W3C Extended Log File Format Viewer

What can it do?

W3C Extended Log File Format is a file format specification from the World Wide Web Consortium (W3C) used by multiple web servers like IIS. The format is ASCII based and is split into two parts: metadata and log data. As part of the metadata the log file specify which fields are expected in the log output. Here's a quick example of a log output generated by IIS:

#Software: Microsoft Internet Information Services 10.0
#Version: 1.0
#Date: 2022-06-13 07:55:09
#Fields: date time s-ip cs-method cs-uri-stem cs-uri-query s-port cs-username c-ip cs(User-Agent) cs(Referer) sc-status sc-substatus sc-win32-status time-taken
2022-06-13 07:55:09 ::1 GET / - 80 - ::1 Mozilla/5.0+(Windows+NT+10.0;+Win64;+x64)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/102.0.5005.63+Safari/537.36 - 200 0 0 686
2022-06-13 07:55:09 ::1 GET /iisstart.png - 80 - ::1 Mozilla/5.0+(Windows+NT+10.0;+Win64;+x64)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/102.0.5005.63+Safari/537.36 http://localhost/ 200 0 0 1
2022-06-13 07:55:09 ::1 GET /favicon.ico - 80 - ::1 Mozilla/5.0+(Windows+NT+10.0;+Win64;+x64)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/102.0.5005.63+Safari/537.36 http://localhost/ 301 0 0 1
2022-06-13 07:55:09 ::1 GET /favicon.ico/ - 80 - ::1 Mozilla/5.0+(Windows+NT+10.0;+Win64;+x64)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/102.0.5005.63+Safari/537.36 http://localhost/ 404 0 2 0

The first four lines contain metadata about the server generating these log lines as well as which fields are available for each log line. The line starting with #Fields contains a space-separated list of fields like date and c-ip.

The following lines contain the actual log data. The format of these lines follows the list of fields specified in the #Fields metadata. Getting an overview of these lines using a text editor can be hard since the log data isn't tabular.

Using elmah.io's free W3C Extended Log File Format Viewer you can easily upload a log file and view it in a tabular form. Be aware that log data can contain personal or security-related content that you don't want to share with people outside your organization. The specified log file or content will be uploaded to our servers for processing but not logged or stored outside the scope of the upload request.'