Write alt text for the purpose an image serves in its particular setting. For a simple informative image, give the meaning someone needs in a short description. For an image that acts as a link or button, communicate the destination or action. A purely decorative image can have an empty alternative.
Start by asking what the reader would miss if the image were unavailable. Then check whether that information already appears in the surrounding text. W3C's informative-image guidance makes purpose and context central to choosing the alternative.
This guide uses the bridge illustration below as a writing exercise. The other placements we consider are hypothetical.
Describe the image's job in its setting
The bridge illustration used for the editing exercise below.
The illustration shows an amber glass bridge connecting two ivory page cards on separate stone supports. In this article, the scene is the subject of an editing exercise, so those visible objects matter. A concise description is: “Amber glass bridge connecting two ivory page cards.”
Now imagine using that same artwork in a guide about internal links. Its purpose would be to illustrate a connection between related pages. The description could express that relationship rather than inventory the stone, glass, lighting, and background.
W3C's informative-image tutorial explains that the alternative should convey the image's relevant meaning, which may differ from a literal visual description. That leaves the writer with an editorial decision: what information does this reader need here?
Compare four possible placements
| Placement of the bridge artwork | Suitable alternative | Reason |
|---|---|---|
| The visual editing exercise in this article | Amber glass bridge connecting two ivory page cards. | The visible scene is what we are describing and revising |
| An illustration explaining internal links | A bridge between two page cards illustrates a connection between related pages. | The relationship is the point of the metaphor |
| The only content of a link to the internal-linking guide | Read: How to build internal links that help readers. | The reader needs to know where the link goes |
| An unlinked visual flourish whose meaning is fully covered nearby | An empty alt value | The image adds no separate information in that assumed placement |
These are different editorial uses, rather than four descriptions competing for a universal “best” score. A description suitable for the first placement could be unhelpful in the third.
For a linked image, follow W3C's functional-image guidance: communicate the function. The example link would lead to our guide on building internal links that help readers. Describing amber glass alone wouldn't explain that destination.
Also distinguish an image-only link from an image that shares a single link with a clear written title. W3C shows that a redundant image in the latter arrangement can have an empty alternative when the link text already supplies its purpose. A title somewhere else on the page doesn't automatically label a separate image-only link.
Remove details that don't help the reader
For the bridge example, “beautiful warm sunlight on a premium travertine platform” describes the styling but delays the useful relationship. Those details could matter in an article evaluating the visual design. Here, the connection between two page cards is more relevant.
Revise in two passes. First, include the information needed to understand the image's role. Then remove words that don't change that understanding.
For example:
- Too vague: Bridge.
- Cluttered: A beautiful amber bridge in bright golden sunlight on pale textured stone, with cards, shadows, and a warm background.
- Useful for this exercise: Amber glass bridge connecting two ivory page cards.
The last version preserves the objects and their relationship. Its value comes from that choice, rather than reaching a particular character count.
Keep interpretations within what the image supports. “Internal links doubled traffic” would turn a conceptual bridge into an unsupported result. When an illustration represents an idea, name the idea without presenting the artwork as evidence that an intervention worked.
This is the same distinction between a claim and its support discussed in our guide to what makes a page worth citing.
Keep essential explanations in visible text
A conceptual illustration pairing a visual route with a written explanation.
Some images contain more information than a short alternative can carry. A chart might encode values, units, comparisons, and a trend. An instructional diagram might show a sequence whose order matters.
W3C's complex-image guidance describes a two-part approach: a short identification of the image and a fuller text equivalent of the essential information. The short alternative can indicate where to find that longer explanation.
For a hypothetical chart, an alternative might identify the topic and point to a clearly named table below it. The table and nearby explanation would then supply the actual values, units, and relevant relationships. Only refer to a table or section that exists and is easy to locate.
For a process diagram, write the sequence in the article as well. Keep branch conditions and exceptions with the steps they affect. Someone should be able to complete the explanation from the text, without having to infer missing instructions from the picture.
The route illustration in this section is conceptual. It contains three connected waypoints, but no real locations or measured data. It calls attention to the relationship between a visual explanation and its written companion; it shouldn't be described as a customer journey we observed.
Give words inside images an alternative too
If an image conveys essential written words, make those words available in text. W3C's images-of-text guidance says the alternative should contain the words presented in the image. Its guidance also favors ordinary text where possible.
For a blog cover with a headline, keep the article title as a normal page heading too. For an instruction graphic, put the instructions in the body. Then evaluate the image in that surrounding context, including whether any unique information remains.
A caption can help everyone understand an illustration, state a source, or point to a full explanation. Check it together with the image alternative so each has a clear job. Repeating the same long description in every place adds words without necessarily adding information.
Use an empty alternative deliberately
A decorative image adds no separate information in its setting. W3C's decorative-image guidance recommends an empty alt value, written as alt="", for such images. Leaving the attribute out is different: some screen readers may announce the filename instead.
The decision depends on the placement. Our bridge is useful as the object of this writing exercise. If it were reused only for visual atmosphere beside text that already supplies everything it conveys, that other use could be decorative.
Don't classify an image as decorative simply because it was generated, looks polished, or has a metaphorical subject. Ask whether it contributes information or performs an action. Conversely, a photograph doesn't automatically need a detailed description if it serves only a decorative role.
If your publishing tool has a “decorative image” option, check what it produces on the page. An empty text field in the editor may not tell you whether the published image has an empty alternative, a missing attribute, or an automatically inserted filename.
Let the context guide the SEO wording
Google's image SEO guidance says it uses alt text alongside computer vision and page content to understand an image. It also recommends useful wording in context and warns against keyword stuffing.
For the bridge scene, “SEO agency content marketing internal links AI visibility ranking optimization” supplies a list of topics without explaining the image. A description of the connection between the page cards is more useful.
Use the subject's proper name when identifying it matters. Include a relevant term naturally when it describes what the reader needs. Don't attach every keyword from the article plan to every illustration.
Also keep the image near the passage it helps explain. Google includes surrounding content and captions among its sources of image context. For readers, that placement gives the visual and its explanation a shared setting.
Review the published image and its description together
Review the image, its role, and its alternative in the same context.
Save a short note for each important image: where it appears, what it contributes, whether it is linked, and the proposed alternative. That record makes later reuse easier to review.
After publishing, inspect the actual image and its alt attribute. Check that the CMS saved the intended wording. If the image is a link, follow it and confirm that the description communicates the real destination. If the description refers to a table or heading, locate that content on the page.
Read the heading, paragraph, caption, and alternative together. Look for a missing relationship, unnecessary repetition, a claim the visual doesn't support, or an instruction that still depends on seeing the image.
Repeat that review when you replace the artwork or move it into a different role. A previously accurate alternative can become wrong even when the image file itself hasn't changed.
For the bridge, the practical decision is clear: describe its visible connection in this exercise, describe the relevant concept in an explanatory article, and name the destination when it becomes an image-only link. The writing follows the reader's task.
References
- W3C Web Accessibility Initiative: Informative images.
- W3C Web Accessibility Initiative: Functional images.
- W3C Web Accessibility Initiative: Decorative images.
- W3C Web Accessibility Initiative: Complex images.
- W3C Web Accessibility Initiative: Images of text.
- Google Search Central: Image SEO best practices.