Clean, merge and compare CSV in one place.
A fast, private CSV toolkit — auto-detect the delimiter, strip duplicates and empty rows, join two tables on a key, diff old against new, and convert between CSV and JSON. Everything runs in your browser; your files never leave the page.
Everything runs locally in your browser — no file is uploaded to a server.
Why DataForge
One-click cleaning
Trim stray whitespace, drop exact duplicate rows, and remove empty rows and columns. The delimiter is detected automatically, or pick it yourself.
Merge & join tables
Join two CSV files on a shared key column with inner, left or full-outer semantics — the same joins you would run in SQL, without a database.
Compare versions
Diff an old export against a new one, keyed on any column. See exactly which rows were added, removed or modified, with a colour-coded table.
Private & offline
Every file is parsed in your browser. Customer lists, exports and personal data never leave the page or touch a server.
CSV, cleaned up
DataForge is a free online CSV toolkit for the everyday chores of working with tabular data: cleaning a messy export, deduplicating rows after a merge, joining two spreadsheets on a shared ID, checking what changed between last week's file and today's, and converting a table to JSON for an API. Each job lives in its own focused tab, so you get a clear result — with a live table preview — instead of wrestling a dozen half-broken converters.
Everything runs client-side in your browser, which makes it fast, private and available offline once loaded. There is nothing to install and no account to create. Because the files you open never leave the page, it is safe to work with customer lists, financial exports and personal data. Robust parsing handles quoted fields, embedded commas and multi-line values correctly, and every feature is backed by a plain-language guide.
Guides & articles
Plain-language explainers on CSV files, data cleaning and the details behind tabular data.
What Is a CSV File? A Plain-Language Introduction
CSV is the lingua franca of tabular data — exported by every database, spreadsheet and analytics tool. Here is what it is, how it is structured, and the rules that keep it readable.
CSV Pitfalls: Delimiters, Quoting and Encoding
CSV looks trivial until a file opens as a single column or turns Cyrillic into garbage. Here are the three things that break CSV most often — and how to fix each.
CSV vs JSON vs Excel: Which Format When?
CSV, JSON and Excel all store data, but they are good at different jobs. A short, practical comparison to help you pick the right one — and convert between them cleanly.
Frequently asked questions
Are my files uploaded to a server?+
No. DataForge is a fully client-side application built on the 'privacy by design' principle. Every operation — parsing, cleaning, merging, comparing and converting — runs in your browser's JavaScript engine, and nothing is transmitted to a remote server. You can safely work with customer lists, financial exports and personal data (GDPR, 152-FZ); when you close the tab, nothing remains.
What is CSV and which delimiters are supported?+
CSV (Comma-Separated Values) is a plain-text format that stores a table as rows of values separated by a delimiter. Despite the name, the separator is not always a comma: DataForge supports comma (,), semicolon (;) — common in European locales where the comma is a decimal mark — tab (TSV) and pipe (|). Leave the delimiter on Auto and DataForge detects the most likely one; if detection is wrong, choose it manually.
How does the delimiter auto-detection work?+
DataForge inspects the content of the loaded file and picks the delimiter that produces the most consistent column count across the first rows, choosing among comma, semicolon, tab and pipe. This handles the vast majority of real-world files. If a file uses a rare separator, or contains many delimiter characters inside quoted values, pick the correct delimiter from the dropdown and reload the text.
How do I merge two CSV files?+
Open the Merge tab, load file A and file B, and pick the key column in each — the shared identifier such as an id or email. Then choose the join type: Inner keeps only rows whose key exists in both files, Left keeps every row from A and fills blanks where B has no match, and Full outer keeps everything from both sides. Run the merge to see a combined table and download the result as CSV.
Can DataForge convert between CSV and JSON?+
Yes. The CSV ↔ JSON tab converts in both directions. CSV → JSON turns the header row into object keys and each data row into an object, optionally inferring numbers and booleans so "42" becomes 42 and "true" becomes a real boolean. JSON → CSV accepts an array of objects (the most common shape) or an array of arrays, flattening nested values to compact JSON strings. Copy the output or download it.
Does DataForge support Unicode, Cyrillic and large files?+
Yes. DataForge reads files as UTF-8 and works correctly with any Unicode characters — Cyrillic, CJK ideographs and emoji. Files are processed entirely in your browser's memory, so the practical limit depends on your device's available RAM rather than a server quota; files up to a few tens of megabytes work smoothly. The on-screen preview shows the first rows for rendering speed, but every operation applies to the whole file, and the download contains all rows.