Alternative text is a short textual description attached to an image, icon or other non-text content. It is read by screen readers and used when the image cannot be displayed, and it can also be stored in HTML or document metadata to make content accessible and searchable.
How alternative text works
Alternative text is the textual fallback for non-text content, so its first job is to convey the same essential meaning that the image, icon, chart, or other asset contributes to the page. Good alt text is concise, specific, and tied to the content purpose rather than the visual style.
In practice, alt text is part of the content model, not just a presentation detail. It helps screen readers describe images to blind and low-vision users, and it supports search, indexing, and document portability when the graphic cannot be rendered.
When alt text should be brief, descriptive, or omitted
Not every image needs the same treatment. Informative images usually need a short description of their meaning, while decorative images are often better left empty so assistive technology can skip them without adding noise.
The key judgement is whether the image adds information that the surrounding text does not already provide. If the text nearby already explains the point completely, repeating it in alt text can be redundant and frustrating for users of assistive technology.
Alt text in accessible content workflows
Alt text is usually written by content authors, editors, designers, or developers as part of publishing and review workflows. That makes it a governance issue as much as a writing task, because poor alt text can become a repeatable defect across large content libraries.
For organisations, the practical standard is consistency: define who writes it, when it is required, and how it is reviewed. The same discipline matters in CMS fields, templates, PDFs, email assets, and generated content that includes images or icons.
Common quality issues and how they affect users
Common failures include empty descriptions for meaningful images, vague phrases such as “image” or “graphic,” keyword stuffing, and alt text that describes visual appearance instead of function. These mistakes reduce accessibility and can make navigation harder for screen reader users.
Alt text should also avoid overexplaining. If a caption, surrounding paragraph, or data table already carries the important meaning, the alt text should not duplicate everything. It should identify the purpose of the image and the essential information a user would otherwise miss.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
NIST SP 800-53 Rev 5 and NIST CSF 2.0 set the technical controls, while ISO/IEC 27001:2022 defines the regulatory obligations.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-53 Rev 5 | IA-2 — Identification and Authentication (Organizational Users) | Alt text supports accessible presentation of content to authenticated users across systems. |
| Recommendation — Provide accessible content descriptions wherever users rely on authenticated interfaces to consume non-text information. | ||
| ISO/IEC 27001:2022 | A.5.15 — Access Control | Alt text supports controlled, usable access to information for users who cannot perceive images directly. |
| Recommendation — Ensure published content includes text alternatives so information remains usable across access methods. | ||
| NIST CSF 2.0 | PR.AT-01 — Awareness and Training | Alt text quality depends on authoring discipline and content creator awareness. |
| Recommendation — Train content authors to write concise, meaningful alt text as part of secure and accessible publishing practice. | ||
Practitioner Guidance
Governance implication: Treat alt text as a content quality control, not a last-minute accessibility add-on. Teams should define when an image needs a meaningful description, when it should be decorative, and how editors verify that the text matches the user need rather than the designer’s intent.
What to watch for: The most common review failure is content that sounds descriptive but does not answer why the image is there. A useful test is whether a user who cannot see the asset would still understand the page’s message, action, or data point.
Related resources from NHI Mgmt Group
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Reviewed and updated by the NHIMG editorial team on October 29, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org