Clean CSV data and Excel sheets
Clean CSV data in your browser, with no upload: trim spaces, drop blank rows, change letter case, fill or drop missing values and set column types, with a count of every change.
Process locally
Files stay in this browser session. Closing or clearing releases them.
Choose files
CSV, XLSX, JSON, one at a time
Drop files here, or
Adjust settings
Optional: Trim spaces, Columns to trim, Lowercase columns and more
Run
Processes in this browser; cancel at any time
About this tool
Clean CSV data before you import or analyse it: trim stray spaces, drop blank rows, make emails lowercase or codes uppercase, fill or drop missing values, and set column types such as numbers or dates. Excel and JSON files are cleaned the same way.
Everything runs in your browser and the file is never uploaded. The steps run in a fixed order, and a report counts every change, such as how many cells were trimmed or filled, so you can check what happened.
How to use it
- Choose or drop one CSV, Excel (XLSX) or JSON file and check its columns in the preview.
- Choose where to “Trim spaces”, leave “Drop blank rows” on, and tick any “Lowercase columns” or “Uppercase columns”.
- Decide how to handle “Missing values”: keep them, drop rows that have any, or fill text columns with the “Fill value”.
- Optionally set “Column types” for columns that should become numbers, dates or true / false values, and choose what to do with “Values that cannot convert”.
- Pick the “Output format”, then select Run and download the cleaned file and the report.
Formats and limits
- Input
- CSV, XLSX, JSON, one at a time
- Output
- CSV, XLSX, JSON
- Size limit
- 10 MB
- Settings
- Trim spaces (All text columns, Chosen columns, None); Columns to trim; Lowercase columns; Uppercase columns; Drop blank rows; Treat empty text as missing; Missing values (Keep as missing, Drop rows with missing values, Fill text columns); Fill value
- Privacy
- Files stay in the current browser session. No file bytes are uploaded.
- Price
- Free, no sign-up
Common questions
In what order are the steps applied?
Blank rows are dropped first. Then, cell by cell, spaces are trimmed, letter case changes, and empty text becomes missing if “Treat empty text as missing” is on. Column types are converted next, and finally rows with missing values are kept, dropped or filled.
What counts as a blank row?
A row whose cells are all empty or hold only spaces. Rows with at least one value are kept; use “Missing values” to drop rows that are only partly empty.
Why does a type conversion stop with an error?
When a value cannot become the chosen type, such as “n/a” in a number column, the run stops and names the row and column, so no value changes silently. Choose “Set missing and count” under “Values that cannot convert” to blank such values instead; the report counts them.
Which date format is accepted?
Dates convert from the ISO form 2026-03-15, optionally with a UTC time. Dates such as 15/03/2026 stay text, because the order of day and month cannot be told reliably. In Excel output, converted dates become date cells.
Does cleaning remove duplicate rows?
No. Run “Remove duplicates from CSV or Excel” on the cleaned file to drop repeated rows.
Is my file uploaded to a server?
No. Cleaning runs in your browser, so the data never leaves your device. Only the cleaned file and the report are created, for you to download.
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