The pgsessionjwt extension

Summary: The pg_session_jwt Postgres extension validates JWT tokens using a JWK and exposes auth.user_id(), auth.session(), and auth.uid() to extract the sub claim for use in Row-Level Security policies. It powers the Neon Data API, which installs and configures the extension automatically; without a JWK it falls back to PostgREST-compatible request.jwt.claims. Use this page when building custom auth setups outside the Data API or writing RLS policies that filter rows by authenticated user identity.

The pg_session_jwt extension

Handle authenticated sessions through JWTs in Postgres

Related resources

Source code

pg_session_jwt on GitHub

Important: The pg_session_jwt extension is automatically installed when you enable the Neon Data API for a branch. Do not install this extension manually.

The pg_session_jwt extension is a Postgres extension designed to handle authenticated sessions through JSON Web Tokens (JWTs). When configured with a JWK (JSON Web Key), it verifies JWT authenticity. When operating without a JWK, it falls back to using PostgREST-compatible JWT claims.

This extension powers the Neon Data API, enabling secure session management and Row-Level Security (RLS) based on user identity.

Features

JWT session initialization using a JWK (JSON Web Key) for secure JWT validation
Flexible authentication modes: use either JWK-validated JWTs or PostgREST-compatible JWT claims
User ID retrieval directly from the database for use in RLS policies
JSONB-based storage and retrieval of session information

How it works

The extension can operate in two modes:

With JWK validation

When a JWK is configured, the extension validates JWT signatures and extracts user information from verified tokens. This is the mode used by the Neon Data API.

With PostgREST-compatible JWT claims

When operating without a JWK, the extension works with PostgREST-compatible JWT claims via the request.jwt.claims parameter. This provides compatibility with PostgREST's JWT handling.

Functions

The pg_session_jwt extension provides functions in the auth schema:

auth.user_id()

Returns the user ID (sub claim) from the current session's JWT.

SQL

SELECT auth.user_id();

This function is commonly used in RLS policies to filter data by the authenticated user:

SQL

CREATE POLICY "Users can only see their own data"
  ON todos
  FOR SELECT
  USING (user_id = auth.user_id());

auth.session()

Returns the entire JWT payload as JSONB, giving you access to all claims in the token.

SQL

SELECT auth.session();

auth.jwt()

Alias for auth.session().

auth.uid()

Similar to auth.user_id() but returns UUID type. Expects the sub claim to be a valid UUID, otherwise returns NULL.

SQL

SELECT auth.uid();

Usage with Neon Data API

The pg_session_jwt extension is automatically configured when you enable the Neon Data API. The Data API handles JWT validation using your configured authentication provider's JWKS URL.

When making requests to the Data API, include your JWT in the Authorization header:

http

GET https://your-project.data.neon.tech/v1/todos
Authorization: Bearer <your-jwt-token>

The Data API validates the token and makes the user identity available via auth.user_id() for your RLS policies.

Usage with custom setups

For custom implementations outside of the Neon Data API, you can configure the extension manually:

Initialize with JWK

Set the JWK at connection time using libpq options:

Bash

export PGOPTIONS="-c pg_session_jwt.jwk=$MY_JWK"

Then in your session:

SQL

-- Initialize the session with the configured JWK
SELECT auth.init();

-- Set the JWT for the current session
SELECT auth.jwt_session_init('your.jwt.token');

-- Now you can use auth functions
SELECT auth.user_id();

Using PostgREST-compatible claims

When no JWK is configured, set claims via the request.jwt.claims parameter:

SQL

SET request.jwt.claims = '{"sub": "user-123", "role": "authenticated"}';
SELECT auth.user_id();  -- Returns 'user-123'

Warning: When using the fallback mode without JWK validation, request.jwt.claims is a regular Postgres parameter that can be modified by any database user. Ensure your application sets these claims securely before executing user queries.

References

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