External Link Plugin

This plugin adds a visual indicator to external links, so users can distinguish outgoing links from site links.

This will only work for forced links marked up using the so-called double bracket syntax, like:

[[http://external.site][an external site]] and [[http://external.site]]

URLs that are just written in as http://external.site are left untouched.

Syntax Rules

Remember to use the double bracket link syntax.

Plugin Settings

Change default settings in configure.

Configure setting	Meaning	Default
{MarkerImage}	link marker image; see below for a list of images
{CheckCompletePage}	If set to 1, disables the commonTagsHandler and uses a completePageHandler to check and stylize all external links on the page.	0
{Debug}	If set to 1, writes debugging info to data/debug.txt	0

Marker images

Code text	Image
%PUBURLPATH%/%SYSTEMWEB%/ExternalLinkPlugin/external.gif
%PUBURLPATH%/%SYSTEMWEB%/ExternalLinkPlugin/diagonal.gif

CSS Classes

This plugin adds one CSS class:

.externalLink

link class to mark outgoing links

IDN Considerations

International Domain Names allow use of the UNICODE character set in domain names. This enables a form of spoofing, where an alternate domain name is crafted with characters that appear like your local domain name, but lead to an external site.

Enabling the {CheckCompletePage} setting will check the generated HTML for all links on the page, and will stylize any external link on the page with the external link marker.

Plugin Installation Instructions

You do not need to install anything in the browser to use this extension. The following instructions are for the administrator who installs the extension on the server.

Open configure, and open the "Extensions" section. Use "Find More Extensions" to get a list of available extensions. Select "Install".

If you have any problems, or if the extension isn't available in configure, then you can still install manually from the command-line. See http://foswiki.org/Support/ManuallyInstallingExtensions for more help.

Testing your installation

To test if the plugin is correctly installed, check the following links.

The links in the "If plugin enabled"-column should be marked with a marker if the plugin is functioning correctly.

Code text	If plugin enabled
[[http://foswiki.org][foswiki.org]]	foswiki.org
[[http://foswiki.org]]	http://foswiki.org

Unsurprisingly, local links won't be marked as being external. The following links should not be marked:

Code text	If plugin enabled
[[%ATTACHURL%/bli.png][link to (nonexistent) local attachment]]	link to (nonexistent) local attachment

If you have enabled the {CheckCompletePage} option in the configuration, then the following html links will also be checked:

Code text	If {CheckCompletelPage} enabled
<a href='http://foswiki.org'>foswiki.org</a>	foswiki.org

But local links will not be marked external:

Code text	If {CheckCompletelPage} enabled
<a href='https://foswiki.org/pub/System/ProjectLogos/foswiki-badge.png'>logo</a>	logo

Plugin Info

Authors:	TWiki:Main.AurelioAHeckert, TWiki:Main.NelsonFerraz, TWiki:Main.AntonioTerceiro, Foswiki:Main.ArthurClemens
Change History:
01 Aug 2015	v1.30 - Foswikitask:Item8446: Don't nest externalLink spans Foswikitask:Item8563: Recognize short URLs as internal links. Foswikitask:Item13590: Update for Foswiki 2.0, test with utf-8 international links. Check [<nop[...]] forced links to detect idn based spoofing attacks. Add optional completePageHandler to process all html links.
31 Dec 2009	v1.21 - fixed closing css declaration.
02 Oct 2009	v1.20 - Ported to Foswiki; changed img HTML tag to CSS style; moved plugin settings to Configure.
24 Apr 2006	v1.11 - %TOPIC% removed from =MARK definition, wasn't expanded correctly.
23 Apr 2006	v1.10 - Incorporated patch from TWiki:Main.TobiasRoeser (only mark external link once in an included scenario). Minor doc brush-up. Changed default marker to external.gif graphic. (TWiki:Main.SteffenPoulsen).
02 Nov 2005	v1.00 - Initial release