Direct comparison
Parquet vs CSV: File Format Comparison
Parquet vs CSV compared from the specs: RFC 4180 has no formal standard, Parquet has row groups, typed columns and nested data. See when to use each.
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How do CSV, Apache Parquet compare side by side?
The table below compares CSV, Apache Parquet across 11 procurement-relevant dimensions, from specification status through source.
Side-by-side comparison
| Dimension | CSV | Apache Parquet |
|---|---|---|
| Specification status | RFC 4180 is an informational memo that "does not specify an Internet standard of any kind" and states that "there is no formal specification in existence, which allows for a wide variety of interpretations of CSV files." | Apache Parquet is an open source file format; the parquet-format repository hosts "the official specification of the Parquet file format." |
| Orientation | Text records, one per line, with fields separated by commas. Records are separated by line breaks (CRLF in RFC 4180; some implementations use other line breaks). | Column-oriented: the Parquet overview describes it as a "column-oriented data file format designed for efficient data storage and retrieval." |
| Physical layout | A flat sequence of records. A header line is optional and, if present, is the first line. | Four-byte magic "PAR1", then data split into row groups, each holding one column chunk per column, then the file metadata, a four-byte metadata length and "PAR1" again. |
| Reading only some columns | Each record is a line of fields written one after another, so fields from different columns sit side by side in the file. | The file metadata is written after the data and contains the start location of every column chunk, so a reader reads the metadata first and then locates the column chunks it needs. |
| Data types | Everything is text. RFC 4180 registers the MIME type text/csv and defines no way to declare a type for a field; the reading tool decides how to interpret each value. | Declared physical types: BOOLEAN, INT32, INT64, INT96 (deprecated, used only by legacy implementations), FLOAT, DOUBLE, BYTE_ARRAY and FIXED_LEN_BYTE_ARRAY. The set is intended to be as minimal as possible. |
| Nested or complex data | RFC 4180 defines flat records of fields; it defines no nested structure. | Nested columns are encoded with the Dremel encoding, using definition and repetition levels. |
| Quoting and dialects | Fields may or may not be enclosed in double quotes, and an embedded double quote is escaped by doubling it. These are the points where files from different tools can differ. | Not applicable: values are stored under the typed physical types above, not as delimited text. |
| Writing the file | Records can be appended line by line. | File metadata is written after the data "to allow for single pass writing." |
| Tool support | The registered text/csv media type gives CSV a common label for exchange between programs. | Supported in many programming languages and analytics tools, according to the Apache Parquet overview. |
| When to pick each | Pick CSV when the file must be plain delimited text with the registered text/csv type and the data are flat records. | Pick Parquet when the data need declared types, nested columns, or reading selected columns without going through every record. |
| Source | IETF RFC 4180, "Common Format and MIME Type for Comma-Separated Values (CSV) Files" (rfc-editor.org/rfc/rfc4180), read 2026-10-29. | Apache Parquet documentation: Overview, File Format, Types and Nested Encoding pages (parquet.apache.org/docs), read 2026-10-29. |
Common questions
Common questions about CSV vs Apache Parquet
Is Parquet better than CSV?
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Neither is better in every case. Parquet is column-oriented, stores declared types and supports nested columns; CSV is flat delimited text with the registered text/csv media type. Choose by what the data and the next reader need: declared types, nested columns or column-selective reads point to Parquet; a plain flat text file points to CSV.
Is CSV a standard?
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Not formally. RFC 4180 is an informational memo that registers the text/csv MIME type and states that it does not specify an Internet standard of any kind; it also notes that no formal specification exists, which allows a wide variety of interpretations of CSV files.
Does Parquet have a formal specification?
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Yes. The Apache Parquet project documents the file format, and its parquet-format repository hosts the official specification.
How does Parquet store data on disk?
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A Parquet file starts and ends with the four-byte marker PAR1. Between them the data are split into row groups, each holding column chunks, followed by the file metadata and its length. Readers consult the metadata first to find the column chunks they need.
Does Parquet support nested data?
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Yes. Parquet encodes nested columns with the Dremel encoding, using definition and repetition levels. RFC 4180 describes CSV as flat records of fields.
Going deeper
