Attach a schema to a topic

What you'll achieve

A data contract (schema) attached to a topic, so every application writing to it agrees on what the data looks like.

Before you start

• The topic already exists — schemas are always created from a topic's page, never on their own. (Need one? Create a topic first.)
• Your role badge says Developer or higher and the environment allows changes (in a read-only environment only admins can do this) — otherwise the topic page shows "Contact an admin to create a data contract" instead of a button.
• You have the schema text (usually provided by the team building the application), or you start from the built-in sample.

Steps

1. Click Topics in the sidebar, open your topic, and go to the Data contract tab.
2. Choose Value (the message content — the usual choice) or Key (the message's identifier) with the toggle at the top of the tab.
3. Click Create data contract.
4. On the form, pick the Type: Avro (default), JSON Schema, or Protobuf — whichever the application team told you to use. The name is chosen for you: the topic name plus -value or -key.
5. Replace the sample in the Data Contract editor with your schema text. Use the Validate JSON button above the editor to check it — you want the green "Valid JSON".
6. Click Create Data Contract.

What success looks like

You land back on the Topics list. Open the topic's Data contract tab again and the schema is shown; it also now appears in the Schemas list in the sidebar.

Something went wrong?

• A red "Invalid JSON: …" box — the schema text has a typo; fix it and validate again.
• A "Topic Required" warning — you opened the create form directly instead of from a topic's Data contract tab; go back to step 1.
• No Create data contract button, just "Contact an admin to create a data contract" — you don't have edit rights here; ask your team's admin.

Background — schema types, naming, and compatibility rules? Read the Schemas guide.