API Testing & Mock Data Workbench
Build API request collections, import OpenAPI definitions, inspect and compare responses, generate mock JSON and check supported schema constraints in your browser.
Live requests contact the URL directly. CORS must be allowed by that API. Cookies are omitted.
Browser-controlled headers such as Host and Cookie cannot be set freely.
Use short-lived test credentials. No automatic storage.
Common constraints only. Unsupported constraints are reported for manual review.
Response & sandbox
No response yetNo baseline pinned
Response headers
No headers
Recent runs · this session
Try the offline demo, or create a request.
Using API Testing & Mock Data Workbench
Build API request collections, import OpenAPI definitions, inspect and compare responses, generate mock JSON and check supported schema constraints in your browser.
- Try the offline demo or import an OpenAPI 3 JSON/YAML definition. Select a request and replace any path placeholders.
- Set query parameters, headers, body and optional bearer authentication. Use variables such as {{baseUrl}}. Send only to APIs you intend to contact.
- Inspect the response, pin a comparison baseline and check your schema. Generate mock payloads or download your request collection.
Example
Load the offline example, generate mock JSON, then pin a baseline and edit the JSON to compare changes. No live request is needed for this workflow.
Questions & answers
Does this use a proxy server?
No. Live requests go directly from your browser to the entered API. Its server must permit CORS. Browser mixed-content, private-network and forbidden-header restrictions still apply.
Can I test without an API?
Yes. The offline demo, mock generation, JSON inspection, comparison and supported schema checks work locally. Mock JSON is a downloadable example, not a hosted endpoint.
Which OpenAPI files are supported?
OpenAPI 3.x JSON and YAML with local references, JSON request bodies and JSON 200/201/default response schemas. External or recursive references, multipart bodies and automatic OAuth flows are not supported. Review imported placeholders and schema constraints.
Is schema validation complete?
No. The tool checks common type, required, enum, const, object, array, length, range and composition constraints. Patterns, formats and other listed unsupported keywords produce review findings. Passing these checks is not full JSON Schema certification.
Are credentials saved?
Bearer tokens and common authentication headers are excluded from collection exports by default. An explicit export option includes them. Custom secrets in URLs, bodies, notes or unusually named headers must be removed manually. There is no automatic browser storage.
Why did my request fail?
CORS, connectivity, TLS, mixed-content and browser restrictions can appear as the same fetch failure. Check the API documentation and browser network panel; this tool cannot bypass these restrictions.
How large can responses be?
Displayed responses are limited to 5 MiB, with a configurable 1–120 second timeout. At most 20 response runs and 500 requests are retained in memory. Uploaded definitions and collections are limited to 5 MiB.
What does comparison include?
JSON comparisons show changed paths up to 300 differences. Non-JSON comparisons report whether the text changed. Status and timing are visible in history; a pinned baseline stays in memory until replaced or the page closes.
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