Bearer token authentication in Rest API - Step-by-Step Execution

Concept Flow - Bearer token authentication

Client sends request

↓

Check Authorization header

↓

Extract Bearer token

↓

Validate token

↓

Allow access

↓

Send response

The client sends a request with a Bearer token in the Authorization header. The server extracts and validates the token, then allows or denies access accordingly.

Execution Sample

Rest API

GET /api/data HTTP/1.1
Authorization: Bearer abc123token

// Server extracts 'abc123token'
// Server validates token
// Server responds with data if valid

This example shows a client sending a GET request with a Bearer token, which the server checks before responding.

Execution Table

Step	Action	Input/Condition	Result/Output
1	Receive HTTP request	Authorization header present	Header read: 'Bearer abc123token'
2	Extract token	Header value 'Bearer abc123token'	Token extracted: 'abc123token'
3	Validate token	Token 'abc123token'	Token is valid
4	Authorize request	Token valid	Access granted
5	Send response	Access granted	200 OK with requested data
6	End	Request processed	Execution stops

💡 Request processing ends after sending response based on token validation

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
Authorization header	None	'Bearer abc123token'	'Bearer abc123token'	'Bearer abc123token'
Token	None	'abc123token'	'abc123token'	'abc123token'
Token valid?	Unknown	Unknown	True	True
Access granted?	False	False	True	True

Key Moments - 2 Insights

Why do we extract the token from the Authorization header?

Because the token is sent as part of the Authorization header with the prefix 'Bearer '. We must remove 'Bearer ' to get the actual token string, as shown in step 2 of the execution_table.

What happens if the token is invalid?

If the token is invalid, the server denies access and sends an error response instead of the requested data. This is the alternative path after step 3 in the concept_flow.

Visual Quiz - 3 Questions

Look at the execution_table, what is the token value after step 2?

A 'abc123token'

B None

C 'Bearer abc123token'

D 'token abc123'

💡 Hint

Check the 'Token' variable value in variable_tracker after step 2

At which step does the server decide to grant access?

A Step 1

B Step 3

C Step 4

D Step 5

💡 Hint

Look at the 'Authorize request' action in execution_table

If the Authorization header was missing, what would happen?

A Token would be empty but access granted

B Token extraction would fail and access would be denied

C Server would ignore authentication and allow access

D Server would crash

💡 Hint

Refer to concept_flow where Authorization header is checked first

Concept Snapshot

Bearer token authentication uses the Authorization header with 'Bearer <token>'.
The server extracts the token, validates it, and grants or denies access.
If token is valid, server responds with requested data.
If invalid or missing, server denies access with error.
This method secures API endpoints simply and effectively.

Full Transcript

Bearer token authentication works by the client sending a token in the Authorization header of an HTTP request. The header looks like 'Authorization: Bearer abc123token'. The server reads this header, extracts the token by removing the 'Bearer ' prefix, and then checks if the token is valid. If the token is valid, the server allows access to the requested resource and sends back the data with a 200 OK response. If the token is invalid or missing, the server denies access and sends an error response. This process ensures only authorized clients can access protected API endpoints.