OpenAPI Formatter Online — Beautify JSON & YAML Specs

Pretty-print OpenAPI 3.0–3.2 documents (JSON or YAML) in your browser — 2 or 4 space indent, nothing uploaded.

Options

Indent

Sort keys

Pretty-print only — YAML comments are dropped on round-trip; JSON/YAML kind is preserved.

Use validate OpenAPI for OpenAPI 3.x schema conformance checks.

Format results

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Paste an OpenAPI document or click Format — formatted output appears when the run completes.

OpenAPI document

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Formatted output

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Formatting runs in your browser — nothing is uploaded.

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Format OpenAPI documentation

Pretty-print OpenAPI JSON or YAML in the browser.

Developer notes

• Generic pretty-print (JSON.stringify / yaml.dump) — optional recursive key sort for stable diffs. • Input kind is preserved: JSON in → JSON out; YAML in → YAML out. • Auto-format on paste/upload/sample; manual edits use the Format button (⌘↵). • YAML comments are lost on format. • Numeric openapi versions in YAML (e.g. 3.0) are normalized to strings (3.0.0). • Max input 512 KiB.

Options

Indent

Spaces per level for JSON.stringify / yaml.dump (2 or 4).

Sort keys

Off by default (preserves key order). On recursively sorts object keys for stable PR diffs; array element order is unchanged.

Use cases

• Clean up minified or hand-edited OpenAPI JSON/YAML before review. • Normalize indentation (2 or 4 spaces) for PR diffs. • Pair with Validate OpenAPI after formatting.

Examples

Compact JSON → indented

Before

{"openapi":"3.1.0","info":{"title":"Pets API","version":"1.0.0","description":"Simple pet store API"},"paths":{"/pets":{"get":{"operationId":"listPets","tags":["pets"],"summary":"List pets","parameters":[{"name":"limit","in":"query","schema":{"type":"integer"}}],"responses":{"200":{"description":"OK","content":{"application/json":{"schema":{"type":"array","items":{"$ref":"#/components/schemas/Pet"}}}}}}}}},"components":{"schemas":{"Pet":{"type":"object","required":["id","name"],"properties":{"id":{"type":"integer"},"name":{"type":"string"}}}}}}

After

{
  "openapi": "3.1.0",
  "info": {
    "title": "Pets API",
    "version": "1.0.0",
    "description": "Simple pet store API"
  },
  "paths": {
    "/pets": {
      "get": {
        "operationId": "listPets",
        "tags": [
          "pets"
        ],
        "summary": "List pets",
        "parameters": [
          {
            "name": "limit",
            "in": "query",
            "schema": {
              "type": "integer"
            }
          }
        ],
        "responses": {
          "200": {
            "description": "OK",
            "content": {
              "application/json": {
                "schema": {
                  "type": "array",
                  "items": {
                    "$ref": "#/components/schemas/Pet"
                  }
                }
              }
            }
          }
        }
      }
    }
  },
  "components": {
    "schemas": {
      "Pet": {
        "type": "object",
        "required": [
          "id",
          "name"
        ],
        "properties": {
          "id": {
            "type": "integer"
          },
          "name": {
            "type": "string"
          }
        }
      }
    }
  }
}

YAML preserved as YAML

Before

openapi: "3.0.3"
info:
  title: Pets
  version: 1.0.0
paths: {}

After

openapi: "3.0.3"
info:
  title: Pets
  version: 1.0.0
paths: {}

Format OpenAPI FAQ

Common questions

Does format preserve JSON vs YAML?

Yes. JSON input produces indented JSON; YAML input produces YAML via yaml.dump. Comments in YAML are not preserved.

Is this an OpenAPI-aware pretty printer?

Pretty-print is still generic (JSON.stringify / yaml.dump). Turn on Sort keys for recursive alphabetical key order (stable diffs). It is not an OpenAPI-aware reorder (paths before components, etc.).

What about openapi: 3.0 as a YAML number?

Numeric versions are normalized to strings (3 → 3.0.0, 3.0 → 3.0.0) before output.

Which OpenAPI versions?

OpenAPI 3.0, 3.1, and 3.2. Swagger 2.0 is not supported — use our OpenAPI tools only for 3.x.

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