HEAD and OPTIONS methods in Rest API - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the HTTP HEAD method do?

The HEAD method requests the headers that a GET request would get, but without the response body. It's like asking for the metadata only.

beginner

What is the purpose of the HTTP OPTIONS method?

OPTIONS asks the server which HTTP methods are allowed on a specific resource. It helps clients know what actions they can perform.

intermediate

How does the HEAD method help improve efficiency?

HEAD lets clients check resource information like size or modification date without downloading the whole content, saving bandwidth.

intermediate

When might a client use the OPTIONS method in real life?

A client might use OPTIONS before sending a request to check if the server supports methods like POST or DELETE on a resource, avoiding errors.

beginner

True or False: The response to a HEAD request contains a message body.

False. The HEAD response contains headers only, no message body.

What does the HEAD method return in its response?

A Headers and full body

B Only headers, no body

C Only body, no headers

D Nothing at all

HEAD returns only the headers, similar to GET but without the body.

Which HTTP method tells you what methods are allowed on a resource?

A GET

B POST

C OPTIONS

D HEAD

OPTIONS asks the server which HTTP methods are supported on a resource.

Why use HEAD instead of GET when checking a resource?

A To get metadata without downloading content

B To get the full content faster

C To delete the resource

D To update the resource

HEAD lets you get metadata like headers without downloading the full content.

If a server responds to OPTIONS with 'Allow: GET, POST', what does it mean?

A Only GET and POST methods are allowed on the resource

B All methods are allowed

C No methods are allowed

D The server is down

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

Can the HEAD method be used to check if a resource exists?

A Only if the resource is a file

B No, it cannot check existence

C Only with POST

D Yes, by checking the status code

HEAD returns status codes like GET, so you can check if a resource exists without downloading it.

Explain the difference between the HEAD and OPTIONS HTTP methods and give an example of when to use each.

Think about what information each method asks from the server.

Describe how the HEAD method can help save bandwidth in web applications.

Consider what happens when you only want to know if a file changed.

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