Authentication Documentation — Complete Guide

In this tutorial, you will learn about Authentication Documentation. We cover key concepts, practical examples, and best practices to help you master this topic.

Authentication documentation shows developers how to obtain credentials and authenticate API requests by covering API key acquisition, OAuth 2.0 authorization flows, supported scopes and permissions, authentication error responses, and security best practices for credential management.

What You'll Learn

How to document API key authentication, how to explain OAuth 2.0 flows in simple terms, how to document scopes and permissions, how to show authentication error responses with troubleshooting steps, and how to write security best practices for credential management.

Why It Matters

Authentication is the first thing developers implement when integrating an API. It is also the most common source of support tickets. Clear authentication documentation that shows exactly how to get and use credentials is essential for a smooth developer experience.

Real-World Use

The DodaTech API supports both API key authentication for server-to-server integrations and OAuth 2.0 for third-party apps. The documentation shows both methods with step-by-step instructions, code examples, and troubleshooting for common errors.

Authentication Flow

flowchart TD
  A[Developer] --> B{Authentication Method?}
  B --> C[API Key]
  B --> D[OAuth 2.0]
  C --> E[Get key from dashboard]
  C --> F[Include in Authorization header]
  D --> G[Register application]
  D --> H[Choose OAuth flow]
  D --> I[Get access token]
  E --> J[Making Authenticated Requests]
  F --> J
  I --> J
  A:::current
  classDef current fill:#f90,color:#fff,stroke:#333,stroke-width:2px

API Key Authentication

API keys are the simplest authentication method. Document every step.

## API Key Authentication

### Getting an API Key

1. Log in to the [DodaTech Dashboard](https://dashboard.dodatech.com)
2. Navigate to **Settings > API Keys**
3. Click **Generate New Key**
4. Enter a descriptive name (e.g., "Production Server")
5. Select the required scopes
6. Click **Generate** and copy the key immediately

> Store your API key in an environment variable. Never hardcode it or
> commit it to version control. Durga Antivirus Pro scans repositories
> for accidentally committed credentials.

### Using Your API Key

Include the key in every request using the `Authorization` header:

Authorization: Bearer YOUR_API_KEY

```bash
curl -H "Authorization: Bearer YOUR_API_KEY" \
  https://api.dodatech.com/v2/files

## OAuth 2.0 Documentation

OAuth 2.0 has multiple flows. Document each flow separately.

```markdown
## OAuth 2.0 Authorization Code Flow

Use this flow when your application needs to access the API on behalf
of a user, such as a third-party integration with DodaZIP.

### Step 1: Register Your Application

Register your application in the [Developer Portal](https://developers.dodatech.com)
to get a `client_id` and `client_secret`.

### Step 2: Redirect User to Authorization URL

https://auth.dodatech.com/authorize? response_type=code& client_id=YOUR_CLIENT_ID& redirect_uri=https://yourapp.com/callback& scope=files:read+files:write& state=random-state-string

### Step 3: Handle the Callback

```python
from flask import request, redirect
import requests

@app.route("/callback")
def oauth_callback():
    code = request.args.get("code")
    state = request.args.get("state")

    # Verify state matches your original request
    if state != session["oauth_state"]:
        return "Invalid state parameter", 400

    # Exchange code for token
    response = requests.post("https://auth.dodatech.com/token", data={
        "grant_type": "authorization_code",
        "code": code,
        "redirect_uri": "https://yourapp.com/callback",
        "client_id": "YOUR_CLIENT_ID",
        "client_secret": "YOUR_CLIENT_SECRET",
    })

    token_data = response.json()
    access_token = token_data["access_token"]
    return f"Authenticated! Token: {access_token[:20]}..."

## Scope Documentation

Document every scope with its permissions.

```markdown
## Scopes and Permissions

| Scope | Access Level | Description |
|-------|-------------|-------------|
| `files:read` | Read | View files and their metadata |
| `files:write` | Read + Write | Upload, compress, and delete files |
| `jobs:read` | Read | View compression job status |
| `jobs:write` | Read + Write | Create and cancel compression jobs |
| `admin` | Full | All operations including billing and team management |

> Assign the minimum required scopes. A read-only integration should
> only request `files:read`, not `admin`.

