twineconvert

free · in-browser · no upload

CSV to DAT
Converter

Drop your CSV file. We'll convert it to DAT right here in your browser, your file never leaves your device.

or drop your file

Select your file here to get started

or drop your file here.

Accepts .csv

nothing uploaded no file size cap no signup

How it works

Three steps. No upload, no signup.

  1. 1

    Drop your file

    Click the dropzone above or drag a CSV from your desktop. Files of any size, there's no upload, so there's no upload limit.

  2. 2

    Convert in your browser

    The conversion runs entirely in this tab using JavaScript and WebAssembly. Your file never touches our servers, we don't have any.

  3. 3

    Download

    Get your DAT the moment the conversion finishes. Convert another, or close the tab.

Files stay on your device

Your file is never uploaded. The entire conversion runs in your browser using WebAssembly. We can't see what you convert because we have no server to see it.

No file size limit

Server converters cap free users at 1-2 GB and gate larger files behind a paid plan. Since nothing uploads, our limit is whatever your browser can handle.

Free, no signup, no ads on conversions

No account required. No watermark on the output. No queue. Drop a file, get a converted file.

Why convert CSV → DAT

What this conversion is actually for

If you've built up a custom document set in a spreadsheet (from a database export, an ad-hoc collection, or a third-party platform that doesn't speak DAT), getting it into Relativity or Concordance for review requires a proper DAT file with the Unicode delimiters and text qualifiers their importers expect. Producing one by hand is error-prone — wrong delimiter, wrong line terminator, missing header line, and Relativity rejects the entire load.

A real example

Your client's IT team exported a custom email database as CSV with columns `BegBates, EndBates, From, To, Subject, BodyText`. You need it in Relativity for review. Convert to DAT, hand to the litigation support team, they load it without further reformatting.

Troubleshooting

Relativity's import wizard rejects my DAT with 'invalid delimiter' errors.

Some Relativity instances are configured to expect the visible-character delimiter pair (`|`/`"`) instead of the Unicode pair we emit by default (which is the Concordance standard). Confirm with your litigation support contact which delimiters their workspace expects. If Unicode, our output works as-is.

Bates ranges look wrong after import.

Make sure your CSV has explicit `BegBates` and `EndBates` columns (not just a single `BatesNumber`). For one-page documents, BegBates = EndBates. Most review platforms require the range explicitly.

Formats involved

About CSV and DAT

CSV, Comma-Separated Values

CSV is plain text, one row per line, fields separated by commas. The simplest possible tabular data format, which is exactly why it remains the most portable: every spreadsheet, database, programming language, and analytics tool reads CSV. Tradeoffs: no formulas, no formatting, no multiple sheets, and various edge cases around quoting fields that contain commas or newlines.

How to open

Excel, Google Sheets, Apple Numbers, LibreOffice Calc, any text editor, every database import wizard, every programming language with one line of code.

Full CSV format guide →
DAT, Concordance/Relativity load file

DAT is the metadata + extracted-text load file format every U.S. eDiscovery production uses. Produced by Concordance, Relativity, Reveal, Logikcull, Everlaw, and every law firm review platform. Uses non-printable Unicode characters (U+0014 field delimiter, U+00FE text qualifier) instead of CSV's commas + quotes — the unusual delimiters avoid collisions with quoted text inside fields like email body content. CRLF line terminators (Concordance is Windows-native).

How to open

Concordance, Relativity, Reveal, Everlaw, Logikcull, and every other eDiscovery review platform load DAT files natively. Excel opens them but shows garbled þ characters. Convert to CSV for spreadsheet workflows; the original DAT remains the production-of-record format.

Full DAT format guide →

Convert your CSV to other formats

FAQ

Common questions

Is this CSV → DAT converter really free?

Yes. No signup, no watermark, no daily file count limit. Every conversion runs in your browser, your file never touches our servers because there are no servers.

Where does my file go when I convert it?

Nowhere. The conversion runs entirely in your browser using JavaScript and WebAssembly. Your file is never uploaded to our servers. We don't have any servers handling files, there's nothing for us to log, store, or accidentally leak.

What's the maximum file size?

Whatever your browser can hold in memory. Practically, this means a few hundred MB on most computers, significantly larger than the 1-2 GB caps that server-upload converters charge for. Very large files (multi-GB) may require closing other browser tabs first.

Why convert CSV to DAT?

Universal tabular data interchange. eDiscovery document production metadata exchange between law firms. The most common reason to convert is compatibility, DAT works in places where CSV doesn't, or vice versa.

How do I open a CSV file in the first place?

Excel, Google Sheets, Apple Numbers, LibreOffice Calc, any text editor, every database import wizard, every programming language with one line of code.

Does this work offline?

Once the page is loaded, the conversion itself runs entirely offline. The first time you use a tool, your browser downloads the conversion library (a one-time cache). If you reload while offline, the page won't load, but you can install the site as a Progressive Web App for full offline use.

Can I convert multiple files at once?

Single file at a time for now. Batch conversion is on the roadmap, for now, drop one file, download the result, then convert the next.