Pad Column in Parquet Files Online
Left-pad or right-pad a column in Parquet 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 Parquet 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 (Parquet)
Parquet file (binary, columnar) — shown as a table with its schema
| store_id | city | zip |
|---|---|---|
| S-014 | Boston | 2134 |
| S-022 | Jersey City | 7302 |
| S-031 | San Francisco | 94107 |
| S-047 | Holtsville | 501 |
Schema: store_id VARCHAR, city VARCHAR, zip BIGINT
Settings
- 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 Parquet files
Padding always produces a string column. If you pad an INT32 or INT64 column in replace mode, the Parquet output has a string column with the same name, so readers expecting an integer will need updating. Append mode keeps the numeric original and adds a padded text copy, which is safer for pipelines that already depend on the type. A minus sign is treated as an ordinary character, so -42 left-padded to 5 with zeros becomes "00-42", not "-0042".
Non-text types are converted to text using the engine's standard form before padding. A DECIMAL(10,2) of 12.50 becomes "12.50", a DOUBLE of 12.5 becomes "12.5", and a DATE becomes "2026-01-02". Large doubles can turn into scientific notation such as "1e+20", which is rarely what you want to pad. For fixed-width numeric codes, make sure the column is an integer or decimal type, not a float. Struct and list columns are rendered as text and padded as a whole, which is almost never useful.
Frequently Asked Questions
Does padding change the Parquet column type?
Yes. The padded column is always a string. Use Append mode to keep the original numeric column alongside the padded text.
How are decimal Parquet columns padded?
The value is converted to text with its full scale first, so 12.50 in a DECIMAL(10,2) column is padded as "12.50", including the decimal point.
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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