What Is Hypertext Transfer Protocol (HTTP)? Mastering the Basics of HTTP

We all know how to request a webpage in a browser. You type in the URL and click the Enter button. We take it for granted, but that “request” process actually happens thanks to a highly sophisticated internet protocol called HTTP.

HTTP, or Hypertext Transfer Protocol, is the set of rules, often called the protocol, that helps servers and web browsers communicate by sending data back and forth — data like HTML pages.

Think of HTTP as the waiter at a restaurant. The waiter acts as the mediator between you (the customer) and the kitchen. Placing an order works like an HTTP request you sent through your browser.

Then the waiter takes the order, communicates it properly to the kitchen, and the waiter brings back your order, just as HTTP helps deliver the web server’s contents back to the browser.

In this article, I’ll take a closer look at HTTP and break it down in simpler terms (like comparing it to a restaurant) to help you understand everything from HTTP’s role in web communication to the versions of HTTP.

Note: I realize the accepted vernacular for a restaurant worker is “server.” But this article includes many mentions of another type of server (web servers), so I opted to use the word “waiter” for clarity.

With my restaurant analogy in mind, you have the foundation to understand the basics of HTTP. In this section, I’ll guide you through a more refined definition of HTTP, and I’ll talk about the role of HTTP in web communication.

Defining HTTP

Hypertext Transfer Protocol, as we know it today, is the foundation of data communication on the Internet. Without HTTP, your request to view a website through your browser would either not return any results or would deliver inaccurate results.

HTTP defines the formatting of all messages sent between your browser and the website server. It also decides how those messages get transmitted. Keep in mind, however, that HTTP has a set of rules.

That’s what makes it an internet protocol. HTTP, in particular, is what’s called a request-response protocol. This means the client (your browser) makes all requests, and the server sends back responses, much like how a restaurant patron always makes a request from the menu and the server helps the kitchen reply with the right food.

The Role of HTTP in Web Communication

Going back to my example of a restaurant with a waiter, I’ll show exactly how HTTP works to assist communication on the internet. Its main role is the “facilitator” that connects web browsers (clients) and servers. It does that by accepting requests from the client and sending back responses from the server.

A restaurant is no different. The restaurant patron (the client/browser) states an order (the request), which the waiter communicates back to the kitchen (the web server). The waiter then brings the correct order back to the patron, which is like the response from a web server.

What’s interesting about HTTP, however, is that it’s more akin to a waiter without a memory. We call that “statelessness,” where each request is independent. Therefore, HTTP holds no memory of previous interactions unless cookies or other session-logging technologies help.

Common HTTP Terms and Concepts

I encourage you to learn these basic terms to help you further understand how HTTP works in tandem with other concepts and tools. Once you know the lingo, it gives you a stronger grasp of how HTTP operates.

• URL (Uniform Resource Locator): The address used to access web resources. Here’s an example: http://example.com. It’s typed into the browser or clicked through a link by the user in a browser.
• HTTP Methods (Verbs): These are actions — like GET, POST, and DELETE — that trigger between web applications using HTTP.
  • GET: For fetching data like webpages or a list of products from an eCommerce store.
  • POST: Used for sending data to the server and, as a result, creating a new resource. Examples include creating a new user account or submitting a form with data.
  • PUT: This is an action for updating a current resource or making a new one if nonexistent. A prime example is updating a user’s profile.
  • DELETE: For eliminating a resource from the web server. For instance, a DELETE action might remove an entire user or blog post.
  • PATCH: This completes partial updates to a resource, like modifying a user profile without touching any other data in the profile.
• HTTP Status Codes: These are key status codes used as responses from a server. They tell the client if the response ended in a success, an error, or something else.
  • 200 OK: This informs us that not only was the request successful, but the server responded with the right data, like if a webpage loaded successfully.
  • 404 Not Found: You’ll receive this error from the server if it could not locate the resource requested. It’s most common when you type in a URL that doesn’t actually contain a webpage.
  • 500 Internal Server Error: Here’s an error that tells the client that the server ran into an unexpected issue, thus preventing it from fulfilling the request. This happens due to server-side issues.

Besides typing in the URL, the user rarely sees any of these methods or codes. HTTP takes care of actions like POST and GET on the backend. It’s the same with HTTP status codes, unless your browser displays an error code.

Beyond the basic terms and concepts of HTTP, I want you to learn the anatomy of an HTTP request and response. I’ll also further explain the client-server model along with the importance of headers in HTTP.

The Client-Server Model

The client-server model is fairly simple: the client (a browser) sends a request to get the process rolling. The HTTP protocol communicates that request to the web server, which then sends a response with the appropriate data.

Example of a typical HTTP request/response cycle:

You sit down at your computer and open a browser like Google Chrome or Mozilla Firefox.

