Alt Text Batch Generator

Batch-process multiple images to generate AI-powered alt text descriptions for web accessibility using Qwen2.5-VL vision model.

	Free plan (preview)	Paid Apify plan (Starter and up)
Images described per run	1 (the first URL)	every URL you enter (up to 500 a run)
The other images	counted in a free-plan-preview row: how many were queued, and an estimate (BRONZE price) of a paid run of the same input	described
Price	same events	same events, with plan discounts: BRONZE 20% off, SILVER 35% off, GOLD and up 48% off

A free run ends as SUCCEEDED with a status message that says how many images were left out. Run the same input again on a paid plan for all of them.

Overview

This Actor processes up to 500 images in a single run and generates alt text descriptions suitable for screen readers and accessibility compliance. Each successfully processed image is charged at $0.01 (pay-per-event pricing).

Key Features

• Batch Processing: Process up to 500 images per run
• AI-Powered: Uses Qwen2.5-VL vision model via ntriq AI service
• Flexible Output: Choose between concise (WCAG-compliant max 125 chars) or detailed (2-3 sentence) descriptions
• Multi-Language: Supports 10 languages (English, Korean, Japanese, Chinese, Spanish, French, German, Italian, Portuguese, Russian)
• Pay-Per-Event: $0.01 per generated alt text; $0.002 for an image URL whose host refuses it (see Pricing)
• Error Resilience: Continues processing even if individual images fail
• Detailed Logging: Track processing time and confidence scores per image

Input

Provide an array of publicly accessible image URLs:

{
  "urls": [
    "https://example.com/image1.jpg",
    "https://example.com/image2.png",
    "https://example.com/image3.webp"
  ],
  "language": "en",
  "style": "concise",
  "maxUrls": 500
}

Input Parameters

Parameter	Type	Default	Required	Description
urls	array	—	✓	Array of image URLs (1-500 items)
language	string	en	—	Language code: en, ko, ja, zh, es, fr, de, it, pt, ru
style	string	concise	—	Output style: concise (≤125 chars) or detailed (2-3 sentences)
maxUrls	integer	500	—	Safety limit on processing count (1-500)

Output

Each image produces one dataset record:

{
  "url": "https://example.com/image1.jpg",
  "status": "success",
  "altText": "A fluffy orange tabby cat sitting on a wooden windowsill",
  "detailedDescription": null,
  "language": "en",
  "model": "Qwen2.5-VL",
  "processingTimeMs": 2450,
  "confidence": 0.85,
  "error": null,
  "code": null
}

Output Fields

Field	Type	Description
url	string	Original image URL
status	string	success or error
altText	string	Generated alt text (concise style)
detailedDescription	string|null	Detailed description (detailed style only)
language	string	Output language code
model	string	AI model name (Qwen2.5-VL)
processingTimeMs	integer	Processing time in milliseconds
confidence	number	AI confidence score (0-1)
error	string|null	Error message if failed
code	string|null	Error code: INVALID_URL, TIMEOUT, API_ERROR, etc.

Usage Examples

Example 1: Basic Batch Processing (English, Concise)

{
  "urls": [
    "https://picsum.photos/id/237/400/300.jpg",
    "https://upload.wikimedia.org/wikipedia/commons/1/18/Dog_Breeds.jpg"
  ],
  "language": "en",
  "style": "concise"
}

Cost: $0.02 (2 images × $0.01)

Example 2: Large Batch with Detailed Descriptions (Korean)

{
  "urls": [
    "https://example.com/image1.jpg",
    "https://example.com/image2.jpg",
    "https://example.com/image3.jpg",
    "...up to 500 images..."
  ],
  "language": "ko",
  "style": "detailed",
  "maxUrls": 500
}

Cost: $0.03 - $5.00 depending on successes (1-500 images × $0.01)

Pricing

Event	Price (FREE tier list price)	When it is charged
alt-text-generated	$0.01	once per image whose alt text row is delivered
image-checked	$0.002	once per image URL that our service tried to download and the Actor then checked itself, and whose host answered with an HTTP error, a non-image or an empty body (code: "IMAGE_UNREACHABLE", errorSide: "target", reason, httpStatus). Charged only once this event is on the live price list

Who is behind a failed URL. When the URL's own host answers 401, 403, 404 or 410, the check is done and the answer is the host's: errorSide: "target" with reason (login-required, forbidden, not-found, gone) and httpStatus, charged as image-checked. When it answers 429, 503 or another temporary code, the Actor waits briefly and asks once more; the same kind of answer again is the host's own state: reason: "temporarily-unavailable" with the HTTP code, charged the same way. Our side is never charged: our time limit, a host that never answered, our vision service's errors (errorSide: "service").

