Working with JSON is a daily activity for most developers, and having the right tools significantly reduces the time spent navigating, validating, and transforming JSON data. This guide covers the best JSON tools across different categories - browser-based utilities, command-line tools, code editor extensions, and API clients - with practical advice on when to reach for each one.

Category 1: JSON Formatters and Pretty Printers

Raw JSON from an API is often minified (single line, no whitespace) making it unreadable. Formatters add indentation and line breaks to make the structure visible.

Browser Developer Tools

The quickest way to format a JSON API response is already built into your browser. In Chrome or Firefox DevTools:

  1. Open the Network tab
  2. Click on a request that returns JSON
  3. Click the "Preview" or "Response" tab - the browser auto-formats it

For Chrome, the "Preview" tab renders JSON as a collapsible tree. This is the fastest option for API responses you can see in the network tab.

Code Editor Built-in Formatters

VS Code formats JSON files automatically. Open a .json file and press Shift+Alt+F (Windows/Linux) or Shift+Option+F (Mac) to format. This uses the built-in JSON language server and respects your indentation settings.

Category 2: JSON Key Extractors

When exploring an unfamiliar API response, you need to quickly understand what fields are available - especially when the response has deeply nested objects and arrays.

JSON Keyper

JSON Keyper extracts every key path from a JSON document, including nested objects and array indices. The output is a flat list like user.address.city and items[0].product.name - perfect for understanding the full structure before writing any code. It works in your browser with no login or installation required.

Best for: quickly mapping an API response structure, creating field mappings for ETL, documenting a JSON schema

jq (Command Line)

jq is a Swiss Army knife for JSON on the command line. Extract all key paths with:

# All paths as dot-notation strings
jq '[paths | join(".")]' data.json

# All top-level keys
jq 'keys' data.json

# Pretty print
jq '.' data.json

# Extract specific nested value
jq '.user.address.city' data.json

# Filter array elements
jq '.orders[] | select(.status == "shipped")' data.json

Best for: shell scripts, CI/CD pipelines, transforming large JSON files, one-liners

Category 3: JSON Validators

A JSON validator tells you whether a string is valid JSON and, if not, where the syntax error is.

Browser Console

The quickest validator available: open DevTools (F12), go to the Console tab, and type:

JSON.parse(`YOUR JSON HERE`);

If it throws a SyntaxError, the error message usually tells you exactly what is wrong and at which position.

VS Code

Any file saved with a .json extension gets automatic JSON validation. Errors show as red underlines with detailed messages in the Problems panel.

JSON Schema Validation

For validating that JSON conforms to a specific schema (not just that it is valid JSON), use:

  • Ajv - the fastest JavaScript JSON Schema validator, supports all draft versions
  • jsonschema - the standard Python JSON Schema validator
  • Hyperjump - a modern JavaScript validator with full JSON Schema 2020-12 support

Category 4: API Clients

API clients let you send HTTP requests to REST APIs and inspect the JSON responses interactively.

Postman

Postman is the most popular GUI API client. Features relevant to JSON work:

  • Pretty-prints JSON responses automatically
  • Lets you set Content-Type: application/json and write JSON request bodies with syntax highlighting
  • Allows saving requests in collections for reuse
  • Built-in test scripting to validate JSON responses
  • Environment variables for switching between dev/staging/prod

Insomnia

Insomnia is an open-source alternative to Postman with a cleaner UI. Particularly good for GraphQL queries. Also supports gRPC and WebSocket testing.

HTTPie

HTTPie is a command-line HTTP client with JSON output by default:

# GET request - pretty-printed JSON response automatically
http GET api.example.com/users/1

# POST with JSON body
http POST api.example.com/users name="Alice" email="alice@example.com"

# With authentication
http GET api.example.com/users/1 Authorization:"Bearer token"

# Save response to file
http GET api.example.com/data > response.json

curl

curl is available everywhere and useful for scripting, but its output is not JSON-formatted by default. Pipe to jq for readability:

curl -s https://api.example.com/users/1 | jq '.'

Category 5: JSON Diff Tools

When debugging API changes or comparing configurations, you need to see exactly what changed between two JSON documents.

jq for Diffing

# Sort both files and diff them
diff <(jq -S . file1.json) <(jq -S . file2.json)

The -S flag sorts keys, ensuring that key order differences do not show up as false positives.

VS Code Diff

In VS Code: right-click a file in the Explorer and choose "Select for Compare", then right-click the second file and "Compare with Selected". Works for JSON files out of the box.

Category 6: Code Editor Extensions for JSON

Several VS Code extensions significantly improve the JSON development experience:

  • Paste JSON as Code - paste JSON and generate TypeScript interfaces, Python classes, or Go structs automatically
  • JSON to TypeScript - similar to above, focused on TypeScript type generation
  • REST Client - make HTTP requests directly from a .http file in VS Code, with JSON response formatting
  • JSONPath IntelliSense - autocomplete for JSONPath expressions

Category 7: JSON Transformation Libraries

When you need to transform, filter, or reshape JSON data programmatically in production code:

  • jq (any language) - use it as a command-line step in data pipelines
  • jmespath (JavaScript, Python) - JMESPath query language for extracting and transforming JSON
  • jsonata (JavaScript) - powerful transformation language with arithmetic, string functions, and aggregations
  • Ajv (JavaScript) - fast JSON Schema validation
  • lodash.get (JavaScript) - safe nested property access with a path string like _.get(obj, 'user.address.city')

Choosing the Right Tool

TaskBest Tool
Understand a new API's response structureJSON Keyper
Pretty-print API response in terminaljq or HTTPie
Validate JSON syntax quicklyBrowser console / VS Code
Validate against a schemaAjv (JS) or jsonschema (Python)
Explore and test API endpointsPostman or Insomnia
Diff two JSON filesjq + diff or VS Code diff
Transform JSON in a pipelinejq or jmespath
Generate TypeScript types from JSONPaste JSON as Code (VS Code)

Map Any JSON Structure Instantly

JSON Keyper is purpose-built for one task: extracting every key path from a JSON document so you can understand its structure without manual exploration.

Open JSON Keyper