astro-aeo-image

An Astro image service that embeds your <Image> alt text (and optional description/keywords/license) as standards XMP/IPTC directly into the optimized output files — so your dist/_astro assets are self-describing: Google Images reads embedded IPTC metadata and recommends embedding it, and the description travels with the file for accessibility, attribution, and the AI-search era.

Astro already requires an alt on every <Image /> — but that text normally lives only in the HTML attribute. The moment the optimized file is downloaded, hot-linked, or indexed as a file, the page context is gone. astro-aeo-image writes the description (and attribution/license) into the image bytes, where it travels with the file.

What's documented: Google Images reads embedded IPTC metadata (creator/credit/copyright/license) and recommends embedding it. For image ranking, Google uses the HTML alt — so embedding complements it (durability, accessibility, attribution), it doesn't replace it or claim a ranking boost. AI engines consuming embedded metadata is forward-looking, not yet a spec.

How it's different from image.service.config.keepMetadata

This is an authoring layer, not a preservation one — and that distinction is the whole point:

| | sharp's keepMetadata / keepExif | astro-aeo-image | | --- | --- | --- | | Carries through metadata already in the source file | ✅ | — | | Authors new descriptive metadata from your app data (the alt you already wrote, captions, keywords) | ❌ | ✅ | | Writes Iptc4xmpCore:AltTextAccessibility + dc:description for AEO/accessibility | ❌ | ✅ |

sharp can preserve a camera's existing EXIF; it can't compose a fresh XMP packet from the alt prop in your .astro file. That's the gap this fills.

How it works

It's a thin wrapper around Astro's own default sharp service. Everything sharp does is unchanged — same resizing, formats, quality, caching. After sharp encodes each variant, this service splices descriptive XMP into the output buffer via aeo-image: byte-preserving, no re-encode — the compressed pixels are identical; only a metadata block is added.

Install

npm install astro-aeo-image

aeo-image comes along as its only dependency (zero-dependency itself). astro is a peer dependency (you already have it).

Configure

Add the integration — one line:

// astro.config.mjs
import { defineConfig } from "astro/config";
import aeoImage from "astro-aeo-image";

export default defineConfig({
  integrations: [
    aeoImage(), // or aeoImage({ useAltAsDescription: false })
  ],
});

// astro.config.mjs
import { defineConfig } from "astro/config";

export default defineConfig({
  image: {
    service: {
      entrypoint: "astro-aeo-image/service",
      config: { useAltAsDescription: true },
    },
  },
});

The integration is just a thin wrapper that sets this for you and forwards options.

That's it. Every <Image /> you already have now ships its alt inside the file:

---
import { Image } from "astro:assets";
import barn from "../assets/barn.jpg";
---
<Image src={barn} alt="A weathered red barn under a violet dusk sky in rural Vermont" width={1200} height={800} />

The generated dist/_astro/barn.*.webp now contains:

• Iptc4xmpCore:AltTextAccessibility = the alt text
• dc:description = the alt text (unless useAltAsDescription: false)

Optional richer metadata

Pass extra props on <Image> for fuller AEO signals (distinct SEO description, keywords, title):

<Image
  src={barn}
  alt="A weathered red barn at dusk"
  description="A restored 1890s dairy barn in Vermont, now a working agrivoltaics site"
  keywords={["barn", "vermont", "agrivoltaics", "rural"]}
  title="Vermont Agrivoltaics Barn"
  width={1200} height={800}
/>

| Prop | XMP field | | --- | --- | | alt (required by Astro) | Iptc4xmpCore:AltTextAccessibility (+ dc:description) | | description | dc:description | | keywords (array or comma string) | dc:subject | | title | dc:title | | creator | dc:creator | | credit | photoshop:Credit | | rights | dc:rights | | copyrightNotice | photoshop:Copyright | | licenseUrl | xmpRights:WebStatement — Google Licensable | | licensor {url, name?} (or flat licensorUrl/licensorName) | IPTC PLUS plus:Licensor — Google "Get this image" link | | digitalSourceType (full IRI or bare term like "trainedAlgorithmicMedia") | Iptc4xmpExt:DigitalSourceType — AI-generated disclosure | | aiGenerated (boolean shorthand) | sets Iptc4xmpExt:DigitalSourceType to trainedAlgorithmicMedia | | ai {prompt?, promptWriter?, system?, systemVersion?} (or flat aiPrompt/aiPromptWriter/aiSystem/aiSystemVersion) | IPTC 2025.1 Iptc4xmpExt:AIPromptInformation / AIPromptWriterName / AISystemUsed / AISystemVersionUsed |

