Merge Parquet Files Online
Merge and concatenate multiple Parquet files into one, directly in your browser.
How to merge Parquet files
- Click the upload area to add your first file. It is loaded in the browser and listed with its row and column count.
- Click + Add File to add the next file, one at a time. Use Remove next to any file you added by mistake. If the files do not all have the same columns, a note says so. They still merge, matched by column name.
- Once two or more files are listed, click Merge Files. Rows are stacked in the order the files were added, and the total row count is shown.
- Check the preview of the first 200 rows, then click Download merged to save merged_result in the same format.
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
Two regional teams send in their July expense sheets. The south team lists the columns in a different order and adds a category column the north team does not use. The north file is shown below.
Input (Parquet)
Parquet file (binary, columnar) — shown as a table with its schema
| rep | expense_date | amount |
|---|---|---|
| Ines | 2026-07-01 | 120.5 |
| Ines | 2026-07-08 | 33 |
| Marek | 2026-07-02 | 210 |
Schema: rep VARCHAR, expense_date DATE, amount DOUBLE
Settings
- File 1: north expenses (shown above)
- File 2: south expenses, columns amount, rep, expense_date, category, with rows (54.2, Kofi, 2026-07-03, meals) and (18, Kofi, 2026-07-09, parking)
Result
| rep | expense_date | amount | category |
|---|---|---|---|
| Ines | 2026-07-01 | 120.5 | NULL |
| Ines | 2026-07-08 | 33 | NULL |
| Marek | 2026-07-02 | 210 | NULL |
| Kofi | 2026-07-03 | 54.2 | meals |
| Kofi | 2026-07-09 | 18 | parking |
Columns are matched by name, not position, so the south file's amount values land under amount even though that column comes first in its file. Column order follows the first file, and category is added at the end because only the second file has it. North rows get NULL for category. Rows keep file order: first file, then second.
Working with Parquet files
Merging Parquet files is a quick way to compact many small part files, such as the output of a streaming job or a partitioned export, into one file that is easier to share or load. Columns are matched by name, so files written by different versions of a pipeline still merge when a newer version added a column. Older files get NULL in the new column.
When the same column has different types in different files, the engine picks a type that can hold both. INTEGER and BIGINT become BIGINT, and a number merged with a string becomes a string. Check the column types in the preview after merging. Struct columns with different fields are combined into one struct with all the fields. A struct in one file and a plain value in another cannot be combined, and the merge stops with an error. The output is a single Parquet file with the combined schema.
Frequently Asked Questions
Can I merge Parquet files whose schemas changed over time?
Yes, as long as the differences are added or missing columns or compatible types. Missing columns are filled with NULL. A column that is a struct or list in one file and a plain value in another will stop the merge with an error.
Is this a good way to compact small Parquet files?
Yes, for files that fit in browser memory. Add the part files, merge them, and download one Parquet file with the combined rows.
Do all files need exactly the same columns?
No. Columns are matched by name, ignoring case. A column missing from one file is filled with NULL for that file's rows, and columns can appear in any order.
Is this a join on a key column?
No. Merge stacks rows from one file under another, which SQL calls UNION ALL. To match rows from two files on a shared ID, use the SQL Query tool with a JOIN.
Are duplicate rows removed when merging?
No. Every row from every file is kept. Run Remove Duplicates on the merged file if the inputs overlap.
Related Tools
Deduplicate Parquet Files Online
Remove duplicate rows from Parquet files instantly in your browser. No upload, no server — 100% private.
Sort Parquet Files Online
Sort Parquet files by any column, ascending or descending, directly in your browser.
Aggregate Parquet Files Online
Group and aggregate Parquet files by any column directly in your browser. Calculate sum, average, min, max, and count for any numeric column — no upload required.
Merge CSV Files Online
Merge and concatenate multiple CSV files into one, directly in your browser.
Merge Excel Files Online
Merge and concatenate multiple Excel files into one, directly in your browser.
Merge JSON Files Online
Merge and concatenate multiple JSON files into one, directly in your browser.
Parquet Viewer Online
View and inspect Parquet files directly in your browser. Browse rows, check column names and data types — no upload required, your data stays on your device.
Convert Parquet to CSV Online
Convert Parquet files to CSV format directly in your browser. No upload required — your data never leaves your device.