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Understand oauth2 blog

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+---
+layout: post
+title: "Understanding OAuth2: The backbone of modern authorization"
+description: A quick guide to OAuth2, its flows, and when to use each one.
+date: 2025-06-12
+cover: /images/blog/understand-oauth2/cover.png
+timeToRead: 06
+author: laura-du-ry
+callToAction: true
+unlisted: true
+category: product
+---
+
+In today’s interconnected app ecosystem, users expect seamless, secure access across services. OAuth2 has emerged as the industry standard for handling secure delegated access, making it a critical protocol for developers to understand.
+
+This guide explains OAuth2, how it works, the different flows available, and when to use each one, helping you build secure, scalable authorization experiences.
+
+# What is OAuth2?
+
+OAuth2 is an open standard for authorization. It allows users to grant limited access to their resources on one service to another service without sharing credentials.
+
+Rather than handing out a username and password, users authorize apps to act on their behalf using access tokens. OAuth2 ensures that:
+
+- Apps never directly handle user credentials.
+- Users retain control over what permissions they grant.
+- Access can be easily revoked.
+
+# Core components of OAuth2
+
+Before diving into the flows, it's important to understand the key players:
+
+- **Resource owner**: The user who authorizes access to their data.
+- **Client**: The application requesting access.
+- **Authorization server**: Issues access tokens after authenticating the user.
+- **Resource server**: Hosts the protected resources.
+
+These components work together to ensure secure authorization across systems.
+
+Refer to the OAuth2 [documentation](/docs/product/auth/oauth2) for complete technical details.
+
+# How OAuth2 works: A simple flow
+
+1. **Authorization request**: The client asks the resource owner for permission.
+2. **Authorization grant**: If the user consents, the server issues a grant (authorization code, token, etc.).
+3. **Token request**: The client exchanges the grant for an access token.
+4. **Resource access**: The client uses the token to access protected resources.
+
+Tokens are typically short-lived and scoped, meaning they only allow the operations the user approved.
+
+# Major OAuth2 flows
+
+OAuth2 offers different "flows" to accommodate various scenarios. Here's a breakdown of the major ones:
+
+## 1. Authorization code flow
+
+**Best for**: Server-side applications
+
+- User authenticates via browser.
+- Client receives an authorization code.
+- Server exchanges the code for an access token.
+
+**Advantages**:
+
+- Highly secure (authorization code exchanged server-side).
+- Supports refresh tokens.
+
+**Typical use cases**:
+
+- Web apps with secure backend servers.
+
+{% call_to_action title="Customer identity without the hassle" description="Add secure authentication for your users in just a couple of minutes." point1="Multiple OAuth providers" point2="Built-in security" point3="Custom roles and permissions" point4="Integrates with your favourite SDK" cta="Contact sales" url="https://appwrite.io/contact-us/enterprise" /%}
+
+
+## 2. Authorization code flow with PKCE (Proof Key for Code Exchange)
+
+**Best for**: Mobile and SPA (Single Page Applications)
+
+- Similar to Authorization Code Flow, but with an added security layer (PKCE).
+- Prevents interception attacks.
+
+**Advantages**:
+
+- Stronger protection for public clients.
+
+**Typical use cases**:
+
+- Mobile apps, SPAs.
+
+## 3. Client credentials flow
+
+**Best for**: Machine-to-machine (M2M) communication
+
+- No user interaction.
+- Client authenticates itself to obtain an access token.
+
+**Advantages**:
+
+- Efficient for service-to-service communication.
+
+**Typical use cases**:
+
+- APIs accessed by backend services.
+
+## 4. Implicit Flow (Legacy)
+
+**Best for**: SPAs (historically)
+
+- Tokens returned directly in browser URL.
+- Faster but less secure.
+
+**Note**: Now largely replaced by Authorization Code Flow with PKCE due to security risks.
+
+## 5. Device authorization flow
+
+**Best for**: Devices without browsers/keyboards
+
+- User authenticates on a separate device.
+- Device polls authorization server for approval.
+
+**Typical use cases**:
+
+- Smart TVs, IoT devices.
+
+[Appwrite Auth](/products/auth) supports all major OAuth2 flows, making it easy to integrate secure authentication into any app
+
+# OAuth2 Tokens: Access and refresh
+
+OAuth2 commonly uses two types of tokens:
+
+- **Access Token**: Grants access to protected resources.
+- **Refresh Token**: Used to obtain new access tokens without re-authenticating the user.
+
+Tokens are often JWTs (JSON Web Tokens) containing claims about the user and the permissions granted.
+
+# When to Use OAuth2
+
+- **Third-party integrations**: Allowing users to connect external services securely.
+- **APIs**: Protecting APIs from unauthorized access.
+- **Mobile and web Apps**: Enabling secure login and data access without managing credentials.
+- **B2B applications**: Secure service-to-service communication.
+
+# Common OAuth2 pitfalls
+
+- **Over-scoped tokens**: Granting too many permissions.
+- **Insecure storage**: Storing tokens in insecure locations (e.g., localStorage without encryption).
+- **Ignoring token expiration**: Failing to handle token refresh flows.
+- **Misusing Implicit Flow**: Using legacy flows where better options (PKCE) are available.
+
+# OAuth2: A key enabler of modern security
+
+OAuth2 powers secure, flexible authorization across the modern internet. Understanding its core flows and best practices helps developers build safer, more user-friendly apps.
+
+Choosing the proper OAuth2 flow based on your application's architecture and user needs is critical to balancing security, usability, and scalability.
+
+Ready to explore OAuth2 more deeply? Check
+
+- [Appwrite Authentication docs](/docs/products/auth)
+- [Overview of all the OAuth providers](/integrations#auth)
+- [Appwrite Authentication overview](/products/auth)