Here’s what happens after that.

1. Request: You type a URL into the browser. As the second part of that request, the client (your browser) sends the request to the web server.
2. Response: The web server processes the request to find the necessary data. It responds using HTTP with the requested resource. For example, it might respond with an HTML page.

It’s only a two-step process, but there’s a lot that makes the HTTP request and response as efficient as possible. I’ll explain the anatomy of both requests and responses below.

Anatomy of an HTTP Request

The HTTP request requires a user, a browser, and a URL. After that, however, you’ll find several other elements working in the background to process the request.

• Request Line: Contains the HTTP method — like GET or PUT — along with the requested resource — like /index.html — and the HTTP version, like HTTP/1.1.
• Headers: Provides metadata such as user-agent, host, cookies, and content type.
• Message Body (optional): Used in methods like POST to send additional data like form data.

So, the HTTP request always has a request line and headers. Sometimes, it includes a message body. The combination of the two (or three) completes all the information needed for the server to accept the request and formulate a response.

Anatomy of an HTTP Response

After it accepts the HTTP request, the web server puts together an HTTP response. That response contains several elements:

• Status Line: Includes the HTTP version and a status code like 200 OK.
• Headers: Provide metadata about the response. For instance, the header might include the content-length and content-type.
• Message Body: Contains the actual resource, like an HTML file, JSON file, or a batch of images. Or, more likely, a combination of them all.

Without all three — the status line, header, and message body — the HTTP response is incomplete. In that case, you might see an error in your browser window.

The Importance of Headers in HTTP

I can’t stress the importance of headers in HTTP. They improve all communications between the client and server by offering useful metadata and context for the message.

Here are some common request headers and how they help:

• User-Agent: Identifies the software used by the client.
• Accept: Indicates the preferred formats for responses.
• Authorization: Keeps things secure with access control.
• Content-Type: Communicates the type of media used in the response.
• Set-Cookie: Helps store cookies on the client browser to maintain a stateful session.

All of these provide information or state some sort of rule for the client or server to abide by. A Set-Cookie, for example, tells the client to prepare for cookie storage.

As I mentioned, the status line in each HTTP response contains the HTTP version used for that communication. There are, however, several HTTP versions, all of which have their own histories and uses.

HTTP/1.0: The Beginning

In 1996, HTTP/1.0 became the first standard for web communication. It built the foundation for the most basic of request-response models for servers and clients to send data back and forth.

Key characteristics:

• One request per connection.
• Simple, but inefficient for modern web traffic because of connection overhead.
• Only allows for HEAD, GET, and POST methods.
• Very basic support for media types.

It’s also worth mentioning that HTTP/1.0 lacks the ability to keep connections alive. So, it would need some extra headers to maintain a connection.

HTTP/1.1: The Standard for Two Decades

In 1997, the world became familiar with the HTTP/1.1 version of HTTP, which experienced widespread adoption lasting for two decades. The protocol version improved performance and efficiencies in web communications.

Key improvements:

• Persistent connections: Multiple requests over a single connection, reducing overhead.
• Chunked transfer encoding: Allows dynamic content delivery.
• Host header: Enables virtual hosting (multiple domains on one IP address).
• HTTP proxy support: Allows for routing through third-party servers that more thoroughly protect an HTTP connection

There are several reasons we were all drawn to the HTTP/1.1 version for so long. It reduced latency and network congestion. It negotiated with ease, and it offered perhaps the first glance at useful caching mechanisms in the world of HTTP.

HTTP/2: Speeding Up the Web

The year 2015 brought about the HTTP version called HTTP/2. With it came major improvements in performance and latency. The whole point of the new protocol version was to address the limitations of HTTP/1.1 and to make web applications faster in general.

Key features:

• Multiplexing: Allows multiple requests and responses over one connection.
• Header compression: Reduces the size of HTTP headers, speeding up data transfer.
• Server push: Servers can preemptively send resources to the client before requested, improving page load times.
• Request prioritization: Puts some requests in front of others depending on the client’s needs.

I appreciate so many things about HTTP/2, much of which revolves around its focus on fixing HTTP/1.1 inefficiencies. For instance, HTTP/2 minimizes issues with redundant headers and head-of-line blocking.

HTTP/3: The Next Generation

The newest generation of HTTP, called HTTP/3, blasted onto the scene in 2020. It uses QUIC (a UDP-based protocol) instead of the previously used TCP. This results in further improvements for latency, performance, and reliability.

Key features:

• Reduced Latency: Faster connections thanks to QUIC.
• Improved Performance in High-Latency Networks: More resilient to packet loss, making it ideal for mobile and unstable networks.
• Security by Default: TLS encryption that’s built into HTTP/3.

