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 every API request, covering API keys, OAuth 2.0 flows, JWT tokens, scopes and permissions, and security best practices to keep credentials safe.

What You'll Learn

How to document different authentication methods, how to explain OAuth 2.0 flows clearly, how to document API key acquisition and usage, how to describe scopes and permissions, how to show authentication errors, and how to write security best practices.

Why It Matters

Authentication is the first thing developers implement when integrating an API. Missing or unclear authentication documentation is the number one cause of support tickets. Clear auth docs reduce first-request friction and keep credentials secure.

Real-World Use

The DodaTech API supports both API key authentication for server-to-server integration and OAuth 2.0 for third-party applications. Doda Browser and DodaZIP use OAuth to let users grant permissions without sharing their master API key.

Authentication Methods

flowchart TD
  A[Authentication Methods] --> B[API Keys]
  A --> C[OAuth 2.0]
  A --> D[JWT Bearer Tokens]
  B --> E[Header-based]
  B --> F[Query parameter]
  C --> G[Authorization Code]
  C --> H[Client Credentials]
  C --> I[PKCE]
  A:::current
  classDef current fill:#f90,color:#fff,stroke:#333,stroke-width:2px

API Key Authentication

API keys are the simplest authentication method. Document how to get a key and how to use it.

## API Key Authentication

All API requests require an API key. Pass it in the `Authorization` header:

Authorization: Bearer YOUR_API_KEY

### Getting an API Key

1. Log in to the [DodaTech Dashboard](https://dashboard.dodatech.com)
2. Go to **Settings > API Keys**
3. Click **Generate New Key**
4. Give it a name and select the scopes
5. Copy the key immediately. You will not see it again.

### Using the API Key

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

import os
from dodatech import Client

client = Client(api_key=os.environ["DODATECH_API_KEY"])
files = client.files.list()

## OAuth 2.0 Documentation

OAuth 2.0 is more complex. Document each flow separately with clear steps.

```markdown
## OAuth 2.0 Authorization Code Flow

Use this flow when your application needs to access DodaTech APIs on
behalf of a user (e.g., a third-party app using DodaZIP's compression).

### Step 1: Get Authorization

Redirect the user to:

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 2: Handle the Callback

The user is redirected back to your redirect URI with an authorization code:

https://yourapp.com/callback?code=auth_code_abc123&state=random-state-string

Verify that the `state` parameter matches the one you sent. This prevents
CSRF attacks.

### Step 3: Exchange Code for Token

```bash
curl -X POST https://auth.dodatech.com/token \
  -H "Content-Type: application/x-www-form-urlencoded" \
  -d "grant_type=authorization_code" \
  -d "code=auth_code_abc123" \
  -d "redirect_uri=https://yourapp.com/callback" \
  -d "client_id=YOUR_CLIENT_ID" \
  -d "client_secret=YOUR_CLIENT_SECRET"

Step 4: Use the Access Token

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

## Scopes and Permissions

Document every scope, what it grants access to, and whether it requires approval.

```markdown
## Scopes

| Scope | Access | Requires Approval |
|-------|--------|-------------------|
| `files:read` | View files and metadata | No |
| `files:write` | Upload, compress, delete files | No |
| `jobs:read` | View job status | No |
| `jobs:write` | Create and cancel jobs | No |
| `webhooks:read` | View webhook configurations | Yes |
| `webhooks:write` | Create and modify webhooks | Yes |
| `admin` | Full account access | Yes |

Authentication Errors

Document the most common authentication errors and how to fix them.

// 401 Unauthorized — Missing or invalid API key
{
  "error": {
    "code": "UNAUTHORIZED",
    "message": "Invalid or missing API key.",
    "docs_url": "https://docs.dodatech.com/api/auth"
  }
}

// 403 Forbidden — Insufficient permissions
{
  "error": {
    "code": "FORBIDDEN",
    "message": "API key lacks required scope: files:write.",
    "required_scope": "files:write",
    "docs_url": "https://docs.dodatech.com/api/scopes"
  }
}

Security Best Practices

## Security Best Practices

1. **Store API keys in environment variables**, never in source code.
   Durga Antivirus Pro scans repositories for committed credentials.

2. **Rotate keys regularly** — Generate new keys every 90 days and
   revoke old ones.

3. **Use the minimum required scope** — Do not use admin scope for
   read-only operations.

4. **Implement key revocation** — If you suspect a key is compromised,
   revoke it immediately from the dashboard.

5. **Use OAuth for third-party apps** — Never share your master API key
   with third-party applications. Use OAuth 2.0 instead.

Common Mistakes

1. No Authentication Examples

Documenting authentication method without a complete HTTP request example forces developers to guess the header format.

2. Confusing OAuth Flows

Explaining OAuth without distinguishing authorization code from client credentials flow causes implementation errors. Document each flow separately.

3. Not Documenting Token Expiry

Omitting information about how long tokens last and how to refresh them causes mysterious 401 errors in production.

4. Missing Scope Documentation

Not listing available scopes and their permissions causes over-privileged API keys and security risks.

5. No Error Code Reference

Showing only successful authentication without error responses leaves developers unprepared for common issues.

6. Storing Keys in Code Examples

Hardcoding keys in documentation examples teaches bad security habits. Always use placeholders and environment variables.

7. No Revocation Instructions

Not documenting how to revoke compromised credentials leaves security incidents unresolved until support is contacted.

Practice Questions

1. What are the three most common API authentication methods?

API keys (simple header-based), OAuth 2.0 (delegated authorization with multiple flows), and JWT Bearer tokens (self-contained tokens with claims).

2. Why should API documentation never show real API keys?

Hardcoded keys in documentation normalize bad security habits. Always use placeholder values like YOUR_API_KEY and instruct users to store keys in environment variables.

3. What is the purpose of OAuth 2.0 scopes?

Scopes limit what an access token can do. A files:read scope allows viewing files but not deleting them. Scopes implement the principle of Least Privilege.

4. Why include a state parameter in OAuth authorization requests?

The state parameter prevents CSRF Attacks. The server returns the same state value in the callback, allowing you to verify the response matches your request.

5. Challenge: Write complete authentication documentation for a fictional API that supports both API key authentication and OAuth 2.0 authorization code flow. Include security best practices and error responses.

FAQ

Mini Project: Write Auth Documentation

Write complete authentication documentation for an API of your choice. Cover at least two authentication methods, include complete code examples for each method, document scopes with a table, show authentication error responses, and include security best practices specific to your API.

What's Next

Authentication keeps bad actors out. Now learn how to write Error Documentation that helps developers fix problems quickly. Then explore Rate Limiting Documentation for designing fair usage policies.