Amazon CloudFront access logs provide detailed information about every user request that CloudFront receives. Starting today, seven additional data fields will now appear in your CloudFront access logs to improve visibility into the delivery of your content. For example, with the x-edge-detailed-result-type field you can identify the specific type of error and with the sc-range-start/sc-range-end fields you can determine the requested range details. These new fields are appended to the end of each log entry to maintain backwards-compatibility with the previous log file format. The seven new data points include:
- c-port – The port number of the request from the viewer.
- time-to-first-byte – The number of seconds between receiving the request and writing the first byte of the response, as measured on the server.
- x-edge-detailed-result-type – When the result type is an error, this field contains the specific type of error.
- sc-content-type – The value of the HTTP Content-Type header of the response.
- sc-content-len – The value of the HTTP Content-Length header of the response.
- sc-range-start – When the response contains the HTTP Content-Range header, this field contains the range start value.
- sc-range-end – When the response contains the HTTP Content-Range header, this field contains the range end value.
Web Distribution Log File Format in the CloudFront documentation.