35 Best Http Interview Questions [2021 Updated]

Interview questions are always difficult to answer. The interviewer may ask you a question that you didn’t prepare for, or they may ask follow-up questions. It is important to have a set of responses and know how to answer any question that comes your way.

It is always good to have some questions in mind that you might want to ask the interviewer at the end of the interview, like what are some of their goals for the future? This will help you determine if this job would be a good fit for your skillset and personality.

1. What is HTTP?

Ans. Hypertext Transfer Protocol or HTTP is a major application of the internet that facilitates the requests and responses between web browsers and web servers.

HTTP is an application layer protocol, which means that it is built on top of other protocols such as TCP or UDP. It has been around since the 1990s and its latest revision was HTTP/2.

It is used to transfer data between two endpoints – a client and a server. It does not care about the content as long as it conforms to at least one of the formats it supports, such as HTML, XML, JSON, CSS, etc.

2. What are the basic features of HTTP?

Ans. There are three basic features of HTTP:

  1. Connectionless: In this the HTTP i.e. the browser makes a request and awaits a response. The server then processes the request and sends a response.
  2. Media Independent: Media Independent means any type of data can be sent across as long as both the client and the server can handle the content.
  3. Stateless: Since HTTP is connectionless, it is stateless too. In this feature, the client and server are aware of each other only during the request. Later, they lay forgotten.

3. Name the HTTP Request Methods

Ans. Although there are quite a few request methods, GET and POST are the common HTTP Request Methods. The other one’s being HEAD, PUT, DELETE, CONNECT, TRACE, PATCH and OPTIONS are the other request methods.

  1. GET: This request method is used to request or retrieve data from a specified resource. The GET method can only request data and not make any changes in it.
  2. HEAD: The HEAD method is almost identical to the GET method with the only difference being, GET method retrieves data while the HEAD method the header section of the data only.
  3. POST: The POST method is used for sending the data to the server and is included in the body of the server. It can also create a new resource and/or update an existing resource.
  4. PUT: The PUT method is used for replacing the current data of the target resource and uploading it with new content.
  5. DELETE: This method deletes the current data of the target resource which is provided by the URI.
  6. CONNECT: The CONNECT method is used for establishing a tunnel to the server provided by the URI.
  7. TRACE: This HTTP TRACE method performs a message loop-back test along the target resource path.
  8. PATCH: The PATCH method is a request method for making partial changes in the existing resource.
  9. OPTIONS: This method describes the available communication options for the target resource.

4. What is the Status Code in HTTP?

Ans. Status Code is a standard response code by the web server on the internet. It is the request made by the client to the server. This helps in identifying the reason due to which the web page is not responding or loading properly.

The status code is a three-digit number. The first digit of the status code is used to identify one of five answer classifications. The status code’s last two digits are not used for categorization.

5. What is URI?

Ans. Uniform Resource Identifier or URI is a sequence of characters that is used to identify something on the web. And the best-known type of URI is the Uniform Resource Locator (URL).

6. What are header fields in HTTP? And its types

Ans. Header Fields allow the client and server to pass information about the request and/or response message. There are four types of Header Fields:

  1. General Header: This header field is applicable to both request and response messages.
  2. Client Request Header: This field has applicability only for the request messages.
  3. Server Response Header: This is applicable only for the response messages.
  4. Entity-Header: This header field contains information about the body of the entity.

7. What is HTTP Response?

Ans. A server sends an HTTP response to the client. The response is used to offer the resource requested by the client. It’s also used to notify the client that the requested action has been completed. It can also notify the customer if there was a mistake in processing their request.

An HTTP response contains the following:

  • Status line
  • Response header fields
  • Message body

8. What are Idempotent methods?

Ans. If an identical request is made multiple times and the results have been the same, then this method is called Idempotent. And the PUT and DELETE methods are known as Idempotent Methods.

9. What are Safe Methods?

Ans. If HTTP methods do not change the state of the server, they are deemed safe. As a result, only read-only operations can be performed in safe ways. The HEAD, GET, OPTIONS, and TRACE methods are called Safe Methods because they only intend to retrieve the message and not change them.

10. What is the 409 HTTP response code?

Ans. When we make two PUT requests to generate the same resource, the server returns a 409 error to the browser.

11. What is Secure HTTP?

Ans. The secure HTTP protocol is a variant of HTTP that is encrypted. Data transfer over the World Wide Web is secure and encrypted using this protocol. It is used to carry out confidential internet operations such as bank/financial transactions.

12. The request took longer than expected” falls under which HTTP code?

Ans. It falls under the 408 Request Timeout response code.

13. What is the meaning of 500 Internal Server Error response HTTP code?

Ans. This code indicates that the server has encountered a problem and is unsure how to handle it.

14. What is HTTPS?

Ans. HTTPS stands for Hypertext Transfer Protocol Secure. It is the extended version of HTTP. This protocol is where the data is transferred via a secure connection such as Transport Layers Security.

15. Name and explain the different types of HTTP content negotiation

Ans. There are three types of HTTP content negotiation:

  1. Server-driven negotiation: Server-driven negotiation refers to the process of selecting the best response representation using a server-side algorithm. The response representations provided and the contents of specific header fields in the request message, as well as other information about the request, are used to make the decision.
  2. Agent-driven negotiation: After receiving an initial response from the origin server, and agent-driven negotiation ensues, in which the user agent selects the optimal representation for a response.
  3. Transparent negotiation: This negotiation is a combination of both server-driven and agent-driven negotiation.

