AI Alt Text Generator: Bulk Alt Text for Image URL Lists

Generate accessibility- and SEO-ready alt text for images at scale using AI vision. Feed it a list of image URLs, like product catalog exports, CMS asset libraries, or migration lists, and get alt text back for each, ready to export to CSV, JSON, or Excel.

Great for: image alt text, bulk alt text generation, AI image captioning, WCAG / accessibility compliance, SEO images, e-commerce product catalogs, and CMS migrations.

Need a whole-site audit instead? If you want to scan an entire website (sitemap crawling, not just a single page) and optionally generate AI descriptions for what it finds, use the companion Image Alt Text Checker. It has the same AI description add-on plus full-site crawling and a no-AI metadata audit mode.

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What it does

• Give it a list of image URLs → get alt text for each. This is the primary way to use this actor.
• Or check a single page: point it at one page and it finds <img> tags missing alt text and writes it for you. (For crawling a whole site, use the Image Alt Text Checker instead.)
• Multilingual output, a length cap tuned for WCAG (~125 characters), an optional SEO keyword hint, and decorative-image detection (recommends empty alt="" for purely ornamental images instead of a bogus description).

Output

One dataset row per image, with a table view built in:

Field	Description
imageUrl	The image that was described
altText	The generated alt text (empty for decorative images)
flaggedDecorative	true if the image was judged purely decorative
charCount	Length of the alt text
pageUrl	The page it was found on (single-page check only)
existingAlt	The alt text already present, if any
status	ok, error, or mocked

A run summary (counts + estimated cost) is stored in the key-value store under SUMMARY.

Example input

A list of image URLs, Spanish, with an SEO hint:

{
  "imageUrls": [
    "https://example.com/products/mug-01.jpg",
    "https://example.com/products/mug-02.jpg"
  ],
  "language": "Spanish",
  "keywordHint": "handmade ceramic mug, product page",
  "style": "descriptive"
}

Single-page check (only images missing alt):

{
  "startUrls": [{ "url": "https://example.com" }],
  "onlyMissingAlt": true,
  "language": "English",
  "style": "concise",
  "maxLength": 125,
  "maxImages": 200
}

Key options

Option	Default	Notes
imageUrls	[]	Primary use: direct image URLs
startUrls	[]	Single-page check (not a full-site crawl; see Image Alt Text Checker for that)
onlyMissingAlt	true	Single-page check: skip images that already have alt text
language	English	Any language
style	concise	concise (WCAG-friendly) or descriptive
maxLength	125	Hard character cap
keywordHint	None	Woven in naturally; no keyword stuffing
detectDecorative	true	Recommends alt="" for ornamental images
maxImages	200	Per-run safety cap (controls cost)
model	google/gemini-2.5-flash-lite	Any OpenRouter vision model (e.g. openai/gpt-5-nano, amazon/nova-lite-v1)
apiBaseUrl	OpenRouter	OpenAI-compatible base URL: swap for OpenAI/Groq/Together/local
maxPagesPerCrawl	1	Pages to crawl per start URL (same domain)
concurrency	5	Parallel image requests

Pricing

Billed per image processed (pay-per-event). Failed images are not charged. On cheap OpenRouter vision models the underlying cost is roughly $0.0001–0.0003 per image. Supported image formats: JPEG, PNG, GIF, WebP (SVG/ICO are skipped).

Please note (fair use & accuracy)

• Only scan websites you own or have permission to analyze. You supply the target; you're responsible for it.
• Alt text is AI-generated: review it before publishing, especially in legally-sensitive or compliance-critical contexts.
• Images are processed transiently and are not stored beyond the run; your results live in your dataset.

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Running / self-hosting

The hosted actor provides the AI backend: you just pay per image. To self-host or run locally:

1. npm install
2. Set OPENROUTER_API_KEY (env var) or pass openrouterApiKey in the input. Get a key at https://openrouter.ai/keys
3. npx apify-cli run (or npm start). Without a key it runs in mock mode (placeholder alt text) so you can test the pipeline.

To use a different provider, set the apiBaseUrl input to any OpenAI-compatible endpoint (OpenAI, Groq, Together, a local server) and supply that provider's key.

Configure monetization (maintainer)

On the Apify platform, set OPENROUTER_API_KEY as an Actor environment secret, and configure a pay-per-event price for the event image-processed in the Actor's monetization settings. The code calls Actor.charge({ eventName: 'image-processed' }) once per successfully processed image.

Built with Apify SDK + Crawlee + OpenRouter vision models.