The HTTP/3 protocol is backward compatible with its previous version for smooth infrastructural transitions. In my opinion, QUIC has the potential to completely replace TCP, and it’s all thanks to its ability to create speedier and more secure web connections.

You’ve seen it in your browser’s address bar. It’s that https:// part that’s just slightly different than the usual http://. What does it mean? Has your browsing experience changed at all? The answer is yes, but not in a way you might notice. The change mainly makes you significantly more secure online.

What Is HTTPS?

HTTPS, or Hypertext Transfer Protocol Secure, refers to a more secure version of HTTP that’s layered with SSL/TLS encryption. That layer secures all data transferred on a website.

When I’m browsing as a user, HTTPS protects any data I send through a website, like when typing in my credit card information. It’s also essential for making businesses — the ones that own websites — more secure.

HTTPS boosts data privacy all around and it strengthens the integrity between clients and servers.

How HTTPS Works

I find it useful to think about HTTPS as a more exclusive dining setting, as opposed to my hypothetical “waiter in the restaurant” analogy that refers to basic HTTP. HTTPS is more like a country club.

Country clubs have security at the front. You’re asked to prove your identity with a member card. Even smaller transactions inside the club restaurant require you to put the bill on your member account. Otherwise, you’re not let into the restaurant, and you can’t make an order.

HTTPS is similar. Between the client and server, it asks for an SSL/TLS handshake where encryption keys get exchanged to generate a secure connection.

Much like multiple levels of security at a country club, HTTPS uses two combined encryption methods:

• Symmetric encryption: Best for fast encryption of large data sets. It uses one key to encrypt and decrypt all data between the client and server.
• Asymmetric encryption: This option uses two keys. One key is public and used for encryption, while another, the private key, decrypts communications between clients and servers. It’s slower but more secure.

On top of all that, HTTPS takes advantage of certificates. Often called SSL or SSL/TLS certificates, these digital documents verify website identities for an added layer of security. You can get them from trusted certificate authorities like DigiCert and Let’s Encrypt.

Why HTTPS Is Essential

HTTPS is a more secure protocol and often required by municipalities to even operate a website. Beyond that, you’ll find many other benefits to HTTPS:

• Data protection: Ensures sensitive information like payment information and login details remains encrypted.
• SEO Benefits: Google uses HTTPS as a ranking factor, favoring secure websites in search results.
• Building trust: HTTPS reassures users that their data is safe, leading to higher user confidence and engagement.

I’ll also add that data encryption and authentication from HTTPS build data integrity for your business. It gives you confidence in knowing that no one intercepted a communication and altered any data.

Earlier I spoke about HTTP methods for data transfer. There were methods like GET, POST, PUT, and DELETE. I outlined the absolute basics, but now I’d like to dive into their specific use cases.

GET Method: Retrieving Data

The GET method, the one we all complete regularly, requests data from a web server. But it’s more specific than that. A GET action specifies a resource the user wants, most likely a URL to bring up a webpage.

Characteristics:

• No message body in the request.
• Typically used for fetching resources.
• Cacheable for faster performance in the future.

From your perspective, all you need to know is that the GET request is the URL you type into the browser’s address bar. Therefore, it’s technically visible to others. That’s why GET actions rarely transmit sensitive data. Instead, we use them to fetch data for APIs or load websites.

POST Method: Submitting Data

The POST method works as an HTTP request for sending data to a server. That may involve submitting something like form data, where the data is updated in a database.

Characteristics:

• Data gets sent in the message body, so it can send larger amounts of data.
• Used for actions like registration or uploading files.
• Protects sensitive information thanks to its transmission via request body.

Think about any time a website might need to change data. That’s usually when the POST method goes into action. I’m talking about registering users, uploading files, or submitting forms.

PUT Method: Updating Resources

The PUT method works differently than POST in that it updates or completely replaces a resource. This HTTP request method helps with updating user profiles and modifying resources in RESTful API scenarios.

Characteristics:

• Contains the updated resource in the message body.
• Typically used for updating files or database records.
• It’s usually impossible to cache a PUT request.

To get more specific, a PUT action works best when a complete update of a server’s resources is required. So, it wouldn’t happen for a slight modification of a user profile but an overhaul or replacement.

DELETE Method: Removing Resources

The DELETE method deletes a resource from a web server. I see it mostly activated with RESTful APIs. After all, it’s common for a RESTful API to delete items like database entries.

Characteristics:

• Instructs the server to remove a resource.
• Never ends up in a cache.
• Uses what’s called a URI (Uniform Resource Identifier) to request the deletion of a resource — instead of using a URL or request body.

I’ve found the DELETE method most prominent when the client requests the server to delete something like a user account or a resource from a database.

