HTTP 3xx codes indicate that the requested resource has moved and the client must follow a redirect using the URL provided in the Location header. 3xx status codes maintain backward compatibility with older endpoints by enabling smooth redirection without client-side failures, improving overall API maintainability and long-term stability.
HTTP 3xx responses are commonly encountered during:
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API version upgrades
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URL and endpoint restructuring
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Authentication and authorization flows
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Performance optimization through caching
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301 – Moved Permanently
The resource has been permanently moved to a new URL, and clients should use this new URL for all future requests.
ExampleGET /api/v1/users → GET /api/v2/users
Key Points
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Permanent change
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Old URL should no longer be used
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HTTP method may change (POST can become GET)
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Common during API version upgrades
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302 – Found (Temporary Redirect)
The resource is temporarily available at another URL, while the original URL remains valid.
Example
Traffic redirected to a temporary service during maintenance.
Key Points
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Temporary redirection
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Original URL still works
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Method may change
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Not recommended for critical POST APIs
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303 – See Other
Instructs the client to fetch the response using a GET request at a different URL, even if the original request was POST.
ExamplePOST /orders → GET /orders/{orderId}
Key Points
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Converts POST to GET
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Prevents duplicate submissions
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Common after form or order creation
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Improves user experience
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304 – Not Modified
The requested resource has not changed, so the client can use the cached version.
Example
Browser or client sends If-Modified-Since, server returns 304.
Key Points
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No response body
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Improves performance
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Reduces network usage
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Used with caching headers
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307 – Temporary Redirect
The resource is temporarily moved to another URL while preserving the original HTTP method and request body.
ExamplePOST /payments redirected to a temporary payment service.
Key Points
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Temporary redirection
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Method and payload preserved
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Safer than 302 for POST APIs
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Used in microservice routing
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308 – Permanent Redirect
Indicates that the requested resource has been permanently moved to a new URL without changing the HTTP method or request body.
Scenario: HTTP → HTTPS Migration
Request (Old URL):POST http://api.example.com/orders
Response:
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Status Code: 308
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Location: https://api.example.com/orders
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Behavior:
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Client retries the request to the HTTPS URL
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POST method is preserved
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Request body and headers remain unchanged
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Nithyarani is working as Senior QA analyst in Knowillence. She has over 10 years of experience working as QA. She has worked extensively in the retail domain and has automated API testing, DB testing and Web Application testing using various testing tools. She is proficient in Agile project management as well and manages the requirements and change requests in projects very well.