Content negotiation in Rest API - Step-by-Step Execution

Concept Flow - Content negotiation

Client sends HTTP request with Accept header

↓

Server reads Accept header

↓

Server checks supported content types

↓

Match found?

No→Send 406 Not Acceptable

Yes↓

Server sends response in matched content type

The client requests a specific content type via the Accept header; the server checks if it supports it and responds accordingly or sends an error.

Execution Sample

Rest API

GET /data HTTP/1.1
Host: example.com
Accept: application/json

--- Server checks Accept header ---
If 'application/json' supported:
  Respond with JSON data
Else:
  Respond 406 Not Acceptable

This example shows a client requesting JSON data and the server responding with JSON if supported.

Execution Table

Step	Action	Accept Header	Server Supported Types	Match Found?	Server Response
1	Client sends request	application/json	application/json, text/html	Yes	Waiting for server processing
2	Server reads Accept header	application/json	application/json, text/html	Yes	Checking supported types
3	Server finds match	application/json	application/json, text/html	Yes	Prepare JSON response
4	Server sends response	application/json	application/json, text/html	Yes	200 OK with JSON data
5	Client sends request	application/xml	application/json, text/html	No	Waiting for server processing
6	Server reads Accept header	application/xml	application/json, text/html	No	Checking supported types
7	Server finds no match	application/xml	application/json, text/html	No	Send 406 Not Acceptable

💡 Execution stops after server sends response or 406 error based on content negotiation

Variable Tracker

Variable	Start	After Step 1	After Step 3	After Step 4	After Step 5	After Step 7
Accept Header	None	application/json	application/json	application/json	application/xml	application/xml
Server Supported Types	application/json, text/html	application/json, text/html	application/json, text/html	application/json, text/html	application/json, text/html	application/json, text/html
Match Found?	No	Yes	Yes	Yes	No	No
Server Response	None	Waiting for server processing	Prepare JSON response	200 OK with JSON data	Waiting for server processing	406 Not Acceptable

Key Moments - 3 Insights

Why does the server send a 406 Not Acceptable response?

Because the Accept header requests a content type the server does not support, as shown in execution_table rows 5-7 where 'application/xml' is not matched.

What happens if the Accept header is missing?

The server usually sends a default content type response, but this example assumes Accept header is present; without it, server picks a default supported type.

Can the Accept header list multiple types?

Yes, the Accept header can list multiple types with priorities; the server picks the best match from its supported types.

Visual Quiz - 3 Questions

Look at the execution_table, what is the server response at step 4?

A 200 OK with JSON data

B 406 Not Acceptable

C Waiting for server processing

D Prepare XML response

💡 Hint

Check the 'Server Response' column at step 4 in execution_table

At which step does the server determine no matching content type is found?

A Step 3

B Step 6

C Step 7

D Step 2

💡 Hint

Look for 'Match Found?' = No and 'Server Response' = 'Send 406 Not Acceptable' in execution_table

If the client changes Accept header to 'text/html', what would be the server response?

A 406 Not Acceptable

B 200 OK with HTML data

C 200 OK with JSON data

D Waiting for server processing

💡 Hint

Server supports 'text/html' as per 'Server Supported Types' in variable_tracker

Concept Snapshot

Content negotiation lets clients tell servers what data format they want using the Accept header.
Server checks if it supports the requested type.
If yes, server sends data in that format.
If no, server sends 406 Not Acceptable error.
This helps clients get data they can understand.

Full Transcript

Content negotiation is a process where a client sends an HTTP request with an Accept header specifying the desired content type, such as application/json. The server reads this header and compares it to the content types it supports. If the server supports the requested type, it responds with data in that format and a 200 OK status. If not, it responds with a 406 Not Acceptable error. This process ensures clients receive data in a format they can handle. The execution table shows steps where the server reads the Accept header, checks for matches, and sends the appropriate response. Variables like Accept Header, Server Supported Types, Match Found, and Server Response change during these steps. Common confusions include why a 406 error is sent and what happens if the Accept header is missing or lists multiple types. The visual quiz tests understanding of these steps and responses.