Request headers in Postman - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are request headers in an HTTP request?

Request headers are extra pieces of information sent with an HTTP request. They tell the server details like the type of data the client can accept, the language preference, or authentication tokens.

beginner

Why do we use the Content-Type header in a request?

The Content-Type header tells the server what kind of data is being sent in the request body, like JSON, XML, or form data. This helps the server understand how to read the data.

intermediate

How does the Authorization header work in requests?

The Authorization header carries credentials like tokens or passwords to prove the client has permission to access the server's resources.

beginner

In Postman, how can you add a custom request header?

In Postman, you go to the 'Headers' tab of your request, then add a new key-value pair for your custom header. For example, key: X-Custom-Header, value: 12345.

intermediate

What happens if you send a request without the Accept header?

If the Accept header is missing, the server may respond with its default data format. This might not be what the client expects, so it’s good to specify it.

Which header tells the server what format the client expects in response?

A Accept

B User-Agent

C Authorization

D Content-Type

The Accept header specifies the media types the client can handle in the response.

In Postman, where do you add request headers?

A Headers tab

B Body tab

C Tests tab

D Pre-request Script tab

Request headers are added in the Headers tab of the Postman request.

What is the purpose of the Authorization header?

A To specify the data format sent

B To send credentials for access

C To tell the server the client’s language

D To identify the client software

Authorization header carries credentials like tokens or passwords to authenticate the client.

Which header is used to tell the server the type of data in the request body?

A Accept

B Cache-Control

C Authorization

D Content-Type

Content-Type header specifies the media type of the request body.

If you want to add a custom header in Postman, what should you do?

A Add it in the URL

B Add it in the Body tab

C Add it in the Headers tab as a key-value pair

D Add it in the Authorization tab

Custom headers are added as key-value pairs in the Headers tab.

Explain what request headers are and why they are important in API testing.

Think about how you tell a friend what kind of message you are sending.

Describe how to add and use request headers in Postman for testing an API.

Imagine you are sending a letter with extra notes attached.

Practice

1. What is the main purpose of request headers in Postman API calls?

easy

A. To send extra information like authentication or data format

B. To write the body content of the request

C. To specify the URL of the API endpoint

D. To display the response status code

Solution

1. Step 1: Understand what request headers do

   Request headers add extra info to the API call, such as authentication tokens or content type.

2. Step 2: Differentiate headers from other parts

   Headers are not the body or URL; they are key-value pairs sent with the request.

3. Final Answer:

   To send extra information like authentication or data format -> Option A

4. Quick Check:

   Request headers = extra info [OK]

Hint: Headers add info like auth or format, not body or URL [OK]

Common Mistakes:

• Confusing headers with request body
• Thinking headers specify the URL
• Assuming headers show response info

2. Which of the following is the correct way to add a header named Authorization with value Bearer token123 in Postman?

easy

A. Authorization -> Bearer token123

B. Authorization = Bearer token123

C. Authorization Bearer token123

D. Authorization: Bearer token123

Solution

1. Step 1: Recall header syntax in HTTP

   Headers use a colon ':' to separate key and value, like Key: Value.

2. Step 2: Match the correct syntax

   Authorization: Bearer token123 uses colon correctly; others use wrong separators or miss colon.

3. Final Answer:

   Authorization: Bearer token123 -> Option D

4. Quick Check:

   Headers use colon ':' between key and value [OK]

Hint: Headers use colon ':' between key and value [OK]

Common Mistakes:

• Using '=' instead of ':'
• Omitting colon separator
• Using arrows or spaces only

3. Given this Postman header setup:
Content-Type: application/json
Accept: application/xml
What will the server expect and respond with?

medium

A. Server expects XML data and responds with JSON

B. Server expects JSON data and responds with XML

C. Server expects and responds with JSON

D. Server expects and responds with XML

Solution

1. Step 1: Understand Content-Type header

   Content-Type tells the server the format of data sent by client; here it is JSON.

2. Step 2: Understand Accept header

   Accept tells the server what response format client wants; here it is XML.

3. Final Answer:

   Server expects JSON data and responds with XML -> Option B

4. Quick Check:

   Content-Type = sent format, Accept = response format [OK]

Hint: Content-Type = sent data, Accept = desired response [OK]

Common Mistakes:

• Mixing up Content-Type and Accept meanings
• Assuming both headers mean the same
• Ignoring Accept header

4. You added a header in Postman as Content-Type = application/json but the server returns a 415 Unsupported Media Type error. What is the likely problem?

medium

A. You forgot to add the Authorization header

B. The value 'application/json' is invalid

C. Header syntax is incorrect; should use colon ':' instead of '='

D. The server does not support JSON at all

Solution

1. Step 1: Check header syntax

   Headers must use colon ':' to separate key and value, not '='.

2. Step 2: Understand server error 415

   415 means server rejects media type due to wrong or missing Content-Type header.

3. Final Answer:

   Header syntax is incorrect; should use colon ':' instead of '=' -> Option C

4. Quick Check:

   Wrong header syntax causes 415 error [OK]

Hint: Use ':' not '=' in headers to avoid 415 error [OK]

Common Mistakes:

• Using '=' instead of ':' in headers
• Assuming server rejects JSON always
• Ignoring header syntax errors

5. You want to send a POST request with JSON data and an API key for authentication in Postman. Which header setup is correct?

hard

A. Content-Type: application/json and Authorization: ApiKey 12345

B. Accept: application/json and Authorization: 12345

C. Content-Type: text/plain and ApiKey: 12345

D. Authorization: Bearer 12345 only

Solution

1. Step 1: Identify correct content type for JSON data

   Use Content-Type: application/json to tell server data format sent is JSON.

2. Step 2: Use proper authorization header format

   API keys often use Authorization: ApiKey [key] or similar; here Authorization: ApiKey 12345 is correct.

3. Final Answer:

   Content-Type: application/json and Authorization: ApiKey 12345 -> Option A

4. Quick Check:

   Content-Type + Authorization with correct syntax [OK]

Hint: Use Content-Type for data and Authorization for API key [OK]

Common Mistakes:

• Using wrong Content-Type for JSON
• Putting API key in wrong header
• Omitting Content-Type header