HTTP 306 "Unused" Code: Irrelevance, Alternatives, and Recommendations

The non-standard 306 "Unused" server response code was intended to be used in the HTTP protocol to indicate to a client that a specific proxy server should be used. However, as the protocol developed and its standardization, code 306 was considered irrelevant and is not recommended for use in modern web applications and services.

The reason for not using the 306 code was that not all browsers, clients, and search engines supported the code, which resulted in unpredictable behaviour when used. Instead of 306, it is recommended to use other standard server response codes, such as 301 (Moved Permanently) or 302 (Found), to redirect requests to other addresses.

These codes are widely supported and provide more reliable and consistent behaviour for web applications and clients when redirecting requests.

Discover more about 3xx response codes in our article "3xx Redirect Statues: Understanding, Causes and Solutions."

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1. HTTP Status Codes: The Complete List
2. 3xx Redirect Status Codes
3. Status Code 300 - Multiple Choices
4. Status Code 301 - Moved Permanently
5. Status Code 302 – Found
6. Status Code 303 - See Other
7. Status Code 304 - Not Modified
8. Status Code 305 - Use Proxy
9. Status Code 307 - Temporary Redirect
10. Status Code 308 - Permanent Redirect