|  TWiki External Links URLs starting withfile,ftp,gopher,http,https,irc,mailto,news,nntpandtelnetare linked automatically if preceded by whitespace or parenthesis. External links are indicated with a trailing icon, and open up in a new browser tab or window; the behavior of both can be set in configure or preferences variables. Links can be prevented with an !exclamation point prefix.
Note: if a link is written directly as HTML (<a href="http://...">...</a>), it is not subject to the external link conversion. Preferences Variables Users can customize the behavior of the external links (typically in the WebPreferences page).
The value of
| Variable | Value | Description |  
| EXTERNALLINKSINNEWWINDOW | on/off | Open external links in a new browser tab or window |  
| EXTERNALLINKSICON | on/off | Show a trailing  icon |  
| INTERNALLINKDOMAINS | (see below) | Add domain names that should not be regarded as "external" |  INTERNALLINKDOMAINSis expected to be a comma-separated list of domain names.
Each domain name entry should be any of the below:
If a topic name is specified, the topic is expected to contain a table, where the left-most column is for the domains. A proper domain name (such as www.example.com) - not including any of the subdomains A domain name with a preceding dot (such as .example.com) - indicating any subdomains (e.g.foo.example.com) but not including the domain itself (example.com) A single dot (.) - indicating any "one-word" domain names, typically used in an intranet.
 A topic name in the format topic:TopicNameortopic:WebName.TopicName. The WebName defaults to the base web (%BASEWEB%) in the current context. 
| *Domain* |
| twiki1.example.com |
| twiki2.example.com |
| twiki3.example.com |
  Configuration Administrators can configure the default settings of the external link behaviors. (configure)
See above for the value of
| Config | Default | Description |  
| $cfg{Links}{ExternalLinksInNewWindow} | on | Open external links in a new browser tab or window |  
| $cfg{Links}{ExternalLinksIcon} | on | Show a trailing  icon |  
| $cfg{Links}{InternalLinkDomains} | (unset) | Add domain names that should not be regarded as "external" |  InternalLinkDomains. The WebName in thetopic:TopicNamedefaults to the system web (%SYSTEMWEB%, or "TWiki"). |