Summary

  • HTML 3.2 called IMG alt vital for speech-based and text-only agents, but its DTD marked the field #IMPLIED; AREA alt was #REQUIRED.
  • HTML 4.0 required alt on both elements, then WCAG 1.0 broadened the rule to text equivalents for every non-text element.

Analysis

The oddity sits inside one Recommendation. HTML 3.2 describes the IMG alt attribute as vital for interoperability with speech-based and text-only user agents. Its DTD, the grammar a validator could enforce, says something softer: src is #REQUIRED; alt is #IMPLIED. An image could pass that grammar without the very text the prose had just praised. The standard states the purpose, but does not explain why it stopped short of requiring the field.

The split was already present in HTML 2.0. RFC 1866, published in November 1995, says a user agent may process ALT as an alternative to the resource named by SRC. Its DTD also makes IMG alt #IMPLIED. HTML 3.2, dated 14 January 1997, aimed to capture recommended practice from early 1996; it kept the optional grammar while making the interoperability case more emphatically. Strong advice and a machine-checkable rule were traveling on separate tracks. (RFC 1866; HTML 3.2)

Then look at AREA, the element for a clickable region inside an image map. HTML 3.2 marks each AREA alt #REQUIRED and comments that it is needed for non-graphical user agents. The prose explains the practical shape: these labels can form a text menu of the map’s hotzones. The same DTD that let an image arrive without a label refused to let one of its clickable regions do so. The documents establish the contrast; they do not establish the authors’ motive.

  • HTML 4.0 Recommendation (18 December 1997)
  • HTML 4.0 Strict DTD HTML 4.0, recommended on 18 December 1997, moved IMG into the stricter column: alt is #REQUIRED for both IMG and AREA, and authors must supply it. But a required field is not automatically a long description. HTML 4.0 says an empty string is appropriate when an image serves only to format the page. The rule checks that a choice was made; the author still has to choose well. (HTML 4.0: images and objects)

WAI’s March 1999 Techniques document mapped the options by HTML version. It described alt as mandatory for IMG and AREA in HTML 4.0, available for more elements in HTML 3.2, and available for IMG in HTML 2.0. For older formats whose user agents could not handle those attributes, it recommended putting the equivalent in the text or linking to a fuller description. Two months later, WCAG 1.0 checkpoint 1.1 called for a text equivalent for every non-text element and gave it Priority 1. At Level A, every Priority 1 checkpoint had to be met. The obligation had widened from one attribute to the information carried by non-text content. (WAI Techniques, 24 March 1999; WCAG 1.0)

The practical boundary is plain: prose can name a need, a DTD can reject a missing field, and an authoring checkpoint can cover content beyond one tag. None of those steps proves that a supplied description says what the image does. To measure what readers encountered, we need dated page samples paired with browser and speech-agent support records; those records would establish omission and implementation rates.

Sources