What Happens When You Click “Login”? Understanding Authentication for Beginners
You enter your email and password on a website, click Login , and suddenly you're inside your account. It feels like a simple action. But what actually happens after you click that button? How does the website know that the email and password belong to you? Where does the password go? How does the server remember that you've logged in? And how does it know what you're allowed to access? Let's…
When you enter your email and password on a website and click the "Login" button, several processes occur in the background to verify your credentials and grant you access. Here's a detailed breakdown of what happens:
1. You enter your credentials on a login form, which consists of an email and password field. Upon clicking "Login," this information is sent from your browser to the website's backend server.
2. The browser sends an HTTP POST request to the backend API endpoint responsible for handling login requests, typically formatted as JSON. The request body contains the email and password entered by the user.
3. API endpoints are specific URLs that allow communication between the client (browser) and the server (backend). In this case, the POST /api/login endpoint receives the login request and forwards it to the backend for processing.
4. Upon receiving the request, the backend server validates the input. It checks if the necessary fields (email and password) are present and in the correct format. This validation step is crucial to ensure that the data received is trustworthy and complete.
5. After validation, the backend server queries the database to check if a user account exists with the provided email address. The server does not store passwords in plain text due to security reasons. Instead, it stores a hashed version of the password. During login, the server hashes the provided password using a secure hashing algorithm (e.g., bcrypt) and compares it to the stored hash.
6. If the hashed passwords match, the backend authenticates the user. The user is then granted access based on their role and permissions within the system. This process is called authentication, which verifies the user's identity.
7. After successful authentication, the backend generates an authentication token (e.g., JWT) and sends it back to the browser. This token is usually stored in the browser's local storage or cookies and included in subsequent requests to prove the user's authenticated status.
8. The browser, upon receiving the authentication token, sends it along with subsequent requests to authorize the user's access to protected resources. The backend verifies the token's validity and grants or denies access accordingly.
In summary, when you click "Login," your credentials are sent to the backend server, which validates them, checks for the user's existence in the database, verifies the password using a secure hashing algorithm, and grants access if the credentials are correct. Authentication ensures that the user is who they claim to be, while authorization determines what resources the authenticated user can access.
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
