Extract Head of Parquet Files Online
Extract the first N rows from Parquet files directly in your browser. Choose how many rows to keep and download the result — no upload required.
How to extract Head of Parquet files
- Drop your file onto the upload area. The whole file is loaded, the total row count is shown and the first 200 rows are previewed.
- Enter how many rows to keep in the Number of rows box. The default is 100.
- Click Extract First Rows. The preview switches to show only the rows you kept.
- Click Download to save them in the same format you uploaded, with _head added to the file name.
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 weather station logs a reading every ten minutes into one long file. An engineer wants a small slice to share in a bug report without sending the full year of data.
Input (Parquet)
Parquet file (binary, columnar) — shown as a table with its schema
| station | reading_time | temp_c | humidity_pct |
|---|---|---|---|
| WS-14 | 2026-07-01 00:00:00 | 11.4 | 82 |
| WS-14 | 2026-07-01 00:10:00 | 11.1 | 83 |
| WS-14 | 2026-07-01 00:20:00 | 10.9 | 85 |
| WS-14 | 2026-07-01 00:30:00 | 10.8 | NULL |
| WS-14 | 2026-07-01 00:40:00 | 10.6 | 86 |
Schema: station VARCHAR, reading_time TIMESTAMP, temp_c DOUBLE, humidity_pct BIGINT
Settings
- Number of rows: 3
Result
| station | reading_time | temp_c | humidity_pct |
|---|---|---|---|
| WS-14 | 2026-07-01 00:00:00 | 11.4 | 82 |
| WS-14 | 2026-07-01 00:10:00 | 11.1 | 83 |
| WS-14 | 2026-07-01 00:20:00 | 10.9 | 85 |
The first three data rows are kept in their original order and the header is carried over. Nothing is sorted, so "first" means first in the file, not earliest by timestamp. Here the file was already in time order, so the result is also the three earliest readings.
Working with Parquet files
Parquet has no header row, so N is simply the number of records. "First" follows the order the rows are stored in the file: the first row group, then the next. If the file was written by a job that ran in parallel, that order may not match any column, so check the preview before you rely on it being the oldest records.
The output is a new Parquet file with the same column names and types. Timestamps, decimals, lists and structs are carried over unchanged. Row groups and compression are rewritten for the smaller file, so it will not match the original byte for byte. A Parquet head file is a good way to share a schema sample with a colleague, since it opens in any Parquet reader with the real types intact. Head is also a cheap way to test a downstream loader. A 1,000-row Parquet file with the real schema will surface type mismatches in a warehouse load quickly, before you commit to the full file.
Frequently Asked Questions
Are the first rows of a Parquet file the oldest records?
Only if the file was written in that order. Parquet keeps rows in the order the writer produced them. Sort by your date column first if you need the earliest records.
Does the head of a Parquet file keep nested columns?
Yes. Struct, list and map columns are copied as they are, with the same schema as the source file.
Does it read only the first N rows?
No. The whole file is loaded into the in-browser engine and counted first, then the first N rows are kept. Very large files are limited by the memory your browser can use, not by N.
What is the difference between Head and Sample?
Head keeps the first N rows in file order and gives the same result every time. Sample picks rows at random, which is better when the start of the file is not typical of the rest.
What if I ask for more rows than the file has?
You get every row. If the box is empty or not a number, the default of 100 is used. 0 and negative numbers are treated as 1, so you always get at least one row.
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