nothing remains.
- No analytics, cookies or trackers. The only thing stored on your device is whether you chose dark mode.
- No writing to your file. Your original is opened read-only and is never modified, even after you edit cells and export.
Verifying the privacy claim
Do not take it on trust — check it. Open your browser's developer tools, switch to the Network panel, clear it, and open a CSV. You will see no request. Or load the page, go offline entirely, and open a file: it still works, because there was never anything on the other end.
Read the privacy policy — it is short, because there is nothing to collect.