Pad Column in CSV Files Online
Left-pad or right-pad a column in CSV files to a fixed width directly in your browser. Zero-pad numeric codes, pad product IDs to a fixed length, or right-pad text fields — no upload required.
How to pad Column in CSV files
- Drop your file onto the upload area. The first column is selected by default, and the first 200 rows are shown.
- Pick the column to pad and the pad side: Left pad (lpad, for 007) or Right pad (rpad, for 700).
- Set the total width in characters (1 to 200, default 10) and the pad character (one character, default 0). A live hint shows what "42" would become.
- Choose "Replace column in place", or "Append as new column" with a name (default: the column name plus _padded).
- Click Pad Column, check the preview, and download the file in the same format you uploaded.
Your file is processed locally in your browser and is never uploaded. The free limit is 50 MB per file; larger files work if your device has the memory for them.
Worked example
A retail store list was opened and saved in a spreadsheet, which turned US ZIP codes into numbers and dropped their leading zeros. The ZIPs must be five characters again before the file is matched against a postal database.
Input (CSV)
store_id,city,zip
S-014,Boston,2134
S-022,Jersey City,7302
S-031,San Francisco,94107
S-047,Holtsville,501Settings
- Column to pad: zip
- Pad side: Left pad
- Total width: 5
- Pad character: 0
- Output mode: Replace column in place
Result
| store_id | city | zip |
|---|---|---|
| S-014 | Boston | 02134 |
| S-022 | Jersey City | 07302 |
| S-031 | San Francisco | 94107 |
| S-047 | Holtsville | 00501 |
Each ZIP is converted to text and zeros are added on the left until it is five characters long. 94107 is already five characters and is unchanged. The zip column is now text, not a number, which is what keeps the zeros. A value longer than five characters, such as a ZIP+4 written as 021341234, would be cut to its first five characters.
Working with CSV files
The padded values are written to the CSV as plain text, such as 02134, without quotes. The file itself is correct. The risk is the next program that opens it: Excel and some CSV importers read 02134 as the number 2134 and drop the zeros again. Import the file with the column set to Text, or keep it in Parquet or JSON if it will be opened in a spreadsheet.
The loader often reads a column like zip as an integer, which is how the zeros went missing in the first place. Columns that already contain values with leading zeros, such as 007, usually load as text and keep them. Padding measures characters, so leading or trailing spaces in a CSV field count toward the width and can push a value over it. Run Trim Whitespace before padding if the source has stray spaces. Right-padding with spaces is the usual way to build fixed-width text fields, but most CSV readers keep trailing spaces, so the padded width survives a round trip.
Frequently Asked Questions
Why did my zero-padded CSV lose its zeros again?
The file is fine. The program that opened it converted the column back to numbers. Import the CSV with that column set to Text, or check the raw file in a text editor.
Do spaces in a CSV value count toward the pad width?
Yes. Width counts every character, including spaces. Trim the column first so padding is based on the real value.
What happens to values longer than the target width?
They are cut to the width. With a width of 5, "123456" becomes "12345" whether you pad left or right. Check the longest value in the column before choosing the width.
Can I pad with more than one character, such as "ab"?
No. The pad character box accepts a single character. An empty box falls back to 0.
Is the padded column still a number?
No. Padding converts the value to text first, so the result is always a text column. That is what lets it keep leading zeros.
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