How is alternative text attached to an Open Graph image?

Definition: og:image:alt is an Open Graph structured property that attaches a description to the image declared by og:image. The value belongs in the content attribute of a <meta> element whose property attribute is og:image:alt.

Key facts

• The Open Graph protocol specification defines og:image:alt as a description of what is in the image and says a page that specifies og:image should specify og:image:alt.
• The value describes the image itself. The protocol distinguishes it from a caption.
• Open Graph metadata uses <meta> tags in the page <head>, with the property name in property and its value in content.
• The protocol treats og:image:alt as structured metadata attached to og:image, so the image root should appear before its structured properties.
• The HTML standard gives a separate role to the alt attribute on an <img> element: it supplies equivalent content when the image cannot be processed or loading is disabled.

Where does the description go?

The Open Graph page describes its metadata as additional <meta> tags in the document head. For an image, the root property identifies the image URL and the structured property supplies its description. The property attribute names og:image:alt; the content attribute contains the words a consumer can read as the image description.

<meta property="og:image" content="http://example.com/ogp.jpg" />
<meta property="og:image:alt" content="A shiny red apple with a bite taken out" />

The specification describes the value as a description of what is in the image and distinguishes it from a caption. Its full example uses the text “A shiny red apple with a bite taken out.” The page gives no character limit for this property.

Why is og:image required beside it?

og:image:alt is a structured property of the og:image object. The protocol lists og:image as an image URL representing the page object in the graph, then lists og:image:alt among that property's structured properties. Its requirement is conditional: when the page specifies an og:image, the specification says it should specify og:image:alt as well.

This relationship differs from the HTML image element. The HTML Standard says that an <img> element's alt attribute provides equivalent content for people who cannot process images or who have image loading disabled. That attribute is attached to an image element in the page body. og:image:alt is attached to the Open Graph image metadata in the head.

How are multiple Open Graph images handled?

The Open Graph specification allows a page to provide multiple values by repeating the same <meta> tag. It gives preference to the first tag from top to bottom when values conflict. For structured properties, it says to place the property after its root tag and treats another root element as the start of another image group.

For example, an og:image:alt value placed after the first og:image belongs to that image until another og:image starts a new group. The specification's grouping example places og:image:width and og:image:height after the first image, then declares a second og:image.

What does HTML alt add to the distinction?

The HTML Standard describes a non-empty alt value as a textual equivalent or replacement for the image. It also states that an empty alt value can identify a decorative or supplemental image. These rules concern the meaning of an HTML <img> element and its fallback content.

Open Graph's description requirement therefore calls for a separate metadata value even when the page already has an HTML alt attribute. The two fields can describe the same visual, but they belong to different markup systems and their specifications assign them different roles.

Related terms

• Which Open Graph tags are required for a page object?
• How are an Open Graph image's dimensions and format declared?
• Image alternative text

FAQ

Is og:image:alt an HTML alt attribute?

No. It is an Open Graph property on a <meta> element, with the description in content. HTML alt belongs to an <img> element and provides equivalent content when the image cannot be processed.

Should a page include og:image:alt when it has og:image?

Yes. The Open Graph protocol says that a page specifying og:image should specify og:image:alt.

Is the value a caption?

The protocol defines the value as a description of what is in the image and distinguishes that description from a caption.

Where should the tag be placed when several images are declared?

Place the structured property after the og:image root it describes. When another og:image appears, the protocol treats that root as the beginning of another structured-property group.

Sources

1. Open Graph protocol, "The Open Graph protocol", 2025-06-25
2. WHATWG, "HTML Standard, The img element", 2026-10-19

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