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A permissive row-level security (RLS) policy does not grant a PostgreSQL role permission to access a table. PostgreSQL checks ordinary SQL privileges and row policies as separate authorization layers, so either one can block a request. If a PostgREST-backed request returns HTTP 403, check the database error code, the role actually used for the request, and the grants and policies that apply to its operation—not just whether RLS is enabled.
Why a permissive RLS policy can still end in permission denied
PostgreSQL first requires the executing role to have the ordinary SQL privileges needed for the operation. RLS then controls which rows that role may see or modify. A policy that evaluates to true cannot compensate for a missing schema, table, or column privilege.
PostgreSQL’s documentation explains that, when row security is enabled, normal access to select or modify rows must be allowed by a row security policy. That policy is an additional authorization layer, not a substitute for SQL grants. PostgreSQL 18: Row Security Policies
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What a 403 tells you—and what it does not
HTTP 403 is an API response, not a PostgreSQL status code. In PostgREST, the database error code and message help identify the underlying failure. Its error reference maps PostgreSQL SQLSTATE 42501 to HTTP 403 for authenticated requests and HTTP 401 for unauthenticated requests. This mapping is specific to PostgREST; other gateways may handle database errors differently. PostgREST: Errors
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Capture the full response body, including the database code, message, and any details. Treat the HTTP status as a clue rather than proof that an RLS expression rejected a row.
Diagnose the failure in the order PostgreSQL evaluates access
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Identify the actual error
Record the full API error and determine whether the database code is
42501or a PostgREST-specific error code. Do not diagnose from the 403 alone. -
Find the request’s effective role
Check whether the request is authenticated and which database role it uses. A SQL editor, migration session, or administrator console may run as a different role than the application request. PostgREST authorization is role-based, and request claims can be exposed to policy expressions through transaction-scoped settings. PostgREST: Database Authorization
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Check ordinary grants independently
For that effective role, verify
USAGEon the schema, the needed table-level privilege, and any relevant column-level privileges. Account for inherited role memberships as well. A policy cannot make up for a missing grant. -
Inspect policies for the exact table, role, and command
Confirm RLS is enabled on the table involved and that an applicable policy targets the runtime role and operation. With RLS enabled, if no applicable policy allows access, PostgreSQL denies it by default. Also check policy type: applicable permissive policies combine with OR, while restrictive policies combine with AND. PostgreSQL 18: Row Security Policies
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Match the policy clause to the operation
USINGdetermines which existing rows are visible or may be targeted by operations such as update or delete.WITH CHECKdetermines whether proposed inserted rows, or the resulting rows of an update, are allowed. Policies can apply toSELECT,INSERT,UPDATE,DELETE, orALL. An expression that returns false or null does not authorize the row. -
Test as the application role, not only as an administrator
Reproduce the failing operation using the application role, or faithfully assume that role. Superusers and roles with
BYPASSRLSbypass row security. Table owners generally bypass it too, unless the table hasFORCE ROW LEVEL SECURITYenabled. An administrator’s successful query therefore does not establish that the application role is authorized.DriversOutdated Drivers Are Slowing You DownPerformancePC Slower Than It Used to Be?DriversCrashes, No Sound, or Screen Glitches?Special offer. See more information about Outbyte and uninstall instructions. Please review EULA and Privacy policy. -
Check objects referenced by policy expressions
If a policy calls a function or reads another table, verify the privileges required by those expressions as well. PostgreSQL evaluates policy expressions with the privileges of the user running the query. A
SECURITY DEFINERfunction can access data unavailable to its caller, so treat it as an intentional security boundary rather than a general-purpose workaround. PostgreSQL 18: Row Security Policies
Separate the likely causes before changing permissions
| Possible cause | What to verify | Evidence to compare |
|---|---|---|
| Missing SQL privilege | Schema USAGE, table privilege for the operation, relevant column privileges, and role memberships |
Effective role and complete database error |
| Policy does not allow the row | Applicable policy, role list, command, policy type, and USING or WITH CHECK expression |
Operation and whether the expression permits the existing or proposed row |
| Request uses a different role or authentication state | Role used by the request and whether it is authenticated | Compare the request context with the SQL editor or console role |
| API translates a database error | Gateway behavior and database SQLSTATE | HTTP status alongside the full error body; PostgREST documents its own 42501 mapping |
Changing a policy before confirming grants and the effective role can hide the symptom without fixing the authorization layer that failed. Use the database error and the operation’s exact role and policy context to choose the correction.
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