Make images Licensable in Google

The last fields implement what Google Images reads for the Licensable badge:

<Image
  src={barn}
  alt="A weathered red barn at dusk"
  creator="Jane Doe"
  copyrightNotice="© 2026 Example Studio"
  licenseUrl="https://example.com/license/barn"
  licensorUrl="https://example.com/buy/barn"
  width={1200} height={800}
/>

Label AI-generated images (IPTC 2025.1)

For AI-generated assets, embed the IPTC 2025.1 provenance fields plus the Digital Source Type IRI that downstream tools read to label an image as AI-generated:

<Image
  src={market}
  alt="A neon-lit street market at night in the rain"
  aiGenerated
  aiPrompt="neon street market, rain reflections, cinematic 35mm"
  aiPromptWriter="Jane Doe"
  aiSystem="DALL-E via Bing Image Creator"
  aiSystemVersion="3"
  width={1200} height={800}
/>

aiGenerated is shorthand for digitalSourceType="trainedAlgorithmicMedia"; pass digitalSourceType explicitly for other terms (e.g. "compositeSynthetic" — bare CV terms are expanded to the full IPTC IRI). Per IPTC guidance, leave creator off for fully AI-generated images — the prompt writer is explicitly not the creator.

For TypeScript autocomplete on the custom props, augment Astro's image props in src/env.d.ts:

declare namespace Astro {
  interface CustomImageProps {
    description?: string;
    keywords?: string[] | string;
    title?: string;
    aiGenerated?: boolean;
    aiPrompt?: string;
    aiSystem?: string;
  }
}

Supported formats

Whatever you output from Astro: WebP, AVIF, JPEG, PNG (via aeo-image). SVG/GIF and any format aeo-image doesn't handle are passed through untouched — the service degrades gracefully and never fails a build over metadata.

Standards

Metadata is written as Adobe XMP (not legacy IPTC-IIM), conforming to the IPTC Photo Metadata Standard 2025.1 (descriptive + accessibility + rights/licensing + AI-provenance subset) plus Dublin Core, Adobe, and PLUS namespaces — see aeo-image's conformance notes. This includes the 2025.1 AI-generation provenance properties and Iptc4xmpExt:DigitalSourceType (readable by exiftool, named tags from 13.40).

Verifying it worked

Given <Image alt="A weathered red barn under a violet dusk sky in rural Vermont" />, the built file gains embedded metadata:

$ exiftool dist/_astro/barn.abc123.webp | grep -iE "description|alt"
# ── before (default Astro service) ──
#   (no metadata)

# ── after (astro-aeo-image) ──
Description                     : A weathered red barn under a violet dusk sky in rural Vermont
Alt Text Accessibility          : A weathered red barn under a violet dusk sky in rural Vermont

Or check it programmatically:

node -e "import('aeo-image').then(async m=>{const {readFileSync}=await import('node:fs');console.log(m.readMetadata(new Uint8Array(readFileSync(process.argv[1]))))})" dist/_astro/<your-image>.webp
# → { description: '…', altText: '…' }

The pixels are untouched — only a metadata block is added.

Status & scope

• The metadata-embedding core is unit-tested against the published aeo-image.
• On static builds, Astro passes <Image> props (including alt) to the service's transform, which is where embedding happens. For on-demand/SSR image endpoints, the custom props are included in propertiesToHash so they survive into transform; if you rely on SSR image optimization, please smoke-test and open an issue with your Astro version if a prop doesn't come through.
• Wraps astro/assets/services/sharp. If you use a different image service, this won't layer on top of it.

License

MIT