JSON Key Extractor and Path Mapper

JSON Tools

Eight tools, one engine. Each runs entirely in your browser, and the JSON you have pasted comes with you when you switch between them.

A Worked Example

The quickest way to understand what the tool returns is to see one input mapped to each output format. Take this trimmed-down order response, the kind of payload you get back from a typical e-commerce API:

{
  "user": {
    "name": "Ada Lovelace",
    "address": { "city": "London", "country": { "code": "GB" } },
    "roles": ["admin", "engineer"]
  },
  "orders": [
    { "orderId": "ord_1001", "total": 249.99 },
    { "orderId": "ord_1002", "total": 15.50, "giftMessage": "Happy birthday" }
  ]
}

user
user.name
user.address
user.address.city
user.address.country
user.address.country.code
user.roles
orders
orders[0].orderId
orders[0].total
orders[1].orderId
orders[1].total
orders[1].giftMessage

user
user.name
user.address
user.address.city
user.address.country
user.address.country.code
user.roles
orders
orders[].orderId
orders[].total
orders[].giftMessage

user                        object
user.name                   string
user.address                object
user.address.city           string
user.address.country        object
user.address.country.code   string
user.roles                  array
orders                      array
orders[].orderId            string
orders[].total              number
orders[].giftMessage        string

interface Root {
  user: {
    name: string;
    address: {
      city: string;
      country: {
        code: string;
      };
    };
    roles: string[];
  };
  orders: {
    orderId: string;
    total: number;
    giftMessage?: string;
  }[];
}

Path Notation Reference

Different tools address the same nested value in different ways. This table maps a single field - the city inside the first order's shipping address - across the notations you are most likely to meet.

The one case that trips people up is a key that literally contains a dot. If your JSON has {"user.name": "Ada"}, then the dot-notation path user.name is ambiguous - it could equally describe a nested name inside a user object. Switch to the JSONPath output in that situation, which quotes the key as $['user.name'] and removes the ambiguity.

How to Use JSON Keyper

Which Output Format Should You Use?

Use Cases

Limitations Worth Knowing

No tool fits every job. These are the cases where JSON Keyper will not serve you well, and what to reach for instead:

• Very large files. The full path list is built in memory, so documents in the tens of megabytes may be slow or exhaust the tab. Use a streaming processor such as jq for those.
• Sample-based type inference. The TypeScript output describes the sample you pasted, not the API's real contract. A field that happens to be null in your sample is typed null, and a field absent from your sample cannot appear at all. Review the output against the API documentation.
• Numbers are all number. JSON does not distinguish integers from floats, so the type annotations cannot either.
• Keys containing dots. Dot-notation output is ambiguous for these. Switch to JSONPath, which quotes them.
• Not a validator. The tool checks that your JSON parses, but it does not check it against a JSON Schema. For that, see our guide to JSON Schema validation.
• Formatting does not sort keys or repair JSON. The formatted and minified outputs change whitespace only. They keep key order, and they report invalid JSON rather than guessing a fix.
• Live fetches are limited. The Execute cURL tab only reaches public http and https addresses on the standard ports, gives up after 5 seconds, and rejects responses over 2 MB. It cannot reach localhost or your internal network, and binary responses come back garbled. Any token or API key in the command passes through the proxy, so paste the response instead if that matters to you. For internal or slow APIs, run curl yourself and paste the output. The cURL runner page lists every supported option and limit.
• Not a store or host. JSON Keyper does not save your JSON or give it a URL. Everything is parsed in the browser and gone when you close the tab. If you need JSON hosted at a shareable endpoint, you want a JSON storage service, not this tool.

Frequently Asked Questions

Further Reading

Focused guides for a single output format, each with a worked example:

• JSON to TypeScript Interface Converter - how nested objects are inlined and optional fields detected.
• Flatten JSON to Dot Notation - collapsed vs expanded array indices, and when each view is the right one.
• JSONPath Expression Generator - wildcards, bracket notation, and how JSONPath differs from plain dot notation.
• JSON Tree Viewer - the structure as an indented outline, and why the tree always collapses array indices.
• Run a cURL Command Online - which curl options work, what the API receives through the proxy, and every limit.
• JSON Formatter - pretty-print or minify without changing a single value, and why most formatters cannot promise that.
• JSON Diff - compare two documents by value or structure, with breaking changes flagged and array items matched by ID.

Longer guides on working with JSON, written alongside this tool:

• How to Extract All Keys from a JSON Object - the same job done in JavaScript, Python, Ruby, and jq, with a comparison of when each is worth the effort.
• Understanding Nested JSON Objects and Arrays - safe access patterns for deeply nested data, and how to flatten a structure.
• Common JSON Structures in REST APIs - the envelope, pagination, and error shapes you will meet again and again.
• JSON Schema: A Practical Guide to Validating JSON - moving from "what keys are here" to "what keys are required".
• Working with JSON in Python - parsing, custom encoders, and streaming large files.
• Jackson vs Gson vs Moshi - choosing a JSON library on the JVM, and the unknown-property default that breaks services in production.
• Processing Large JSON Files - measured memory for jq and Python, and why plain jq is not a streaming tool.
• Why Your Browser Blocks API Calls - CORS, preflight requests, and what routing a request through a proxy actually costs.
• Browse all articles

Who Maintains JSON Keyper

Recent changes (full history in the changelog):

• September 30, 2026 - a cURL runner page, and curl commands now support -u, -G, --json, -b, and more, exactly as curl sends them.
• September 30, 2026 - JSON Diff: compare two documents by value or structure, with breaking changes flagged.
• September 29, 2026 - a new guide testing how Jackson, Pydantic, and Zod handle null, missing, and unknown fields, and a JSON formatter that never changes a value.

JSON Keyper has no accounts and no paywall. If it saves you time, you can support the project on GitHub Sponsors.

Found a document the tool handles wrongly? Tell me, or open an issue on GitHub.