Open huge CSV files. Nothing uploads.
A fast viewer, cleaner and converter for CSV, TSV and Excel files that runs entirely in your browser. The 200 MB export your laptop chokes on opens here in seconds — with filters, dedupe, column stats and real exports.
- files up to 4 GB
- millions of rows
- xlsx & .csv.gz
- works offline
- free, no signup
Drop a CSV, TSV or Excel file here
.csv · .tsv · .txt · .csv.gz · .xlsx — files up to 4 GB open here, in your browser. Nothing is uploaded; the file is read in place on your device.
Filters combine with AND. Use the search box for a quick any-column match. Regex filters use JavaScript syntax.
Untick to hide a column (hidden columns are left out of exports). Type to rename — renames apply to exports too.
Exports include your filters, sort, edits and cleanups. Hidden columns are left out; renamed headers apply. The file is generated on your device — nothing is sent anywhere.
How it works
- Drop any CSV, TSV, .csv.gz or Excel file — up to 4 GB. It’s indexed in seconds and the row count appears immediately.
- Scroll millions of rows smoothly; search, filter, sort and profile columns — each operation streams through the whole file with a progress bar.
- Clean it: remove duplicates, trim whitespace, find & replace, edit cells, drop columns.
- Export as CSV, Excel, JSON, Markdown or SQL — or split into smaller files. All generated locally.
The engineering that makes 4 GB in a browser tab possible — byte-offset indexing, streaming passes, a virtualized grid — is documented on the how-it-works page. No black box, and no server: the same page explains how to verify the privacy claim yourself in 20 seconds.
Why a CSV tool should run locally
Think about what’s actually in the CSVs you handle: customer lists, payroll runs, patient schedules, transaction exports. The average “free online CSV viewer” asks you to upload exactly that to a server you know nothing about — a strange trade for a file format your own machine can parse in seconds. CSVLocal keeps the whole pipeline on your device: the file is read in place, processed in a local worker, and exports are assembled in your browser’s memory. Ads may eventually pay for the hosting — they will never see your data, because there is architecturally nothing to see.
Frequently asked questions
How is this different from opening the CSV in Excel?
Three ways. Scale: Excel’s grid ends at 1,048,576 rows and slows down long before that; this viewer streams and virtualizes, so multi-million-row files up to 4 GB stay smooth. Safety: Excel silently converts your data on open — leading zeros stripped, date-lookalikes rewritten — while this viewer shows bytes as they are. Privacy: nothing here is installed or uploaded; the file is read in place on your device.
Where does my file go when I drop it here?
Nowhere. The site is static — there is no server that could receive your file. Your browser reads the file from your own disk into a local web worker, and every operation (parsing, filtering, exporting) happens on your device. Verify it: open DevTools → Network while using the tool, or switch off Wi-Fi after the page loads — everything keeps working.
What file types can it open?
CSV, TSV and any delimited .txt (delimiter auto-detected among comma, semicolon, tab and pipe), gzip-compressed .csv.gz, and Excel .xlsx workbooks (pick a sheet; dates and leading zeros come out correctly). Files up to 4 GB; up to 256 MB is held in memory and larger files are streamed from disk.
What can I actually do with the data?
Search across all columns; add per-column filters (contains, equals, ranges, regex); sort; remove duplicate rows by any key columns; trim whitespace and fix casing; find & replace with regex and a preview count; edit individual cells; hide or rename columns; and profile every column (types, empties, distinct counts, min/max/mean, top values).
What export formats are there?
CSV with your choice of delimiter (comma, semicolon, tab, pipe, with an Excel-friendly UTF-8 BOM option), a real Excel .xlsx workbook, JSON or NDJSON with typed values, a Markdown table, SQL INSERT statements with optional CREATE TABLE, and a splitter that produces a ZIP of smaller CSVs. Every export reflects your current filters, edits and cleanups — and is generated on your device.
Is it really free? What’s the catch?
Free, no signup, no file-size teasing, no watermark. The plan is to eventually cover hosting with a few clearly-marked ads on the page — never inside your data, which stays on your device either way. There is no premium tier withholding features.
Does it work offline?
Yes — after the first visit the app caches locally, so it opens and processes files with no connection at all. Offline operation doubles as proof of the privacy claim: a tool with no network can’t be uploading anything.