Header-based versioning in Rest API - Step-by-Step Execution

Concept Flow - Header-based versioning

Client sends HTTP request

↓

Check 'Accept' header for version

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Match version in server code

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Process request with matched version

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Send response back to client

The client sends a request with a version in the header; the server reads it, matches the version, processes accordingly, and responds.

Execution Sample

Rest API

GET /api/resource HTTP/1.1
Host: example.com
Accept: application/vnd.example.v2+json

Client requests version 2 of the API resource using the Accept header.

Execution Table

Step	Action	Header Checked	Version Found	Server Behavior
1	Receive request	Accept: application/vnd.example.v2+json	v2	Proceed with version 2 logic
2	Process request	N/A	v2	Use v2 data format and rules
3	Send response	N/A	v2	Respond with v2 formatted data
4	End	N/A	N/A	Request completed

💡 Request ends after response is sent using the matched version logic.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
request_headers	{}	{Accept: 'application/vnd.example.v2+json'}	{Accept: 'application/vnd.example.v2+json'}	{Accept: 'application/vnd.example.v2+json'}	{Accept: 'application/vnd.example.v2+json'}
api_version	null	v2	v2	v2	v2
response_data	null	null	v2 formatted data	v2 formatted data	v2 formatted data

Key Moments - 3 Insights

How does the server know which API version to use?

The server reads the 'Accept' header in the request (see execution_table step 1) to find the version string like 'v2'.

What happens if the 'Accept' header is missing or has no version?

The server may default to a base version or return an error; this is not shown here but would happen before processing (before step 2).

Why use header-based versioning instead of URL versioning?

Header-based versioning keeps URLs clean and allows clients to specify versions without changing endpoints, as shown by the version in the 'Accept' header.

Visual Quiz - 3 Questions

Look at the execution_table, what version does the server detect at step 1?

A v1

B v2

C v3

D No version

💡 Hint

Check the 'Version Found' column in execution_table row for step 1.

At which step does the server prepare the response data in the correct version format?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at the 'Server Behavior' column for when data is formatted.

If the client sent 'Accept: application/vnd.example.v1+json', how would the 'api_version' variable change after step 1?

A It would be 'v1'

B It would be 'v2'

C It would be null

D It would be 'v3'

💡 Hint

Refer to variable_tracker for 'api_version' after step 1 and imagine the header value changed.

Concept Snapshot

Header-based versioning uses HTTP headers (like 'Accept') to specify API version.
Client sends version info in headers.
Server reads header, matches version.
Server processes request using matched version logic.
Response is sent in requested version format.
Keeps URLs clean and flexible.

Full Transcript

Header-based versioning means the client tells the server which API version it wants by sending a special header, usually the 'Accept' header. The server looks at this header to find the version number, like 'v2'. Then the server uses that version's rules to handle the request and sends back the response in the right format. This way, the URL stays the same, and the version is controlled by headers. In the example, the client sends 'Accept: application/vnd.example.v2+json', so the server uses version 2 logic. The execution table shows each step: receiving the request, checking the header, processing with version 2, and sending the response. Variables like 'api_version' track the version found. This method helps keep APIs clean and flexible.