HEAD and OPTIONS methods in Rest API - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this HEAD request?

Given a REST API endpoint that returns the following response for a GET request:

Status: 200 OK
Headers: Content-Type: application/json
Body: {"message": "Hello"}

What will be the response body when a HEAD request is made to the same endpoint?

A Body: empty

B Body: {"message": "Hello"}

C Body: null

D Body: "HEAD request not supported"

💡 Hint

Remember, HEAD requests return headers only, no body.

The HEAD method returns the same headers as GET but does not return a message body. So the body is empty.

❓ Predict Output

intermediate

What headers does an OPTIONS request return?

An OPTIONS request is sent to a REST API endpoint. Which header is expected in the response to indicate allowed methods?

A Cache-Control: no-cache

B Content-Type: application/json

C Allow: GET, POST, OPTIONS

D Authorization: Bearer token

💡 Hint

OPTIONS tells the client what methods are allowed on the resource.

The Allow header lists HTTP methods supported by the resource, returned in response to OPTIONS requests.

🧠 Conceptual

advanced

Why use HEAD instead of GET?

Which is the main reason to use the HEAD method instead of GET in REST APIs?

A To retrieve only headers without the response body, saving bandwidth

B To update a resource partially

C To delete a resource

D To create a new resource

💡 Hint

Think about checking resource metadata without downloading the content.

HEAD requests return headers only, useful to check metadata or existence without downloading the body.

❓ Predict Output

advanced

What error occurs if OPTIONS is not supported?

If a client sends an OPTIONS request to a REST API endpoint that does not support OPTIONS, what is the typical HTTP status code returned?

A 404 Not Found

B 405 Method Not Allowed

C 500 Internal Server Error

D 200 OK

💡 Hint

Think about what happens when a method is not allowed on a resource.

405 indicates the method is not allowed on the resource, which applies if OPTIONS is unsupported.

🧠 Conceptual

expert

How do HEAD and OPTIONS improve REST API efficiency?

Which statement best explains how HEAD and OPTIONS methods help improve REST API efficiency?

A HEAD creates new resources; OPTIONS modifies existing resources

B HEAD caches responses automatically; OPTIONS encrypts data for security

C HEAD updates resource metadata; OPTIONS deletes unused resources

D HEAD reduces data transfer by sending headers only; OPTIONS informs clients of allowed methods without extra requests

💡 Hint

Consider how these methods reduce unnecessary data and requests.

HEAD avoids sending body data when only headers are needed; OPTIONS lets clients know allowed methods to avoid trial-and-error requests.

Practice

1. What is the primary purpose of the HEAD method in REST APIs?

easy

A. To create a new resource on the server

B. To delete a resource from the server

C. To update a resource partially

D. To retrieve only the headers of a resource without the body

Solution

1. Step 1: Understand the HEAD method role

   The HEAD method requests headers only, not the full content.

2. Step 2: Compare with other methods

   Unlike GET, it does not return the body, only metadata.

3. Final Answer:

   To retrieve only the headers of a resource without the body -> Option D

4. Quick Check:

   HEAD returns headers only [OK]

Hint: HEAD fetches headers only, no content body [OK]

Common Mistakes:

• Confusing HEAD with GET which returns full content
• Thinking HEAD modifies data on server
• Assuming HEAD returns body content

2. Which of the following is the correct syntax to send an OPTIONS request using curl?

easy

A. curl -X POST https://api.example.com/resource

B. curl -X HEAD https://api.example.com/resource

C. curl -X OPTIONS https://api.example.com/resource

D. curl --get https://api.example.com/resource

Solution

1. Step 1: Identify the method flag in curl

   The -X option specifies the HTTP method to use.

2. Step 2: Match the method to the question

   To send an OPTIONS request, use -X OPTIONS.

3. Final Answer:

   curl -X OPTIONS https://api.example.com/resource -> Option C

4. Quick Check:

   curl -X OPTIONS sends OPTIONS request [OK]

Hint: Use curl -X OPTIONS to send OPTIONS request [OK]

Common Mistakes:

• Using -X HEAD instead of OPTIONS
• Using --get which sends GET request
• Using POST method incorrectly

3. Given the following HTTP response headers from an OPTIONS request:

Allow: GET, POST, OPTIONS, HEAD

What does this header tell the client?

medium

A. The server supports only GET and POST methods

B. The server supports GET, POST, OPTIONS, and HEAD methods on this resource

C. The server denies all methods except OPTIONS

D. The server supports DELETE and PUT methods

Solution

1. Step 1: Read the Allow header

   The Allow header lists HTTP methods the server supports for the resource.

2. Step 2: Interpret the methods listed

   It shows GET, POST, OPTIONS, and HEAD are allowed methods.

3. Final Answer:

   The server supports GET, POST, OPTIONS, and HEAD methods on this resource -> Option B

4. Quick Check:

   Allow header lists supported methods [OK]

Hint: Allow header shows all supported methods [OK]

Common Mistakes:

• Ignoring OPTIONS and HEAD in the list
• Assuming only GET and POST are allowed
• Confusing Allow header with authentication

4. You wrote this code to handle HEAD requests in your REST API server:

if request.method == 'HEAD':
    return get_resource()

But clients receive the full content body. What is the problem?

medium

A. The code returns full content instead of headers only

B. The method name should be lowercase 'head'

C. HEAD requests must be redirected to GET method

D. The server must respond with status 201 for HEAD

Solution

1. Step 1: Analyze the code behavior

   The code calls get_resource() which returns full content including body.

2. Step 2: Understand HEAD response requirements

   HEAD must return headers only, no body content.

3. Final Answer:

   The code returns full content instead of headers only -> Option A

4. Quick Check:

   HEAD returns headers only, not full body [OK]

Hint: HEAD must not return body, only headers [OK]

Common Mistakes:

• Returning full content for HEAD requests
• Using wrong method name case
• Confusing HEAD with GET behavior

5. You want to optimize your REST API by using HEAD and OPTIONS methods. Which approach best improves client efficiency?

hard

A. Use HEAD to check resource existence and OPTIONS to discover allowed methods before sending requests

B. Use OPTIONS to fetch full resource data and HEAD to update resources

C. Use HEAD to delete resources and OPTIONS to create new ones

D. Ignore HEAD and OPTIONS and always use GET and POST

Solution

1. Step 1: Understand HEAD usage

   HEAD checks if a resource exists by fetching headers without body, saving bandwidth.

2. Step 2: Understand OPTIONS usage

   OPTIONS tells clients which HTTP methods are allowed, helping avoid invalid requests.

3. Step 3: Combine for efficiency

   Using both before heavy requests reduces unnecessary data transfer and errors.

4. Final Answer:

   Use HEAD to check resource existence and OPTIONS to discover allowed methods before sending requests -> Option A

5. Quick Check:

   HEAD checks headers, OPTIONS lists methods [OK]

Hint: HEAD checks existence, OPTIONS lists allowed methods [OK]

Common Mistakes:

• Using OPTIONS to fetch full data (wrong)
• Using HEAD to modify resources (wrong)
• Ignoring these methods and wasting bandwidth