Convert a JSON Dataset to Parquet for ML Work

JSON datasets are easy to share and slow to load. Parquet is smaller and keeps types. Here is how to convert.

Many public and scraped datasets come as JSON. Each record repeats every field name, so files are large, and reading them means parsing text. Parquet stores the data by column with a type for each, which loads faster and takes less space.

In the Format Converter choose JSON as the source and Parquet as the target, drop the file and convert. Nested objects become columns named by their path, numbers and dates are detected, and you can download the Parquet file and load it with pandas or DuckDB.

Check the result. Confirm the row count matches, check that numeric and date columns have the right types, and look at how lists were handled. Lists of simple values are kept as text in a single cell, so if a model needs them as separate features, do that step in your own code.

The conversion runs in your browser. Large files are limited by device memory, so use the large file mode for very big ones. Parquet is a storage choice, not a quality improvement: bad data stays bad.

Open the JSON to Parquet converter

Related tool pages

JSON, CSV, Parquet and Excel Converter: Convert between JSON, CSV, Parquet and Excel online for free, one file or a whole folder. It runs in your browser, so nothing is uploaded.
JSON to CSV Converter: Convert JSON to CSV in seconds. Drop a file or paste data and download the result. Private: it runs in your browser and nothing is uploaded. Large files too.
CSV to JSON Converter: Convert CSV to JSON in seconds. Drop a file or paste data and download the result. Private: it runs in your browser and nothing is uploaded. Large files too.
CSV to Parquet Converter: Convert CSV to Parquet in seconds. Drop a file or paste data and download the result. Private: it runs in your browser and nothing is uploaded. Large files too.
Parquet to CSV Converter: Convert Parquet to CSV in seconds. Drop a file or paste data and download the result. Private: it runs in your browser and nothing is uploaded. Large files too.
Parquet to JSON Converter: Convert Parquet to JSON in seconds. Drop a file and download the result. Private: it runs in your browser and nothing is uploaded. Large files too.

How to use the JSON to Parquet converter: step by step

Open the Format Converter and choose JSON to Parquet.
Drop in the dataset.
Convert and download the file.
Check the row count and column types after loading.

When to use the JSON to Parquet converter

Speed up loading of a JSON dataset
Store a dataset with real column types
Share a smaller file
Prepare data for DuckDB or pandas

Example

Input: [{"id":1,"name":"Ada","age":36},{"id":2,"name":"Alan","age":41}]

Output: A Parquet file with the same columns (id, name, age) and typed values.

Frequently asked questions

How do I convert JSON to Parquet?

Drop your JSON file (or paste the data), check the options, click Convert and download the Parquet result.

How big can a file be?

It depends on your device. A few hundred MB usually works.

Which conversions does the Format Converter support?

Any direction between JSON, CSV, Parquet and Excel (.xlsx), for one file or a whole folder. Nested JSON is flattened into columns such as address.city. For Excel, the first sheet is read; old .xls files are not supported.

Why did my number or date change after converting?

Types are detected from the values. Turn off "Detect types" to keep everything as text, which also keeps leading zeros in IDs and phone numbers.

Tip: Lists inside a record stay as text in one cell. Expand them in your own code if the model needs them.