OCLC Openly Informatics :Link Evaluator

Link Evaluator

a Firefox extension for evaluating links and linked content. Download it now!

  1. Overview
  2. Technical Requirements, License Information
  3. Installation Instructions
  4. How to Use
  5. Editing the Red/Green-flag Phrases
  6. Profiles
  7. Link Background Colors - explanation
  8. Using Link Evaluator with special "Link Evaluator-aware" content online


Link Evaluator is a Firefox extension designed to help users evaluate the availability of online resources linked to from a given Web page. When started, it automatically follows all links on the current page, and assesses the responses of each URL (link).

Link Evaluator examines both the HTTP status code and the page contents returned by each URL, and attempts to distinguish between various results such as:

  • broken links (404)
  • network time-outs
  • authentication failure, and
  • "incorrect" content for the given URL.

After each link is checked, it is highlighted with a color based on the relative success of the result: green for fully successful, shades of yellow for partly successful, and red for unsuccessful.

Link Evaluator is capable of detecting "red-flag" and "green-flag" phrases embedded in Web content specifically for checking links, i.e. text that is likely to indicate a Web page has been successfully reached or not. You can also edit the sets of red- and green-flag phrases to be used.

You can also create special "Link Evaluator-aware" test pages in which the test phrases for each resource are embedded right in the HTML. For example, a library could create a page of test links for its particular set of electronic resources, and then add test phrases to the page, so that all the library's resources can be accurately evaluated at any later point, by simply running Link Evaluator on this test page.

You can also use Link Evaluator to test all of your bookmarked links at once (new feature added January 2007).

Technical Requirements, License Information

Link Evaluator is designed for Mozilla Firefox version 1.5 and later.

The extension and accompanying materials are (c) Copyright 2006 OCLC Online Computer Library Center, Inc. Licensed under the Apache License, Version 2.0 (the "License"); you may not use this material except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, materials distributed under the License are distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Installation Instructions

  1. Click here to download the externsion (links to addons.mozilla.org).
    Note that your browser security settings may cause the download to be blocked. In this case, you must edit your settings to allow downloads from this site.
  2. If Firefox brings up an installation prompt, click "Install". If it asks you if you want to open or save the file, open the file with Firefox as the application. Alternatively, you can save the file to disk and drag it on to the Firefox window.
  3. Quit (exit) the browser, then restart. The extension will then be installed.

How to Use

Starting the Link Evaluator tool

First, point your browser to a Web page whose links you wish to test. For example, you could use Link Evaluator Examples Page.

Then, run Link Evaluator, using any of these three methods:

  1. Go to your browser's "Tools" menu, select "Link Evaluator", and then select "Evaluate Links" from the sub-menu;
  2. On any Web page, right-click anywhere on the page (or for Mac users, control-click), and select "Evaluate Links" from the context menu; or
  3. Select "Start" in the Monitor section of the Link Evaluator Control Panel (see below). 

Using Link Evaluator to test your bookmarks:

You can test all of your bookmarked pages at once with Link Evaluator.  To do this, go to your browser's "Tools" menu, select "Link Evaluator", and then select "Evaluate bookmarks in a new tab" from the sub-menu.

Opening the Link Evaluator Control Panel

The Control Panel is used to change preferences, view results, and as an alternate way to start/stop Link Evaluator. (note: this is not the same as the the Windows XP Control Panel tool reached from the Windows Start menu).

To open Control Panel, either

  1. select from your browser menu "Tools > Link Evaluator > Link Evaluator... "; or
  2. right-click anywhere on a Web page (Option-click for Mac users), and select "Link Evaluator..." from the context menu.

The popup panel contains the following four sections:

  • "Red/green-flag phrases",
  • "Monitor",
  • "Help",
  • "About"

the first section is for customization (see next sections), the next tab (monitor) can be used to start and stop the link testing and to see the log of the tests.

Viewing Results and Halting Link Evaluator:

The results of page evaluation, during or after Link Evaluator runs, can be viewed in the Monitor area of the Control Panel.

Also, a test progress indicator appears in the right side of your browser's status bar while Link Evaluator is running. (note that the status bar may not display if it is turned off in your browser. Go to View > Status Bar in your browser menu to turn on).

You can halt Link Evaluator while it is running by double-clicking on this status indicator.

Also, if you roll over (mouse over) the link, text will appear noting the HTTP status found for that link, and also any "green-flag" or "red-flag" phrases found in the page content. (see Editing the Red/Green-flag Phrase below for more about flag phrases).

Editing the Red/Green-flag Phrases

Link Evaluator examines the content returned by each URL for the presence of certain "green-flag" and "red-flag" phrases. These are words or phrases which are known to often indicate successful or failed links: for example, "Table of contents" or "Not found."

You can view, edit or add to the set of phrases used, by going to the "Red/green-flag phrases" area of the Control Panel. There are two colored sections there - red and green.

In each of these sections there is a default set of phrases, with each line of text representing a unique phrase. You can edit, remove, or add to the set of phrases. Select "Activate" to use them the next time you perform test with Link Evaluator.. At any time during the edit process, you can reload the active set of phrases, by selecting "Read active."


The user can create and store named sets of red- and green-flag phrases, i.e. test profiles. There is one built-in profile (more will be added later). Each profile contains a set of red-flag and a set of green-flag phrases.

A drop-down box in the "Red/green-flag phrases" area of the Control Panel, shows the currently available profiles. Choosing "New profile" would activate a prompt asking to give it a name. Then you may edit the content of the red and green boxes inside that section.

There is a modify/save button, that would save the current content of the red and green boxes under the currently chosen profile name.

After editing or reloading a phrase set, you must click on "Activate" for this set to be used the next time you run Link Evaluator.

Note that the Red-flag set and the Green-flag set each have their own "Activate" buttons, you must click on both to activate after loading a new profile.

Link Background Colors - explanation

After a link is tested, Link Evaluator changes the background color behind the link to indicate the "score", or degree of success, found during the evaluation.

The link background will turn RED If the link failed, or if mostly red-flag phrases were found in the response. It will turn GREEN if the link returned an "OK" status code and green-flag phrases.

If a mixture of results is found, then the link background will be given a color somewhere between red and green on the RGB scale, ranging from reddish-yellow (orange), to yellow, to green-yellow.

Using Link Evaluator with special "Link Evaluator-aware" content online

Link Evaluator is capable of detecting red- and green-flag phrases that have been embedded in special Web content for testing purposes. This "Link Evaluator-aware" content can contain flag phrases that are to be applied only to specific links or ranges of links.

So, you can create smart test pages on which you add words or phrases which you know to be present on successfully retrieved pages for a given URL or group of URLs.

To create such content, simply place DIV elements into your HTML content above the links to be tested, describing the flag phrase to be used.

For example, to set a red-flag phrase of "access denied" and a green-flag phrase of "billion items" for the WorldCat.org web site:

<div class="linkval_FP_red" title="access denied">
<div class="linkval_FP_green" title="billion items">
<a href="http://www.worldcat.org">

See the Link Evaluator Examples Page for more information and example test links.

Contact Us

OCLC Openly Informatics
2 Broad St.
Suite 208
Bloomfield NJ 07003
tel: 1-973-509-7800