About CSVUndo

CSVUndo was built by a developer who spent years watching the same small disaster repeat itself. An e-commerce coordinator opens a supplier feed to check one price, hits Save, and 40,000 UPC codes turn into 8.85E+11. An accounting clerk exports a customer list, and every New Jersey ZIP code drops its leading zero — 07030 becomes 7030 and the mail merge bounces. Nobody did anything wrong. Excel just “helped.” The manual fix was always the same twenty minutes — Data → From Text/CSV, setting each affected column to Text, re-exporting — twenty minutes nobody has when a marketplace upload closes in an hour.

The three core damage patterns

Nearly every mangled CSV we see falls into one of three buckets, so the site starts there:

• Scientific notation — long numbers such as EANs, tracking numbers, and account IDs collapsed into 1.23457E+12.
• Missing leading zeros — ZIP codes, SKUs, and employee IDs silently shortened.
• Broken characters — UTF-8 text garbled into José and “ by encoding mismatches.

From those three, the toolkit has grown to 10 free tools — adding a delimiter converter, cleaner, encoding checker, and merge/split/join tools, plus a one-click Shopify product CSV repair. See them all on the tools page.

Why everything runs in your browser

CSV exports often carry customer names, addresses, and order values — data you should never paste into a random website. So CSVUndo was designed client-side from day one. Your file is read with the browser’s own FileReader API, repaired in memory on your machine, and downloaded straight back to you. Nothing is transmitted anywhere, and there is no account to create. That is not a marketing promise; it is a technical claim you can verify yourself: load any tool page, switch off Wi-Fi, and run the repair. It works exactly the same offline.

Who writes these guides — and how we keep them honest

Every guide on CSVUndo is written and reviewed by the same people who build the tools — working developers who deal with real CSV exports, not filler spun up to rank. We fact-check each guide against primary sources: Microsoft’s own Office documentation, the CSV specification (RFC 4180), and the Unicode Standard, and we cite them inline so you can check anything yourself. Each guide carries a visible “last updated” date and is revised as Excel and the platforms change.

Our one firm rule: we would rather tell you a repair is impossible than pretend otherwise. Where Excel has permanently destroyed data — digits truncated past 15 significant figures, characters replaced with question marks on save — we say so plainly and point you to the only real fix, which is re-exporting from the source. A tool that over-promises wastes your afternoon; an honest one saves it.

What’s next

More repair modules are on the roadmap: date-format normalization (untangling 03/04/2025 ambiguity), delimiter detection for semicolon and tab files, and a batch mode for whole folders of exports. The guides section keeps growing alongside the tools, documenting prevention as well as repair.