CJSON: Conversation JSON

Own Your Conversations

CJSON (Conversation JSON) is an open standard for portable conversation data across AI tools/applications.

With CJSON, you can:

  • Build editors, analyzers, and visualizers on top of a shared format.

  • Move your conversations between tools and providers without lock-in.

  • Ensure long-term ownership of your data.

Current Version

This documentation refers to version 0.1.0-SNAPSHOT of the schema.

What is CJSON?

CJSON defines a structured, vendor-neutral JSON schema for conversation data. Examples of what’s included:

  • Messages – text, media attachments, tool calls and execution metadata.

  • Metadata – timestamps, participants, context.

  • Extensions – define vendor-specific extensions to build on top of the schema.

  • Tool workflows – tool execution requests, approval blocks, and tool results.

  • Auditing – add audit trails to your conversations and messages.

A two-message example
{
  "schemaUrl": "https://schema.cjson.dev/0/conversation/cjson-0.1.0.schema.json",
  "conversationTitle": "Example Conversation",
  "id": "67589b87-e703-47db-8900-7533bad5465d",
  "mediaType": "application/vnd.cjson+json",
  "systemMessage": "You are an expert in helping solve problems.",
  "messages": [ {
    "id": "3355200c-cd27-4f81-96c9-7eaa96628f77",
    "role": "user",
    "messageType": "text",
    "content": "What is CJSON?"
  }, {
    "id": "5ae2a633-586e-4b0c-b6e6-25551728811c",
    "role": "assistant",
    "messageType": "composite",
    "contentBlocks": [ {
      "createdAt": "2025-09-18 15:01:19.950",
      "id": "830526cb-585a-4c39-8018-24830c5fd9cf",
      "text": "CJSON is an open standard for conversational data. It's a open JSON Schema.",
      "blockType": "text"
    } ]
  } ],
  "modelId": "8543f7f8-b260-4c76-b102-869096e5a4e0"
}

Why CJSON?

I’ve been developing AI tools as hobby projects for the last couple of months, and everytime I’d face the same set of questions around the data modeling for the conversation data.

In general, many AI tools that allow users to create chats/conversations with AI models tend to share a similar subset of elements. For example:

  • The definition of the AI models that the user wants to use/connect to

  • The way the conversations are presented to the user, and

  • The definition of the tools (MCP or not) that the user wants to provide to the models.

I wanted to have a data model that would allow developers to build on-top of a shared standard and that would be portable and transparent. And wanted to be able to see my conversation data in both a web interface and an IDE – there is no reason this shouldn’t be possible! Except that, I can’t easily export my conversation data from one tool to the other 😅 (at least, not yet!).

CJSON started from all of the above.

It’s in early versions. Input from other use cases or even from using it is more than welcome such that, with time, it can grow into a more robust and complete spec.

  • Portability :: Export/import your conversations with ease.

  • Transparency :: Know exactly what data is stored and shared.

  • Ecosystem :: Build tools once, work with many providers.