CoreJSON

AI JSON Generator

This AI JSON generator lets you describe the data you need in plain language instead of writing large JSON by hand, and an LLM produces standard JSON for you. It supports your own API key (BYOK): every request goes directly from your browser to the model provider and never passes through this site, which suits sensitive data.

Open in the workbench Runs locally · nothing is uploaded

How to use it

  1. 1

    Configure your API key

    Open "Model settings" and enter your OpenAI or compatible-platform API key. The key is stored only in your browser and is never uploaded by this site.

  2. 2

    Describe what you need

    In the input box, describe the data in natural language — for example "generate an array of 5 users with a name, a random age and an email".

  3. 3

    Generate the data

    Click "Generate" and the AI returns the JSON on the right, automatically pretty-printed and validated.

  4. 4

    Keep working with it

    Send the generated JSON straight to the formatter workspace or copy it for use elsewhere.

Key features

Natural language to data

Describe the structure and field requirements and get mock data or a config template, saving you from writing large JSON by hand.

BYOK (bring your own key)

You provide your own API key and model requests go directly from your browser, which is suitable for handling sensitive data.

Automatic formatting and validation

The AI output is parsed and formatted automatically to make sure the resulting JSON is structurally valid.

Non-JSON noise is stripped

If the model wraps its answer in Markdown fences or adds commentary, the tool extracts the valid JSON portion before formatting.

Wired into the toolchain

Generated JSON can flow to other tools (convert to entities, diff, tree view) without manual copy-paste.

OpenAI, Anthropic or compatible

Use the official OpenAI or Anthropic endpoints, or any OpenAI-compatible provider by supplying the full endpoint URL. The request is sent from the browser, so the endpoint must allow CORS.

Common errors & troubleshooting

  • ! The more specific the description, the closer the JSON. Spell out field names, types and whether a field must follow a particular format.
  • ! If the result misses the mark, add a constraint such as "output only valid JSON with no extra explanation" to the description.
  • ! To use an OpenAI-compatible provider, choose "Custom (OpenAI compatible)" in settings and enter the full endpoint URL (like https://.../v1/chat/completions).
  • ! The request is issued directly by the browser, so a third-party endpoint must support cross-origin (CORS) requests, otherwise the connection fails.

Frequently asked questions

Will the generated JSON include extra prose?

The underlying prompt already asks the model to output JSON only, but an LLM may still add some Markdown. The tool automatically extracts the valid JSON part and formats it.

Is my API key stored on your servers?

No. In BYOK mode the API key is kept only in your browser LocalStorage, and all AI requests are issued directly by your browser to the model provider (such as OpenAI). This site has no backend.

Which AI models are supported?

The official OpenAI and Anthropic endpoints, plus any third-party provider that follows the OpenAI API format (configure the full endpoint URL). Note that requests are made from the browser, so third-party endpoints must support CORS or the connection will fail.

Is anything sent through this site?

No. Requests go straight from your browser to the model provider you configure; this site never receives your prompt or your key, so there is no server-side copy of either.

Related tools

JSON Formatter

Format, beautify and validate JSON in your browser. Errors point to the exact line and column, and you can indent with 2 spaces, 4 spaces or a tab.

JSON Tree Viewer

Render JSON as a collapsible tree with colour-coded types, search with ancestor expansion, JSONPath breadcrumbs, inline editing and windowed rendering for huge files.

JSON to TypeScript

Generate TypeScript interface or type definitions from a sample JSON payload.

JSON Schema to JSON

Generate example data from a JSON Schema. Supports const / enum / default / examples, local $ref (definitions / $defs), allOf / oneOf / anyOf and semantic format placeholders such as email, date-time and UUID.