Malloy
Malloy is a free, open-source language for describing data relationships and transformations.
What Malloy is
Malloy is a free, open-source language for describing data relationships and transformations. It lets users build semantic models with reusable calculations, table relationships, queries, and business logic, then compiles Malloy queries into SQL optimized for the connected database. Malloy supports nested data and automatically avoids common aggregate miscalculations involving sums, averages, and counts. Supported databases include DuckDB, MotherDuck, BigQuery, Databricks, Snowflake, PostgreSQL, MySQL, Trino, and Presto. DuckDB can read Parquet, CSV, and JSON files without additional setup. The Visual Studio Code extension supports model building, query execution, transformations, autocomplete, schema browsing, documentation, and visualizations. A browser notebook is available through github.dev and requires a GitHub sign-in. Malloy also has a Python package for DuckDB and BigQuery, plus a CLI for running files, building persistent tables, and automating pipelines. DuckDB connections can disable network access; sandboxed mode also restricts access to allowed directories. The downloadable CLI binary is not notarized on macOS and requires explicit permission in Privacy and Security settings.
Good
- Compiles queries into SQL optimized for the connected database.
- Supports nine listed databases.
- DuckDB reads Parquet, CSV, and JSON without extra setup.
- Avoids common aggregate miscalculations.
- Open source and free.
Watch out
- The github.dev notebook requires a GitHub sign-in.
- The macOS CLI binary is not notarized.
- Sandboxed DuckDB mode restricts file access to allowed directories.
Who it suits
Malloy suits SQL users who need reusable semantic models and work with its supported databases. It may also suit developers who want to build data workflows through VS Code, Python, or the CLI.
Verdict
Malloy brings semantic modeling, nested data, and query tools together in an open-source language. Consider the macOS CLI permission requirement and choose the editor or workflow that fits your setup.
The facts
Each one read from Malloy's own pages, with the date it was checked.
What it does
- Aggregations
- Malloy reuses aggregate computations across query granularities and says this helps improve accuracy.checked 7 Oct 2026
- Authoring
- The VS Code extension includes schema browsing, query execution, language autocomplete, documentation, and result visualizations.checked 7 Oct 2026
- CLI
- The Malloy CLI runs Malloy files, builds persistent tables, and can automate transformations and pipelines.checked 7 Oct 2026
- CLI limitation
- Malloy states that its downloadable CLI binary is currently not notarized on macOS and requires explicit permission in macOS Privacy and Security settings.checked 7 Oct 2026
- Credential security
- The VS Code connection editor stores sensitive values such as passwords and tokens in the system keychain.checked 7 Oct 2026
- Database integrations
- The documentation lists DuckDB, MotherDuck, BigQuery, Databricks, Snowflake, PostgreSQL, MySQL, Trino, and Presto as supported databases.checked 7 Oct 2026
- Editor support
- Malloy provides a Visual Studio Code extension for building models, querying and transforming data, and creating visualizations.checked 7 Oct 2026
- Intended users
- Malloy says it is immediately understandable to SQL users and easier to use and learn than SQL.checked 7 Oct 2026
- Local data files
- DuckDB support can read Parquet, CSV, and JSON files without additional setup.checked 7 Oct 2026
- Nested analysis
- Malloy supports nested query results, including fetching entire dashboards in a single query.checked 7 Oct 2026
- Nested data
- Malloy supports reading and writing nested datasets as a language feature.checked 7 Oct 2026
- Python package
- Malloy’s open source MIT-licensed Python package loads models, compiles queries, and runs statements, and currently works with DuckDB and BigQuery.checked 7 Oct 2026
- Query execution
- Malloy queries compile to SQL optimized for the connected database.checked 7 Oct 2026
- Safer aggregates
- Malloy automatically prevents miscalculating aggregates such as sums, averages, and counts.checked 7 Oct 2026
- Security controls
- DuckDB connections offer local and sandboxed security policies that disable network access; sandboxed mode also restricts file access to allowed directories.checked 7 Oct 2026
- Semantic modeling
- Malloy lets users define reusable calculations and business logic in a semantic data model.checked 7 Oct 2026
- Semantic models
- Malloy data models can encode reusable calculations, table relationships, and queries.checked 7 Oct 2026
- SQL output
- Malloy queries translate into SQL optimized for the connected database.checked 7 Oct 2026
- Support
- The project directs users to its Slack community to ask questions and share models, and to GitHub Issues for bug reports and feature requests.checked 7 Oct 2026
- Visualizations
- Malloy’s rendering library can use query metadata and results to render dashboards and visualizations and support drill through to detail.checked 7 Oct 2026
- What it is
- Malloy is an open source language for describing data relationships and transformations.checked 7 Oct 2026
Where it runs
- Browser use
- The Malloy extension works in VS Code Web, where it supports DuckDB with local CSV, JSON, and Parquet files; BigQuery, Snowflake, and PostgreSQL require VS Code Desktop.checked 7 Oct 2026
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