Keycloak UI Error: unknown_error / Cannot parse the JSON when Adding Audience Mapper #42784

Ritikkumar352 · 2025-09-20T11:03:34Z

Ritikkumar352
Sep 20, 2025

Keycloak UI Error: `unknown_error` / Cannot parse the JSON when Adding Audience Mapper

Environment

Keycloak Version: 26.3.4 (from Docker image quay.io/keycloak/keycloak:latest)
Database: PostgreSQL 15
Environment: Running in Docker
Browser: FireFox

Goal

I am setting up a confidential client for a Spring Boot backend.
My goal is to add the client's own clientId to the aud (audience) claim in the access token so my backend can validate it.

Expected Behavior

When I navigate to:
Client -> Client scopes -> [client-id]-dedicated -> Mappers -> Add "Audience" mapper

I expect the mapper to be created successfully after clicking Save.

Actual Behavior

The UI displays a generic error popup:
Could not create mapping: 'unknown_error'
The browser's developer console may show a Cannot parse the JSON error from the failed network request.
The mapper is not created.

Steps to Reproduce

Create a new Realm.
Create a new Client with the following settings:

Client authentication: ON
Authorization: OFF
Authentication flow: Standard flow only
Service accounts roles: ON

Navigate to the Client scopes tab for the new client.
Click on the dedicated scope (e.g., my-client-dedicated).
Go to the Mappers tab.
Click Configure a new mapper.
Select the Audience mapper type.
Fill in the form:

Name: my-client-audience
Included Client Audience: Select the client itself (my-client) from the dropdown.
Add to ID token: ON

Click Save.
The unknown_error popup appears.

What I've Tried

Using different browsers
Clearing browser cache
Completely deleting and recreating the client from scratch
Restarting the Keycloak and database containers

Workaround

I was able to successfully create the mapper using the Admin REST API directly,
which suggests a potential bug in the UI.

Question

Has anyone else encountered this?
Is there a known issue or a better workaround for the UI?

Answered by mabartos

Aug 3, 2026

Created #51384

View full answer

davidtrevor97 · 2025-10-23T08:40:29Z

davidtrevor97
Oct 23, 2025

Had the same issue today, still didn't found a solution

1 reply

Ritikkumar352 Oct 23, 2025
Author

Hi David, I had pause the key cloak integration with my app for few weeks, till then if you find the solution please let me know.
Thanks

IvanTarjan · 2026-04-14T18:15:43Z

IvanTarjan
Apr 14, 2026

Hello, I'm also having this issue, did anyone find a solution?

1 reply

Ritikkumar352 Aug 2, 2026
Author

Hey, Ivan Did you get the solution?

mabartos · 2026-08-03T07:45:22Z

mabartos
Aug 3, 2026
Collaborator

Created #51384

0 replies

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Keycloak UI Error: unknown_error / Cannot parse the JSON when Adding Audience Mapper #42784

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Keycloak UI Error: unknown_error / Cannot parse the JSON when Adding Audience Mapper #42784

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Ritikkumar352 Sep 20, 2025

Keycloak UI Error: unknown_error / Cannot parse the JSON when Adding Audience Mapper

Environment

Goal

Expected Behavior

Actual Behavior

Steps to Reproduce

What I've Tried

Workaround

Question

Replies: 3 comments · 2 replies

Uh oh!

davidtrevor97 Oct 23, 2025

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Ritikkumar352 Oct 23, 2025 Author

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IvanTarjan Apr 14, 2026

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Ritikkumar352 Aug 2, 2026 Author

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mabartos Aug 3, 2026 Collaborator

Ritikkumar352
Sep 20, 2025

Keycloak UI Error: `unknown_error` / Cannot parse the JSON when Adding Audience Mapper

Replies: 3 comments 2 replies

davidtrevor97
Oct 23, 2025

Ritikkumar352 Oct 23, 2025
Author

IvanTarjan
Apr 14, 2026

Ritikkumar352 Aug 2, 2026
Author

mabartos
Aug 3, 2026
Collaborator