How to Test POST Requests Online with Custom Headers, Cookies, and JSON Body

Understanding the Anatomy of an HTTP POST Request

An HTTP POST request transmits structured information from a client to an API server to create or update resources. Testing POST requests requires configuring three vital components: the target URL with query parameters, request headers specifying authorization and formats, and the raw payload body.

Configuring Headers and Authentication

Headers dictate how a remote server receives and validates your request. When executing a POST request in an online API client, you typically provide:

• Content-Type: application/json: Tells the server to interpret the transmitted body as a structured JSON object.
• Authorization: Bearer <token>: Passes a JWT, OAuth access token, or personal developer key to authenticate the request.
• Accept: application/json: Informs the upstream server that your client expects a JSON-formatted response.

Sending JSON and Multipart Form-Data Payloads

Apier makes it simple to toggle between different payload modes depending on the endpoint requirements:

• Raw JSON: Validate and send nested objects, arrays, integers, and boolean parameters directly. The response inspector automatically renders Pretty, Raw, and Tree views for effortless parsing.
• Multipart Form-Data: Essential when testing endpoints that accept file uploads alongside metadata fields, such as profile picture uploads, PDF uploads, or document verification services.

Handling Cookies Automatically Across Successive Requests

When testing session-based APIs, the server responds with a Set-Cookie header containing session IDs or authentication cookies. Apier features a built-in domain-scoped cookie jar that automatically parses incoming cookies and attaches them to future requests sent to that domain, saving developers from manually copying and pasting cookie strings.