16. What is DNS Spoofing?

Ans. DNS spoofing is a means of misleading a DNS server into giving an incorrect resolution.

The most common form of DNS spoofing is the use of the “ANY” record, which resolves to all addresses on a given network.

17. What is URI?

Ans. A Uniform Resource Identifier (URI) is a type of identifier that is used to identify either the source or destination of hypertext data.

A Uniform Resource Identifier (URI) is a type of identifier that is used to identify either the source or destination of hypertext data. This allows them to point directly towards any file on the internet.

18. What is REST?

Ans. REST, or Representational state transfer, is a form of API that allows for efficient hypermedia communication between two independent applications, such as a server and a client. It’s most commonly used for building APIs on top of existing resources which are then used to communicate to the client-side application.

REST can be used as an alternative to creating infrastructure-heavy RESTful APIs from scratch and can also act as a replacement for older technologies such as SOAP or XML-RPC because it uses fewer bytes on the wire than these other methods.

19. What is cURL?

Ans. cURL uses the C library libcurl for transferring files over a network.

cURL is free, open-source, and easy to use. It supports a range of internet protocols, including HTTP, HTTPS, FTP, MIME, and others. It can be used as a command-line program or through programming interfaces such as curl_easy_setopt() and curl_easy_perform().

20. What is a 500 internal server error?

Ans. This code is usually seen on a website that is most likely experiencing server overload.

The 500 error code usually appears when there are too many of the same requests to the server or if there is a spike in traffic.

This error message can also be generated when the server has run out of storage space, when the file has not been uploaded correctly, and due to hardware failure.

21. What is HTTP 201?

Ans. The 201 response code is one of the most popular codes on the internet. The HTTP status code 201 means that the request was successful and it is a response to a POST operation.

This is an indication that a new object has been created, such as a contact, or an order.

22. What is HTTP 409?

Ans. You can see the HTTP status code “HTTP/1.1 409 Conflict” in your browser when you are trying to access a page or document that has been taken down because it’s been duplicated elsewhere on the web.

23. What is an HTTP 405 error?

Ans. The 405 error is a server code that means that the requested resource is temporarily unavailable. It is most commonly seen when you try to access a site and it displays a message stating “this server could not fulfill the request.”

24. What is an HTTP 400 error?

Ans. 400 error is an HTTP status code. It means that the client’s request cannot be fulfilled because of something that lies on the client side.

The 400 error message is a response given by the server to notify the client about an unsuccessful request made by the client. This kind of message is not really common, which is why it often catches people off guard because they are not expecting it at all. This status code means that there was some sort of problem in either the syntax or semantics of a request sent by the user and this results in an invalid response from the server.

Some synonyms for this message include “bad request”, “not found”, “not acceptable” and even “unauthorized”.

25. What is the difference between HTTP and HTTPS?

Ans. There are two major differences between HTTP and HTTPS.

1. The data exchanged over HTTP is in clear text, whereas HTTPS uses cryptography to hide the data being transferred.

2. HTTP requires a server to respond with an HTTP 200 or HTTP 204 message before closing a connection, whereas HTTPS closes the connection when it sends an HTTP 200 or HTTP 204 response without waiting for the server’s response.

26. Explain persistent connections?

Ans. Persistent connections are also known as keep-alive HTTP requests. In HTTP persistent connection is used to send multiple HTTP requests over one HTTP connection and this HTTP session will be used for multiple HTTP transactions (or we can say many HTTP requests).so if you use connect() method of an HTTP client library, then that HTTP client will keep a TCP connection open for some time, so that you don’t have to do HTTP handshaking whenever an HTTP request is necessary.

persistent HTTP connections can help in performance improvement of HTTP client library as HTTP latency, problems with broken networks, etc. are going to be eliminated by using persistent HTTP connections.

27. What is an HTTP session?

Ans. An HTTP session is a sequence of request-response cycles in which all messages between a client and server follow the same initial sequence. A session may be stateful, where application data may be stored on either the client or server, or it can be stateless.

28. What is content negotiation?

Ans. Content negotiation refers to a built-in HTTP feature that enables different users to get the same resource from the web server but with a varying output format.

For example, http://www.example.com/sample.txt is an ordinary text file and http://www.example.com/sample.xml will be XML code of sample text.

29. What are cacheable methods?

Ans. Cacheable methods are those which help in database operation to be cached. These operations can include select and update statements, as well as any other operation that retrieves data from the database. The result set can also be cached by using statement caching. For example, if a method is getting called many times then we need to cache it so every time it gets called from cache instead of a database.

30. What are web sockets?

Ans. WebSocket is a new web technology that enables bi-directional communication between the browser and server. This can be used to add real-time interactivity to your web pages. The real-time part is what makes WebSockets different from HTTP streaming, comet, or long polling about which you may have already read in other articles or seen demoed at a conference somewhere. WebSockets allow the server to push messages to the browser, not just the other way around as HTTP does.

31. What is a web cache?

Ans. A web cache is an intelligent software component that stores (caches) copies of HTTP documents passing through it, so future requests for the same document can be served faster. Caching HTTP documents reduces bandwidth usage, server load, and perceived lag. Web caches are used in ISP networks, corporate intranets, and individual computer systems including personal firewalls.

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