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JSON Formatter
API Guides8 min read

How APIs use JSON for data exchange

From REST payloads to GraphQL responses and webhooks, JSON is the lingua franca of modern APIs. Here's how it works in practice.

By JSON Formatter Team

Why APIs standardized on JSON

Modern web APIs almost universally speak JSON. It's the smallest common denominator that every language parses out of the box, it maps cleanly to native types, and it's readable during debugging without special tooling.

If you've ever curled an endpoint and squinted at the response, you've already used a JSON API. Tools like our JSON Formatter exist to make that squinting go away.

REST + JSON

A REST endpoint typically accepts and returns JSON with a Content-Type: application/json header. Every field is a JSON primitive — string, number, boolean, null, array or object. Timestamps are ISO-8601 strings because JSON has no date type.

GraphQL + JSON

GraphQL uses JSON for both the request envelope and the response, even though the query itself is written in GraphQL syntax. The response always has a data key and optionally an errors array. Because GraphQL responses are just JSON, our JSON Viewer and Tree Viewer work on them unchanged.

Webhooks

Third-party webhooks (Stripe, GitHub, Slack) POST JSON to your endpoint. When one fires and you're confused about the shape, paste the raw body into the formatter and click Beautify — you'll see the structure immediately.

Debugging API responses

Three tools cover 90% of API debugging:

1. JSON Formatter — turn a wall of text into readable indentation. 2. JSON Validator — locate the exact byte where parsing broke. 3. JSON Compare — diff a working response against a broken one.

Best practices when designing a JSON API

  • Use consistent casing. snake_case or camelCase — pick one per API and stick to it.
  • Return arrays, not objects with numeric keys.
  • Nest sensibly. Deep nesting kills client ergonomics.
  • Use ISO-8601 for dates. Sortable and unambiguous.
  • Include an errors array on failures.
  • Version your API. Breaking JSON changes without a version bump breaks every client.

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