User Agents and longdesc Discoverability

Innovative browser vendors and developers provide ways that make longdesc discoverable to sighted users. These include:

Global Icon

Opera's TellMeMore extension provides an icon in the chrome to indicate when descriptions exist. The user is notified by the icon changing from an inactive state greyed-out, lined-through iconto active state vibrant-colored, 'open-eye' iconand presenting a title.

Screenshot of activating a description icon in a browser's chrome

Upon activating the icon, the user is presented with a popup containing a list of all descriptions available along with their thumbnail images.

Screenshot of popup list, displayed over an image, containing a 'long description' menu items.

Then when the user selects a link in the popup, a new tab is opened with a text description in it.

Note: a variation on this method is a Yandex extension, which provides the icon in the address bar rather than the chrome.

Context Menu

iCab, Opera 1010b1 to Blink, and as of Mozilla 25 FireFox all have native support via the image context menu. Support for prior versions of Mozilla is suppiled via Longdesc Firefox Extension. A Chrome plugin by Chris Kennish highlights and provides right-click access to image long descriptions. IE can be configured to add context menu. In addition iCab provides users a visual clue by changing cursors from a standard cursor to a special contextual-menu cursor upon encountering an image with a long description.

Screenshot of a context menu, displayed over an image, containing a 'long description' menu item.

Direct Replacement

A user agent could allow users to navigate browsing contexts to the resource, or replace images with their long text alternatives according to user preference.

Screenshot of a preference panel with 'Display Image Descriptions' selected.

If a "Display Image Descriptions" preference is selected by a user, a user agent could then superimpose an icon or button directly on or beside the image itself whenever descriptions are available.

Screenshot of an icon superimposed directly on an image.

Upon activating the icon or button the image could disclose the description in addition to the image or it could replace the image with the description.

Screenshot of a longdesc text in an iframe.

This type of direct replacement functionality is provided in a scripted longdesc implementation. The preference panel image is an adaptation of iCab's preferences panel.

Tools such as FireFox's Longdesk extension and Jim Thatcher's universal longdesc favelet make longdesc discoverable to sighted users via on-page links.


FireFox's Longdesk Extension by Anthony Ricaud adds a link to the longdesc under images that have a longdesc attribute. A user agent could allow users who want an image description link on screen this option according to user preference.

Screenshot of longdesc as a link.

Long Description Favelet

A powerful and universal longdesc favelet by James Thatcher first announces the number of images on the page that have longdesc attributes.

Screenshot of longdesc alert.

Then it highlights each image on the page that has a longdesc and provides on-screen text links to each corresponding description.

Screenshot of images highlighted and corresponding longdesc links.

For the functional favelet drag longdesc to your bookmarks. Tested in Chrome, FireFox, Internet Explorer, Safari, Opera, and iCab.


Chris Kennish's longdesc chrome plugin is an example of providing a long description according to user choice while not forcing a visual encumbrance upon them. Once the extension is installed the user is provided with the following customization preferences.

Highlight Color

Highlight style

Highlight width

Open longdesc

Touch Device Methods

Touch device activation could be upon:

A touch User Interface ( UI ) could utilize a "turn the image around" transition e.g., the UI could have a flip transition akin to flipping over a hard-copy physical photograph to read what is written on the back.