## Authentication Error Documentation

Document common authentication errors and how to fix them.

```json
// 401 Missing API Key
{
  "code": "MISSING_API_KEY",
  "message": "No API key provided.",
  "detail": "The Authorization header is missing from the request.",
  "solution": "Add 'Authorization: Bearer YOUR_API_KEY' to your request headers."
}

// 401 Invalid API Key
{
  "code": "INVALID_API_KEY",
  "message": "API key is not valid.",
  "detail": "The provided key does not match any active key in our system.",
  "solution": "Generate a new API key from the dashboard and update your application."
}

// 403 Insufficient Scope
{
  "code": "INSUFFICIENT_SCOPE",
  "message": "API key lacks required permission.",
  "detail": "This endpoint requires the 'files:write' scope.",
  "solution": "Generate a new API key with the 'files:write' scope."
}

## Common Mistakes

### 1. No Authentication Documentation

Not documenting how to get and use credentials. This is the most common documentation gap and the number one cause of support tickets.

### 2. Confusing OAuth Flows

Explaining OAuth without distinguishing authorization code from client credentials flow. Document each flow separately with its use case.

### 3. Missing Token Expiry Information

Omitting how long tokens last and how to refresh them. Developers get mysterious 401 errors when tokens expire.

### 4. No Scope Documentation

Not listing available scopes and what each one grants access to. Developers over-provision permissions to be safe.

### 5. Hardcoded Credentials in Examples

Showing real or example API keys in documentation teaches bad habits. Always use placeholders and environment variables.

### 6. No Error Examples

Showing only successful authentication flow without error responses. Developers need to know what happens when credentials are wrong.

### 7. Missing Revocation Instructions

Not documenting how to revoke compromised credentials. Developers cannot respond to security incidents without clear instructions.

## Practice Questions

**1. What are the two most common API authentication methods?**

API keys (simple, header-based) and OAuth 2.0 (delegated authorization with multiple flows for different use cases).

**2. Why should API keys be stored in environment variables?**

Environment variables keep credentials out of source code, preventing accidental commits to version control. Hardcoded keys are a common security vulnerability.

**3. What is the purpose of the state parameter in OAuth 2.0?**

The state parameter prevents <a href="/web-security/csrf-attacks/">CSRF Attacks</a>. The server returns the same state value in the callback, allowing the developer to verify the response matches their original request.

**4. What is the principle of Least Privilege for API scopes?**

Only request the minimum scopes needed for your integration. A read-only integration should request files:read, not admin. This limits the impact of a compromised credential.

**5. Challenge:** Write complete authentication documentation for an API that supports both API key authentication and the OAuth 2.0 authorization code flow. Include scopes table, error responses, and security best practices.

## FAQ

<details style="margin-bottom:12px;border:1px solid #e2e8f0;border-radius:10px;overflow:hidden"><summary style="cursor:pointer;padding:14px 18px;font-weight:600;font-size:1.05rem;background:#f8fafc;border-bottom:1px solid #e2e8f0;color:#1e293b">What is the difference between authentication and authorization?</summary><div style="padding:14px 18px;color:#475569;line-height:1.7;background:#fff"><p>Authentication verifies who you are (API key or OAuth token). Authorization determines what you can do (scopes and permissions). Both are essential and should be documented separately.</p>
</div></details>

<details style="margin-bottom:12px;border:1px solid #e2e8f0;border-radius:10px;overflow:hidden"><summary style="cursor:pointer;padding:14px 18px;font-weight:600;font-size:1.05rem;background:#f8fafc;border-bottom:1px solid #e2e8f0;color:#1e293b">Should I support both API keys and OAuth 2.0?</summary><div style="padding:14px 18px;color:#475569;line-height:1.7;background:#fff"><p>Yes. API keys are simpler for server-to-server integrations. OAuth 2.0 is necessary for third-party apps acting on behalf of users. Supporting both covers all integration patterns.</p>
</div></details>

<details style="margin-bottom:12px;border:1px solid #e2e8f0;border-radius:10px;overflow:hidden"><summary style="cursor:pointer;padding:14px 18px;font-weight:600;font-size:1.05rem;background:#f8fafc;border-bottom:1px solid #e2e8f0;color:#1e293b">How do I document API key rotation?</summary><div style="padding:14px 18px;color:#475569;line-height:1.7;background:#fff"><p>Show the steps to generate a new key, update the application with the new key, verify the new key works, and revoke the old key. Recommend 90-day rotation cycles.</p>
</div></details>

<details style="margin-bottom:12px;border:1px solid #e2e8f0;border-radius:10px;overflow:hidden"><summary style="cursor:pointer;padding:14px 18px;font-weight:600;font-size:1.05rem;background:#f8fafc;border-bottom:1px solid #e2e8f0;color:#1e293b">What format should the Authorization header use?</summary><div style="padding:14px 18px;color:#475569;line-height:1.7;background:#fff"><p>The standard format is: Authorization: Bearer YOUR_TOKEN. Some APIs use Authorization: Token YOUR_KEY or custom formats. Document your exact format with a working example.</p>
</div></details>

<details style="margin-bottom:12px;border:1px solid #e2e8f0;border-radius:10px;overflow:hidden"><summary style="cursor:pointer;padding:14px 18px;font-weight:600;font-size:1.05rem;background:#f8fafc;border-bottom:1px solid #e2e8f0;color:#1e293b">How do I handle authentication across multiple environments?</summary><div style="padding:14px 18px;color:#475569;line-height:1.7;background:#fff"><p>Document environment-specific setup for development, staging, and production. Recommend different API keys for each environment to prevent accidental production access.</p>
</div></details>

## Mini Project: Write Auth Documentation

Create complete authentication documentation for an API. Include API key authentication with dashboard instructions and code examples, OAuth 2.0 authorization code flow with callback example, a scopes and permissions table, authentication error responses with troubleshooting, and security best practices.

## What's Next

Authentication secures access. Now learn to document usage limits with Rate Limit Documentation. Then explore Code Examples Best Practices.