Guides
Practical, tool-agnostic guides on working with Parquet files. RSS
How to Check If a Parquet File Is Corrupted (No Install Needed)
Validate a Parquet file in your browser: check the footer and schema instantly, then scan every row group with one SQL query. No pyarrow, no Spark.
Combine Multiple CSV Files into One Parquet File
Turn a folder of CSV exports into a single compressed Parquet file with one DuckDB command, handling schema drift — or do it entirely in your browser.
How to Compare Two Parquet Files and See What Changed
Diff two Parquet files by key to find added, removed and changed rows — in your browser, with DuckDB SQL, or with a short pandas script.
Convert Parquet to CSV from the Command Line
Three ways to turn a Parquet file into CSV from a terminal — a DuckDB one-liner, Python with pandas or pyarrow — plus a no-install browser fallback.
DuckDB Parquet Viewer Options Compared: CLI, UI, and Browser
DuckDB can view Parquet files through its CLI, its local web UI, Python, or a browser-based tool. Here is how each works and when to pick one.
fastparquet vs pyarrow: Which Python Parquet Engine to Use
fastparquet and pyarrow both read and write Parquet from pandas, but they differ on speed, type support and maintenance. Here is how to choose.
How to Flatten Nested Parquet Columns to CSV or JSON
Parquet struct and list columns become unusable text in CSV. Flatten them properly with DuckDB SQL, or keep the nesting by exporting JSON instead.
How to Merge Multiple Parquet Files into One
Combine several Parquet files into a single dataset with DuckDB SQL in your browser — including files whose schemas don't quite match — or with pyarrow.
How to Open a Parquet File Without Spark or Python
Five ways to open and inspect a Parquet file — from zero-install browser tools to DuckDB one-liners — and when each one makes sense.
How to Open a Parquet File in Excel (Step by Step)
Excel cannot read Parquet natively. Convert the file to CSV in your browser — and trim oversized files with SQL first — to get it into a spreadsheet.
Fix pandas read_parquet: Unable to Find a Usable Engine
pandas raises ImportError: Unable to find a usable engine when no Parquet reader is installed. What actually causes it, and how to fix it for good.
PARQUET_COLUMN_DATA_TYPE_MISMATCH: Find Which File Drifted
Spark or Databricks fails reading a Parquet dataset when one file's column type changed. Here is how to find the drifted file and column, and fix it.
Parquet Compression: Snappy vs Gzip vs Zstd, Which to Pick
Snappy, Gzip, and Zstd trade file size for CPU time differently. Benchmarks, defaults by engine, and how to check or change the codec in an existing Parquet file.
Why Your Parquet Timestamps Are Wrong: The INT96 Problem
Timestamps shifted by hours, wrong by centuries, or rejected outright? Your Parquet file probably uses legacy INT96. What it is and how to deal with it.
Parquet "Magic Bytes Not Found" — What It Means and How to Fix It
The PAR1 magic bytes error means your Parquet file is truncated or not Parquet at all. Here is how to diagnose it in seconds and where the file broke.
Convert Parquet to JSONL for LLM Fine-Tuning
Fine-tuning APIs expect JSONL, but datasets ship as Parquet. Filter, reshape and export training data as JSONL — in the browser or with one DuckDB command.
Parquet vs CSV: Size, Speed and When to Use Each
A practical comparison of Parquet and CSV — file size, query speed, type safety and tool support — with concrete guidance on choosing.
Print a Parquet File's Schema Without Installing Anything
See a Parquet file's columns, types and row count in seconds — in your browser, with no pyarrow, Spark or parquet-tools. Works for multi-GB files.
Query Parquet Files with SQL — No Database Required
Run real SQL against local Parquet and CSV files using DuckDB in the browser: joins, aggregates and window functions with zero setup.
How to Read a Partitioned Parquet Dataset Without Spark
Query a directory of Hive-partitioned Parquet files with DuckDB SQL, filter by partition columns, and understand how partition pruning works.
How to Split a Large Parquet File into Smaller Files
Split an oversized Parquet file by target size, by row count, or by a column value — with DuckDB SQL, pyarrow, or in the browser with no install.