# What is row-level security? Definition and Examples | Silicon

URL: https://meetsilicon.com/glossary/row-level-security/

> Row-level security restricts which rows of data a user can see, based on attributes such as their region, team or customer account.

In a well-governed setup the rule is defined once and applied to every query, including dashboards, exports, embedded views and AI answers.
## How it works
Each user carries attributes, such as region = EMEA or customer_id = 42. A rule on a table or model says which attribute filters which column, and the query engine adds that filter to every query the user runs. Column-level security works the same way for whole columns, such as hiding salary or personal data.
## Where it is enforced
Rules can live in the warehouse (Snowflake row access policies, BigQuery row-level security), in the semantic layer, or in the BI tool. Enforcing them in one place that every query passes through makes them easier to audit.
## How Silicon handles it
Silicon applies row- and column-level permissions to every query, including dashboards, exports, embedded views and AI analyst answers, because the AI runs each query as the person asking.
FAQ
## Row-level security questions
### Does row-level security slow queries down? +
Usually only slightly, since it adds a filter. Performance depends on whether the filtered columns are indexed or clustered.
### Does row-level security apply to AI assistants? +
Only if the assistant queries through the same layer that enforces the rules. An assistant with its own warehouse credentials can bypass them.
## Related
- Embedded analytics ->
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