multiValueHeaders

multiValueHeaders is a concept primarily found in certain HTTP request and response processing environments, particularly those used in API gateways or serverless computing platforms. It refers to the ability for a single header field to contain multiple values. In standard HTTP, most headers are expected to have a single value. However, some headers, by their nature or by convention, can have multiple occurrences or a comma-separated list of values.

When a system supports multiValueHeaders, it means that when processing an incoming HTTP request, if a header like "Set-Cookie" or "X-Forwarded-For" appears multiple times, the system can correctly capture and represent all of those individual values. Similarly, when constructing an outgoing HTTP response, the system can allow for the inclusion of multiple values for a single header field. This is often handled by storing these headers as an array or list associated with the header name, rather than a single string. This distinction is important for applications that need to precisely parse and interpret all transmitted header information. Without support for multiValueHeaders, duplicate headers might be ignored, or their values might be concatenated into a single string, potentially leading to data loss or misinterpretation.