Unity Catalog versus Snowflake Polaris: which is more open?

Summary

• Both projects pass the basic open-source tests: each uses the Apache License 2.0, is developed in public on GitHub and sits in a vendor-neutral foundation.
• "Snowflake Polaris" now refers to two things: Apache Polaris, which Snowflake introduced in 2024 and which is now an Apache Software Foundation top-level project, and Snowflake Open Catalog, which Snowflake describes as "a managed service for Apache Polaris".
• The projects differ in scope. Apache Polaris is a catalog for Apache Iceberg, with generic tables (in beta) for other formats. Unity Catalog OSS governs Delta Lake and Iceberg tables plus volumes, functions and registered models.
• Both implement the Iceberg REST catalog API and vend short-lived storage credentials, so an engine with an Iceberg REST client can use either one for Iceberg tables.

Unity Catalog versus Snowflake Polaris: which is more open?

On license and governance they're level. Both are Apache 2.0 projects run inside open-source foundations, and both speak the open Iceberg REST catalog protocol. The real difference is how much of your estate each one opens. Apache Polaris is built for Apache Iceberg tables. Unity Catalog OSS is a multi-format catalog that also covers Delta Lake tables, unstructured files and AI assets. If every table you run is Iceberg, either project gives you an open catalog. If you also run Delta Lake, or want files, functions and models governed in the same namespace, Unity Catalog OSS handles those natively.

What each name refers to

Apache Polaris describes itself as "an open-source, fully-featured catalog for Apache Iceberg" that implements Iceberg's REST API. Snowflake introduced Polaris in 2024, and the project later moved to the Apache Software Foundation. The project announced its graduation from the Apache Incubator to a top-level project on February 19, 2026, and its latest release is 1.8.0. Snowflake Open Catalog is Snowflake's "managed service for Apache Polaris", hosted in Snowflake-managed infrastructure. Snowflake's documentation adds that new customers should use Snowflake Horizon Catalog, and that accounts that haven't previously created a Snowflake Open Catalog account can't sign up for a first one.
Unity Catalog comes in two forms too. Databricks open-sourced it in June 2024 as a Sandbox project of the LF AI & Data Foundation, and version 0.7.0 shipped on October 13, 2026. Unity Catalog in Databricks is the managed service built on the same open APIs.

Unity Catalog OSS vs Apache Polaris: how they compare on openness

Every cell comes from that project's own repository or documentation.

Openness criterion	Unity Catalog OSS	Apache Polaris
License	Apache License 2.0	Apache License 2.0
Foundation	LF AI & Data Foundation, Sandbox stage	Apache Software Foundation, top-level project
Published API specs	Unity Catalog REST API (OpenAPI), Iceberg REST catalog API, UC Delta API, Hive metastore API compatibility	Iceberg REST API, Polaris Management API, Polaris Catalog API
Table formats	Delta Lake and Apache Iceberg tables, plus formats such as Parquet, CSV and JSON	Apache Iceberg tables; generic tables (beta) for non-Iceberg formats such as Delta and CSV
Other governed objects	Views, metric views, volumes, functions, registered models	Iceberg views, generic tables, policies
Storage credentials	Short-lived credentials for tables, volumes, model versions and paths	Temporary storage credentials for engines; per its docs, the generic tables APIs don't support credential vending
Access control	Owners plus privileges granted to individual users; the OSS server has no groups or service principals	RBAC: privileges on catalog roles, granted through principal roles to principals
Managed service	Unity Catalog in Databricks	Snowflake Open Catalog

How to judge openness for your own stack

• Formats. A catalog is open only for the tables it can govern, so list the formats your engines write.
• Governance. Access rules should live in the catalog, not be rebuilt in each engine.

How Databricks approaches catalog openness

Databricks' published view is that an open catalog keeps your data in storage you own, gives those tables the full feature set, and lets them move to another catalog while the data stays in place. Managed Unity Catalog implements the same open APIs as the open-source project. External engines reach it through the Iceberg REST endpoint /api/2.1/unity-catalog/iceberg-rest, which serves managed Iceberg tables for reads and writes and Delta tables with Iceberg reads (UniForm) for reads. Delta clients such as Apache Spark and DuckDB use the Unity REST API to read and write Delta tables; creating and writing managed Delta tables this way needs catalog commits and is in Public Preview.
Access stays governed: a metastore admin turns on external data access (off by default) and grants EXTERNAL USE SCHEMA, and credential vending gives engines short-lived credentials that inherit the connecting principal's privileges. Unity Catalog can also read Snowflake managed Iceberg tables through catalog federation, and foreign Iceberg tables are read-only in Databricks. In the other direction, Snowflake can read Unity Catalog tables through a catalog integration that points at the same Iceberg REST endpoint. See Access Databricks tables from Apache Iceberg clients and What makes a catalog open?.

FAQs

Is Snowflake Polaris open source?

Apache Polaris is open source under the Apache License 2.0 and governed by the Apache Software Foundation. Snowflake Open Catalog is Snowflake's managed service for Polaris and runs on Snowflake-managed infrastructure.

Is Unity Catalog open source?

Yes. Unity Catalog OSS is Apache 2.0 code hosted by the LF AI & Data Foundation. Unity Catalog in Databricks is a managed service on the same open APIs that adds features such as automated lineage and audit logging.

Can one engine use both catalogs?

Yes, for Iceberg tables. Both implement the Iceberg REST catalog API, and Iceberg's Spark integration lets one session configure several named catalogs.

Does Apache Polaris support Delta Lake?

Polaris can register Delta tables as generic tables, which its docs mark as beta. The docs also state that Polaris provides no commit coordination for generic tables, so the engine handles commits. Unity Catalog OSS manages Delta tables directly, including catalog-managed commits through the UC Delta API.