If the platform restarts a run, the new run life reads the run's own dataset and the platform's charge counts: inputs already answered are not processed, delivered or charged again. If the dataset cannot be read back, the run stops without processing or charging anything more.

Not charged: TIMEOUT, API_ERROR, PROCESSING_ERROR, EXCEPTION rows (errorSide: "service" — our side), INVALID_URL/INVALID_INPUT rows (rejected before any work), notice rows. Plan discounts: BRONZE 20%, SILVER 35%, GOLD and up 48%.

The run stops when its maximum charge is reached: no further image is sent to the vision service, a charge-limit-reached notice row says how many images were not processed, and the run ends as SUCCEEDED. If our vision service fails 3 images in a row, the run stops with a free service-unavailable notice row instead of spending your run time on the rest.

Cost Examples

Images	Success	Cost
10	10	$0.10
50	48 (2 failed)	$0.48
100	95 (5 failed)	$0.95
500	500	$5.00

Timeout & Rate Limiting

• Per-image timeout: 180 seconds, and never longer than the time the run has left
• Batch timeout: the run timeout you set in Run options (default 1 hour). Images take about 5 seconds each, so 500 images need about 40 minutes — set a longer run timeout for big batches
• Near the run timeout: the run stops starting new images, keeps every result already delivered, and adds one free time-budget-reached notice row listing how many inputs were not processed — re-run with the remaining URLs
• Rate limit: 100ms delay between requests (built-in throttling)

Error Codes

Code	Meaning	Recovery
INVALID_INPUT	Missing/invalid URL parameter	Check URL format
INVALID_URL	URL not HTTP(S) or malformed	Verify URL is valid and public
TIMEOUT	Request exceeded the per-image limit (up to 180 seconds)	Image too large or service overloaded
IMAGE_UNREACHABLE	The image host answered with an error (401/403/404/410, or 429/503 twice — reason and httpStatus say which), not an image, or empty	Check that the URL opens publicly
API_ERROR	AI service returned error	Check service status
PROCESSING_ERROR	Other processing failure	Check image format/size
EXCEPTION	Unhandled exception	Contact support

Legal Notice

Image Source Responsibility

• You must only submit images that you own or have explicit permission to analyze.
• You are responsible for complying with the source website's Terms of Service and robots.txt.
• Do not use this tool to analyze images from stock photo sites (Getty, Shutterstock) without a valid license.

Copyright

• Generated alt text descriptions are not derivative works of the original images.
• However, fetching images from third-party URLs may violate the source site's Terms of Service.
• We assume no liability for third-party intellectual property claims arising from your use.

WCAG Compliance

• AI-generated alt text is a starting point, NOT a guarantee of WCAG 2.1 or ADA compliance.
• All generated descriptions must be reviewed by a human before production use.
• This tool assists accessibility efforts but does not replace professional accessibility auditing.

AI Limitations

• Descriptions may contain inaccuracies or miss important context.
• Specialized images (medical, technical, charts) require professional review.

Data Processing

• Images are fetched temporarily for analysis and immediately discarded.
• No images are stored, cached, or redistributed by our service.

Technical Details

AI Service Integration

• Endpoint: hosted vision model backend (Qwen2.5-VL)
• Request Timeout: up to 180 seconds per image
• Supported Formats: JPEG, PNG, WebP, GIF, BMP
• Max Image Size: Depends on AI service (typically 100MB)

Environment Variables (Optional)

$AI_REQUEST_TIMEOUT=180000

Processing Pipeline

1. Validate input array and language/style parameters
2. For each URL:
   • Validate URL format
   • Call AI service with optimized prompt
   • Collect response (alt text or error)
   • Push to dataset
   • Charge on success (or image-checked when the host refused the URL); stop at the run's maximum charge
3. Log summary (success/error counts, total cost)

Limitations

Limitation	Value
Max images per run	500 on paid plans, 1 on the free plan
Timeout per image	180 seconds (shorter when the run is nearly out of time)
Total batch timeout	Your run timeout (Apify default 1 hour)
Concurrent requests	Sequential (100ms between)
Supported formats	JPEG, PNG, WebP, GIF, BMP

Support

For issues or questions:

1. Check error codes and logs in run output
2. Verify all image URLs are publicly accessible
3. Confirm language code is supported
4. Review AI service status

Version History

• v1.0.0 (2026-03-30): Initial release
  • Batch processing (up to 500 images)
  • Concise and detailed styles
  • Multi-language support
  • Pay-per-event billing

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Last Updated: 2026-03-30 Maintainer: ntriq Engineering License: Apache 2.0

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