009 - How Browsers and Servers Talk

In my previous journal, I learned that every time I visit a website, my browser sends an HTTP Request, and the server replies with an HTTP Response.

But I started wondering something.

How does the server know what I actually want to do? Am I simply viewing a page, creating an account, updating my profile, or deleting something?

And once the server processes my request, how does it tell me whether it succeeded or failed?

That's exactly what HTTP Methods and Status Codes are for.

HTTP Methods

An HTTP Method tells the web server what action the client wants to perform.

I like thinking of it as the verb of an HTTP request. It tells the server what I'm trying to do with a resource.

Although HTTP supports many methods, these are the ones I'll probably encounter most often.

GET

The GET method asks the server to send information back.

Whenever I open a webpage, search on Google, or view a YouTube video, my browser is usually sending a GET request.

The important thing to remember is that GET only retrieves data. It doesn't modify anything on the server.

POST

The POST method is used when I want to send data to the server.

For example, when I register a new account, submit a login form, or leave a comment, my browser sends a POST request containing the information I've entered.

Unlike GET, POST usually creates something new.

PUT

The PUT method updates an existing resource.

If I edit my profile picture or change my username, my browser may send a PUT request to replace the old information with the new one.

DELETE

As the name suggests, DELETE removes a resource from the server.

For example, deleting a post, removing a comment, or permanently deleting an account may involve a DELETE request.

HTTP Status Codes

After the server receives my request, it needs to let my browser know what happened.

That's where HTTP Status Codes come in.

Every HTTP response begins with a status code that tells the browser whether the request succeeded or if something went wrong.

For example:

HTTP/1.1 200 OK

The 200 is the status code, while OK is a short description.

Instead of memorizing every code, I found it easier to understand them by their categories.

1xx — Informational

These codes tell the client that the request has been received and the communication can continue.

They're not very common in everyday browsing.

2xx — Success

These indicate that everything worked as expected.

The most common one is:

• 200 OK — The request completed successfully.

Another useful one is:

• 201 Created — A new resource was successfully created, such as a new user account or blog post.

3xx — Redirection

Sometimes a webpage has moved to another location.

Instead of showing an error, the server tells the browser where to go next.

Common examples include:

• 301 Moved Permanently — The page has permanently moved.
• 302 Found — The page has temporarily moved.

4xx — Client Errors

These errors usually mean the problem came from the client, not the server.

Some of the most common ones are:

• 400 Bad Request — The request was malformed.
• 401 Unauthorized — Authentication is required.
• 403 Forbidden — I don't have permission to access the resource.
• 404 Not Found — The requested page doesn't exist.
• 405 Method Not Allowed — I used the wrong HTTP method.

The 404 status code is probably the one I've seen the most while browsing the web.

5xx — Server Errors

Unlike 4xx errors, these usually mean something went wrong on the server itself.

Some common examples are:

• 500 Internal Server Error — The server encountered an unexpected problem.
• 503 Service Unavailable — The server is temporarily unavailable, often because it's overloaded or under maintenance.

Why This Matters

Before learning this, I thought websites simply loaded or failed to load.

Now I understand there's actually a conversation happening between my browser and the server.

The browser first tells the server what it wants to do using an HTTP Method.

The server then replies with a Status Code explaining whether that request succeeded, failed, or needs further action.

Every webpage I visit is constantly exchanging these requests and responses in the background.

Conclusion

HTTP Methods and Status Codes are two of the building blocks of web communication.

Methods describe the action I'm requesting, while Status Codes describe the result of that request.

Understanding both makes it much easier to read browser developer tools, understand APIs, and troubleshoot web applications.

Next Rabbit Hole

Now I understand what my browser is asking the server to do and how the server responds.

But HTTP requests contain much more than just a method and a status code.

They also include extra information called headers, and websites use cookies to remember who I am between requests.

That's what I'll be exploring in the next learning journal.

See you there. 👋

Reference

• TryHackMe — HTTP in Detail