API authentication with Sanctum in Laravel - Step-by-Step Execution

Concept Flow - API authentication with Sanctum

Client sends login request

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Sanctum verifies credentials

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Sanctum issues API token

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Client stores token

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Client sends API requests with token

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Sanctum authenticates token

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Server processes request or denies access

The client logs in, Sanctum checks credentials and gives a token. The client uses this token to access protected API routes, and Sanctum verifies the token each time.

Execution Sample

Laravel

Route::post('/login', function (Request $request) {
  $user = User::where('email', $request->email)->first();
  if (! $user || ! Hash::check($request->password, $user->password)) {
    return response()->json(['message' => 'Invalid credentials'], 401);
  }
  $token = $user->createToken('api-token')->plainTextToken;
  return response()->json(['token' => $token]);
});

This code logs in a user by checking email and password, then returns a JSON response with a Sanctum API token if valid.

Execution Table

Step	Action	Input	Check/Process	Output/Result
1	Receive login request	{email: '[e-mail]', password: 'secret'}	Look up user by email	User found with matching email
2	Verify password	Password 'secret'	Compare with stored hash	Password matches
3	Create token	User object	Generate new API token	Token string generated
4	Return token	Token string	Send token in response	Client receives token
5	Client sends API request	API request with token in header	Sanctum checks token validity	Token valid, request allowed
6	Server processes request	Valid token	Execute API logic	Response data sent
7	Client sends API request	API request with invalid token	Sanctum checks token validity	Token invalid, access denied
8	Return error	Invalid token	Send 401 Unauthorized	Client receives error

💡 Execution stops when client receives token or access denied response.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	After Step 7
$request	N/A	{email:'[e-mail]', password:'secret'}	{email:'[e-mail]', password:'secret'}	{email:'[e-mail]', password:'secret'}	{email:'[e-mail]', password:'secret'}	API request with token	API request with invalid token
$user	null	User object found	User object found	User object found	User object found	User object found	User object found
$token	null	null	null	Token string generated	Token string sent	Token string sent	null
$response	null	null	null	null	JSON with token	API response data	401 Unauthorized error

Key Moments - 3 Insights

Why does Sanctum return a plain text token instead of a hashed one?

Sanctum returns a plain text token once so the client can store it. The server stores a hashed version for security. See execution_table step 3 and 4.

What happens if the password check fails?

The code returns a 401 Unauthorized response immediately, stopping token creation. See execution_sample code if condition.

How does Sanctum verify the token on API requests?

Sanctum checks the token sent in the request header against stored hashed tokens. If it matches, access is granted; otherwise, denied. See execution_table steps 5 to 8.

Visual Quiz - 3 Questions

Look at the execution table, what is the output at step 3?

A User object found

B Token string generated

C 401 Unauthorized error

D Password mismatch

💡 Hint

Check the 'Output/Result' column at step 3 in the execution_table.

At which step does Sanctum deny access due to an invalid token?

A Step 7

B Step 6

C Step 5

D Step 4

💡 Hint

Look for 'Token invalid, access denied' in the execution_table.

If the password is wrong, what will the response be?

A Token string generated

B User object found

C 401 Unauthorized error

D API response data

💡 Hint

See the code in execution_sample, step 2 verification fails.

Concept Snapshot

API Authentication with Sanctum:
- Client sends login with email/password
- Server verifies credentials
- Server returns plain text API token
- Client uses token in Authorization header
- Sanctum verifies token on each API request
- Access granted if token valid, else 401 error

Full Transcript

This visual execution shows how Laravel Sanctum handles API authentication. First, the client sends a login request with email and password. The server looks up the user by email and checks the password. If correct, Sanctum creates a plain text API token and returns it to the client. The client stores this token and sends it with future API requests in the Authorization header. Sanctum verifies the token on each request. If the token is valid, the server processes the request and returns data. If invalid, Sanctum returns a 401 Unauthorized error. This flow ensures secure API access using tokens.