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Advanced Topic 37 of 51 Web Development

Authentication Flows

Sessions, tokens and logins verifying users.

How it works

Authentication verifies who a user is, and authorization decides what they may do. Common flows include username and password with salted hash storage, session cookies where the server stores a session ID, token-based authentication using JWTs, OAuth 2.0 and OpenID Connect for delegated login, multi-factor authentication, magic links and passkeys based on WebAuthn. Flows cover registration, login, logout, token refresh, password reset and account recovery.

Step-by-step walkthrough

  1. The user posts a username and password.
  2. The server checks the password hash.
  3. It creates a session or token.
  4. The browser stores it in a cookie.
  5. Later requests send it so the server knows who you are.

Where it is used

Every application with accounts needs them, and identity providers such as Auth0, Okta and cloud services take over much of the work.

Common pitfall

Storing plain or weakly hashed passwords, missing rate limiting, predictable reset tokens and long-lived tokens in local storage cause breaches. Session fixation, CSRF and insecure cookies are common holes. Rolling your own cryptography is risky. Use proven libraries, bcrypt or Argon2, HTTPS everywhere, short-lived tokens and secure, HttpOnly, SameSite cookies.

Where it fits in the course

Authentication Flows is topic 37 of 51 in Web Development, rated Advanced. It follows Express and Middleware. The next topic is JWT.

Practice and explore

How to study this topic

  1. Read the explanation above and restate the definition in your own words.
  2. Open the interactive lesson and answer its mini quiz.
  3. Read the common pitfall, then write a short example that avoids it.
  4. Check your understanding in the Web Development quiz, and revisit the topic if you miss a question.

Frequently asked questions

What is Authentication Flows?
Sessions, tokens and logins verifying users. It belongs to Web Development and is an advanced-level topic.
Where do people use Authentication Flows?
Every application with accounts needs them, and identity providers such as Auth0, Okta and cloud services take over much of the work.
What is the most common mistake with Authentication Flows?
Storing plain or weakly hashed passwords, missing rate limiting, predictable reset tokens and long-lived tokens in local storage cause breaches.
What should I learn before this topic?
Start with Express and Middleware, the topic just before it in Web Development.
How can I practice it?
Answer the mini quiz in the interactive lesson, then take the Web Development quiz.
Is Authentication Flows hard to learn?
It is an Advanced topic. Expect to read the explanation more than once and to connect it with earlier topics. Working through a small example by hand helps most.
How long does it take to learn Authentication Flows?
Most learners can read the explanation and finish the interactive lesson in under an hour. Fluency comes from applying the idea, so plan a few short practice sessions with the quiz.
Which topics are related to Authentication Flows?
Express and Middleware, JWT, Node.js are closely connected. The full list is in the related topics section of this page.
What should I study after Authentication Flows?
Continue with JWT, the next topic in Web Development.

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