Other Methods: PATCH, HEAD, OPTIONS

Here are some other HTTP request methods I consider worthwhile to discuss:

• PATCH: Updates a resource partially (instead of replacing it like PUT).
• HEAD: Similar to GET, but only retrieves headers (without the message body).
• OPTIONS: Used to describe communication options for a specific resource.

All three methods increase the efficiency of communications between servers and clients. They give the client granular control over messaging, making them quite complementary to the main HTTP request methods.

After the client makes a request, the server may reply with a status code.

Sometimes a code means there’s nothing to worry about. Other times you may need to look into issues with your internet connection, a website’s server, or even your browser. But most of the time, you, as the user, won’t see anything at all.

Here are the most common HTTP status codes and what they mean:

• Informational (1xx)
  • Example: 100 Continue — The request has been received and the process can continue.
• Success (2xx)
  • Example: 200 OK — The request was successful, and the server returned the requested resource.
• Redirection (3xx)
  • Example: 301 Moved Permanently — The requested resource has been permanently moved to a new location.
  • Example: 302 Found — The requested resource has been temporarily moved.
• Client Errors (4xx)
  • Example: 404 Not Found — The server could not find the requested resource.
  • Example: 403 Forbidden — The client is not authorized to access the resource.
• Server Errors (5xx)
  • Example: 500 Internal Server Error — The server encountered an unexpected condition.
  • Example: 502 Bad Gateway — The server received an invalid response from the upstream server.

I noted before that the users don’t actually see most codes unless there’s an error. So what’s the point of them? Well, status codes assist clients.

Those clients can then see the results of their requests and take action based on those results. For instance, a browser may retry the request or redirect to somewhere else.

The caching of HTTP occurs in specific areas. I’ve explained how some HTTP request methods don’t land in any caches. However, there are plenty of elements within the HTTP system that use caching.

What Is Caching?

Caching refers to the storing of files — in this case, items like CSS, HTML, and images — for their quick retrieval by a browser without reloading them from the server.

In short, caching saves things locally so the server doesn’t have to do the work again.

How HTTP Caching Works

HTTP caching is a unique form of caching that happens on the browser side or server side. The idea is for either of those to create a cache that stores resources. As a result, the server doesn’t have to work as much.

Here are some key headers used in HTTP caching:

• ETag: Gives each resource a unique identifier for validation.
• Expires: Provides an expiration date for every piece of cached data.
• Cache-Control: Dictates all caching policies. For instance, it sets ‌max-age to ensure the freshness of resources.

When I talk about browser caching, I mean that your browser saves local data without being touched by the server. For server-side caching, however, mechanisms like Nginx caching log responses, allowing the server to help itself with processing load.

Benefits of HTTP Caching

Here’s why you should care about HTTP caching:

1. It allows for faster page load times for the user.
2. The server sees lower bandwidth consumption and reduced server load.
3. The user experience improves.

Everyone wins, in my opinion: the web host, the user, the website owner, even search engines like to see faster page loads and improved user experiences.

Whenever I discuss HTTP, I always come to the conclusion that the protocol is a constantly growing set of rules. That means challenges exist. And you must be prepared for those challenges.

The Impact of HTTP on Web Performance

My view of HTTP ties directly to how it affects web performance. I enjoy faster website speeds, scalability, and user experience. Luckily for me, HTTP improves all of those.

That’s particularly true with the evolution of HTTP from HTTP/1.1 to HTTP/2 to HTTP/3. The protocol regularly becomes more advanced, and that means we can expect enhanced speeds and scalability well into the future.

Security Challenges in HTTP

HTTP by itself makes me think of an armored truck without its two guards and other security protocols. Sure, the truck is fast enough and probably pretty secure to transfer money to its destination, but it’s missing several components to make it ironclad.

One of the biggest downsides to HTTP is its lack of encryption. This is why you should only browse sites that use HTTPS. Look for the padlock icon in the address bar to confirm a site is secure.

Likewise, HTTP is vulnerable to man-in-the-middle attacks and data breaches. HTTPS, however, encrypts the plain text sent by HTTP. And you get security guards in the form of SSL/TLS.

Innovations and the Future of HTTP

I’m excited to see advancements like HTTP/3 and QUIC. They promise reductions in latency and boosted reliability for connections. Some trends I also encourage you to read more about include the creation of protocols designed for more efficiency and security on the internet. What’s going to replace HTTP/3?

HTTP is a messenger. A mediator. A security enforcer (at least in its HTTPS form). HTTP makes sure you see the websites you want to see when browsing. You get all that with speed, efficiency, and security.

And, as I’ve explained with many use cases, HTTP helps more advanced operations for APIs, databases, and even cloud computing. It’s everywhere you look on the internet, so I’m glad you took the time to learn about HTTP!