Clean CSV Online (Free, In-Browser)

CleanMySheet, a free in-browser tool, cleans CSV files without uploading them, applying deterministic rules for trimming, dates, duplicates, names, and phones, with strict mode ensuring column samples never leave the device. The tool, which supports up to 500 rows for free downloads, avoids AI-based rewriting to prevent data invention and offers a recipe and quality report for each cleaning.

CleanMySheet guide Clean a CSV online without uploading it CleanMySheet cleans CSV files entirely in your browser. Drop a file, review a scan of issues, apply presets trim, dates, duplicates, names, phones , then export. Strict mode is on by default so column samples never leave the device. Open the cleaner / Steps - Drop a .csv file or try the sample dataset - Read the scan: duplicates, dates, phones, empties - Apply recommended presets or search for a fix - Preview Original, Cleaned, and Diff - Download CSV free up to 500 rows plus a recipe and quality report What “clean CSV” actually means A messy CSV usually has extra spaces, mixed date formats 03/14/22 vs March 14 2022 , duplicate contacts, N/A placeholders, and names in Last, First order. Cleaning is applying reversible, named operations—not asking a chatbot to rewrite your rows. CleanMySheet records why each cell changed. Why not paste the file into ChatGPT? Large language models can invent values, drop rows, or reformat columns inconsistently. They also require you to send data to a server. CleanMySheet uses deterministic rules first dates, numbers, trim, dedup . Optional AI classification sends only column samples, and only if you turn Strict mode off. CSV vs Excel The same engine parses CSV PapaParse and Excel/XLSX SheetJS , including Excel serial dates and multiple sheets. If you have an .xlsx, use the clean Excel workflow; the recipe still exports as CSV for the MVP. Related searches this page answers - clean csv online - csv cleaner - fix messy csv - csv data cleaning tool