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Getting Started
Everything you need to start using SchemaClient for API development, testing, and debugging.
- 01
Installation
Download and install the free SchemaClient API testing tool on Windows, macOS or Linux. No account needed to start sending requests.
- 02
Testing a REST API
A step-by-step guide to testing a REST API: choose a method, set headers and a body, send the request, and read the response properly.
- 03
Localhost tunneling
Give your local development server a public HTTPS URL in about a minute, and inspect every request that arrives through it.
- 04
Testing webhooks
Receive Stripe, GitHub or Slack webhooks on your development machine, inspect the payloads, and replay them without re-triggering the event.
- 05
Traffic monitoring
Watch every HTTP request flowing through your tunnel as it happens, filter down to the failures, and promote useful requests into a collection.
- 06
Schema validation
Define the shape a response is supposed to have, then check real responses against it so contract drift fails loudly instead of silently.
- 07
Collections & sync
Group related requests into collections, set shared base URLs and auth once, import from OpenAPI, and sync everything across your devices.
- 08
OpenAPI import
Turn an OpenAPI 3.x document into ready-to-send requests and response schemas in SchemaClient — and validate the live API against the contract it published.
- 09
Workspaces & teams
Share collections and schemas with your team using SchemaClient workspaces: role-based access, invite links that need no email setup, and conflict-safe sync.
- 10
GraphQL requests
Query GraphQL APIs in SchemaClient: switch a request to GQL mode, write the query and variables, and read the response — same collections and workflow as REST.
- 11
CLI (CI runner)
Run API collections and schema contract checks from the command line with @schemaclient/cli — a free CI collection runner, like Newman with schema validation.
- 12
WebSocket testing
Connect to ws:// and wss:// endpoints in SchemaClient, send JSON frames, follow the live message log, and validate frames in both directions against a schema.
- 13
SSE streams
Connect to any SSE endpoint in SchemaClient: watch events stream in live, resume with Last-Event-ID, and validate events against a schema by their event name.
- 14
gRPC calls
Call gRPC services without .proto files — SchemaClient discovers services via server reflection, sends requests as plain JSON, and shows real gRPC status codes.
- 15
Schema language reference
Complete reference for SchemaClient's schema language: types, constraint chains, named formats, and the @http, @graphql, @websocket, @sse and @grpc decorators.
- 16
CLI command reference
Every @schemaclient/cli command and flag: run, send, validate, schema lint/mock/infer — variables, reporters, data-driven runs, and the exit-code contract.
- 17
CLI collection format
The SchemaClient CLI collection format (.scoll.json): suite shape, expect assertions, captures, variables, data files, and the .tests.json sidecar.
- 18
Streaming through tunnels
Serve Server-Sent Events and chunked responses from localhost through a public tunnel URL — relayed live, chunk by chunk, with the timeouts you need to know.
Frequently asked questions
How do I test a REST API?
Open SchemaClient, enter your API endpoint URL, select the HTTP method (GET, POST, PUT, DELETE, PATCH), add headers and request body, then click Send. Inspect the API response including status code, headers, body, and response time. Save requests in collections for reuse.
How do I expose localhost to the internet?
Use SchemaClient's built-in localhost tunneling tool. Start your local server, go to the Tunnel tab, set your target URL (e.g., http://127.0.0.1:8000), click Start Tunnel, and get an instant public HTTPS URL. It's a free ngrok alternative with no signup restrictions.
How do I test webhooks locally?
Start a localhost tunnel in SchemaClient to get a public URL, use that URL as your webhook endpoint in services like Stripe, GitHub, or Slack, then watch incoming webhook requests in the real-time API traffic monitor. Inspect headers, payloads, and status codes instantly.
How do I validate API responses against a schema?
Go to the Schema tab in SchemaClient, create a new schema definition with expected fields and types, then validate API responses against it. SchemaClient also supports importing OpenAPI 3.x specs to auto-generate schemas.
Is SchemaClient a free Postman alternative?
Yes, SchemaClient is a free Postman and Insomnia alternative. It includes REST and GraphQL testing, localhost tunneling (which Postman doesn't have), real-time API monitoring, and schema validation — all included free. See the pricing page for plan details.
Looking for background rather than instructions? Read the blog.