HTTP Status Codes Explained for API Testing | 2XX, 4XX, 5XX | For QA Beginners | Part 8
In this video, we will deeply understand HTTP Status Codes used in API Testing, explained from a QA / Tester perspective with real-time examples.
This video answers questions like:
What is a client-side error?
What is a server-side error?
When should a QA report a 4XX or 5XX issue?
How do HTTP status codes work in real applications like shopping apps?
📌 WHAT YOU WILL LEARN IN THIS VIDEO
🔹 What is Client and Server in API Testing
Client = Postman / Browser / Mobile App / User
Server = Backend application handling the request
✅ 2XX – SUCCESS RESPONSES (Request Worked)
These codes mean everything is working fine.
200 OK
Request succeeded and response body is returned
👉 Example: GET product list successfully
201 Created
New resource created successfully
👉 Example: POST – product created
204 No Content
Request successful but no response body
👉 Example: DELETE operation
🧠 As a QA, 2XX means your API is behaving correctly.
❌ 4XX – CLIENT-SIDE ERRORS (Mistake from Client Side)
👉 Client = US (Postman, App, User)
If client sends wrong data, server responds with 4XX.
🔴 400 – Bad Request
Server understood the request but data is invalid
When it happens:
Mandatory fields missing
Wrong data type (string instead of number)
Invalid JSON format
Validation rules failed
📦 Example:
Price sent as "price": "abc"
JSON missing a closing brace { }
📢 Important QA Note:
Even though 400 is client-side,
👉 If request looks correct and error still happens, REPORT IT.
🔴 401 – Unauthorized
Authentication is missing or invalid
When it happens:
Token not sent
Expired token
Wrong credentials
👉 Example: Accessing secured API without Bearer Token
🔴 403 – Forbidden
You are authenticated but NOT allowed
When it happens:
Token exists but user lacks permission
Accessing admin API as normal user
🔴 404 – Not Found
Requested resource does not exist
When it happens:
Wrong endpoint
Wrong ID
Typo in URL
🛒 Real-world example:
Searching a product that doesn’t exist
🔴 405 – Method Not Allowed
HTTP method is not supported
When it happens:
Using POST instead of GET
Using DELETE on a read-only API
🚨 5XX – SERVER-SIDE ERRORS (Server Problem)
👉 Client sent correct request, but server failed.
🔥 500 – Internal Server Error
Code crash
Null pointer
Unhandled exception
🔥 502 – Bad Gateway
One server didn’t get response from another server
🔥 503 – Service Unavailable
Server down
Maintenance
High traffic
📢 QA Rule:
👉 Always report 5XX errors — they are NOT client mistakes.
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