Sylvaera / API Mock Generator
OPENAPI · GRAPHQL · POSTMAN · REST

Free API Mock Generator
Online

Paste any OpenAPI spec GraphQL schema URL or plain English — get realistic mock API responses with error codes pagination and auth headers. Export as JSON Postman or OpenAPI 3.0. Free no sign-up.

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Key features

Built for real workflows

📄
OpenAPI / Swagger
Paste any OpenAPI 2.0 or 3.0 spec and get realistic mock responses for every endpoint automatically.
◈
GraphQL Schema
Paste a GraphQL schema definition and get mock query and mutation responses with realistic data.
🔗
API URL
Paste a live API URL and Sylvaera infers the response structure to generate mocks.
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Plain English
Describe your API in plain English — 'a REST API for a food delivery app' — and get full mock responses.
How it works

Three steps, instant results

1
Upload or paste your data — supports CSV, JSON and plain text. Paste directly or upload a file from your computer.
2
Configure your options — select strategies, output format and any custom preferences from the clean interface.
3
Download your results — get processed data as CSV, JSON or Excel instantly. No waiting, no email required.
FAQ

Common questions

How do I generate mock API responses for free?

Paste an OpenAPI spec, GraphQL schema, URL or plain English at sylvaera.com/app and get realistic mock responses instantly. No sign-up.

Can I export as a Postman collection?

Yes. Export mock responses as Postman collections (.json) that import directly into Postman.

Does it include error responses?

Yes. Toggle to include 400, 401, 404, 500 and other error response examples alongside success responses.

Is this tool completely free?

Yes. No sign-up, no credit card, no usage limits for standard datasets. 100% free. All 7 Sylvaera tools are free.

Is my data safe?

Sylvaera does not store any uploaded data. All processing happens in-memory and is discarded immediately after your session ends.

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