What is an Endpoint?

An API Endpoint is the specific URL through which a client communicates with an API.

Each endpoint represents a particular resource or operation and is accessed using HTTP methods such as:

  • GET
  • POST
  • PUT
  • DELETE
  • PATCH

Endpoints can also include:

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  • Path parameters
  • Query parameters

Example

Retrieve user details using:

 
GET /users/{id}
 

Interview Tip:
"We followed RESTful naming conventions by using endpoints like /users instead of /getUsers, and we secured sensitive endpoints using authentication and authorization."

HTTP Request and Its Components

An HTTP Request is a message sent by the client to the server requesting an action or resource.

Components of an HTTP Request

HTTP Method

Specifies the operation to perform.

Examples:

  • GET
  • POST
  • PUT
  • PATCH
  • DELETE

URL (Endpoint)

The address of the API resource.

Example:

 
https://api.example.com/users
 

Headers

Contain metadata about the request.

Examples:

  • Authorization
  • Content-Type
  • Accept

Request Body (Optional)

Contains data sent to the server.

Typically used with:

  • POST
  • PUT
  • PATCH

Interview Tip:
"An HTTP request contains the HTTP method, endpoint URL, request headers, and an optional request body. We used Bearer Tokens for authentication and JSON payloads for sending request data."

HTTP Response and Its Components

An HTTP Response is the server's reply to an HTTP request.

Components of an HTTP Response

Status Code

Indicates whether the request was successful or failed.

Examples:

  • 200 OK
  • 201 Created
  • 400 Bad Request
  • 401 Unauthorized
  • 404 Not Found
  • 500 Internal Server Error

Headers

Provide metadata about the response.

Common headers include:

  • Content-Type
  • Cache-Control
  • CORS
  • Content-Length

Response Body (Optional)

Contains the actual data returned by the API.

Most REST APIs return JSON responses.

Interview Tip:
"We validated HTTP status codes, verified JSON response bodies, and checked important response headers such as Content-Type, Cache-Control, and CORS."

Request Headers

A Request Header is a key-value pair that provides additional information about an HTTP request.

Headers communicate metadata to the server.

Common Request Headers

Header Purpose
Authorization Sends authentication credentials
Content-Type Specifies the request payload format
Accept Specifies the expected response format
Cache-Control Controls request caching

Example

 
Authorization: Bearer <access_token>
Content-Type: application/json
 

During API testing, verify that:

  • Authentication headers are correct.
  • Content-Type matches the payload.
  • Required headers are present.

Interview Tip:
"We validated Authorization and Content-Type headers to ensure requests were authenticated correctly and payloads were sent in the expected format."

Request Body

The Request Body contains the data sent from the client to the server.

It is commonly used with:

  • POST
  • PUT
  • PATCH

Common Request Formats

  • JSON
  • XML
  • Form-data
  • x-www-form-urlencoded

Example

 
{
    "name": "John",
    "email": "john@example.com"
}
 

When testing request bodies, verify that:

  • Required fields are present.
  • Data types are correct.
  • Payload format is valid.
  • Business validation rules are followed.

Interview Tip:
"We ensured request payloads contained all mandatory fields and validated that the API correctly stored and returned the submitted data."

Response Body

A Response Body contains the data returned by the server after processing a request.

Most REST APIs return JSON responses.

Example

A successful request:

 
GET /users/101
 

may return:

 
{
    "id": 101,
    "name": "John",
    "email": "john@example.com"
}
 

When testing response bodies, verify:

  • Response structure.
  • Required fields.
  • Returned values.
  • JSON Schema.
  • Data types.

Interview Tip:
"We validated response bodies by checking returned values, verifying required fields, and performing JSON Schema validation in Postman."

Query Parameters

Query Parameters are optional key-value pairs appended to the URL to customize the API response.

They are commonly used for:

  • Filtering
  • Sorting
  • Searching
  • Pagination

Format

 
?key1=value1&key2=value2
 

Examples

Filter active users:

 
/users?status=active
 

Pagination:

 
/users?page=2&limit=10
 

Best Practices

  • Encode special characters properly.
  • Validate missing parameters.
  • Test invalid parameter values.
  • Verify default behavior.

Interview Tip:
"We tested query parameters using valid, invalid, and missing values to ensure filtering, pagination, and sorting behaved correctly."

Path Parameters

Path Parameters are dynamic values embedded directly within the endpoint URL.

They identify a specific resource.

In API documentation, they are represented using curly braces {}.

Example

 
/users/{id}
 

Actual request:

 
/users/123
 

Characteristics

  • Part of the URL path.
  • Usually mandatory.
  • Used to identify a specific resource.
  • Commonly used with GET, PUT, PATCH, and DELETE requests.

Interview Tip:
"While testing path parameters, we verified responses using valid IDs, invalid IDs, non-existing IDs, and missing values to ensure proper error handling."

Query Parameters vs Path Parameters

Aspect Query Parameters Path Parameters
Location After ? in the URL Inside the endpoint path
Format ?key=value /resource/{id}
Purpose Filter, sort, paginate, customize Identify a specific resource
Mandatory Usually optional Usually mandatory
Example /users?status=active&page=2 /users/123

Summary

  • Path Parameters identify a specific resource.
  • Query Parameters customize or filter the returned results.

FAQs

What is an endpoint in API testing?

An API endpoint is the specific URL through which clients communicate with an API. Each endpoint represents a particular resource or operation and is accessed using HTTP methods such as GET, POST, PUT, PATCH, or DELETE.

What are the key components of an HTTP request?

An HTTP request consists of:

  • HTTP method
  • URL (endpoint)
  • Request headers
  • Optional request body

What are the key components of an HTTP response?

An HTTP response consists of:

  • HTTP status code
  • Response headers
  • Optional response body

What is a request header?

A request header is a key-value pair that provides metadata about an HTTP request, including authentication, content type, accepted response format, caching information, and other request details.

What is a request body?

A request body contains the data sent from the client to the server, typically used in POST, PUT, and PATCH requests. It is commonly formatted as JSON, XML, or form-data.

What is the difference between Query Parameters and Path Parameters?

  • Path Parameters are part of the URL path and identify a specific resource (for example, /users/123). They are usually mandatory.
  • Query Parameters appear after the ? symbol and are used to filter, sort, search, or paginate results (for example, /users?status=active&page=2). They are generally optional.