API Documentation

Overview

AltText API provides a simple REST API for generating high-quality alt text for images using advanced AI vision models.

Key Features

• 2-3 second response times
• WCAG 2.1 AA compliant output
• 32+ languages supported
• Batch processing (up to 50 images)
• 99.9% uptime guarantee
• Privacy-first (images not stored)

Base URL

https://alttextapi.com

Pricing

• $0.03 per image (3 cents)
• No monthly fees or subscriptions
• Pay only for successful generations
• Minimum purchase: $5 (166 images)

WCAG 2.1 Compliance

AltText API generates alt text that helps you meet WCAG 2.1 Level AA Success Criterion 1.1.1 (Non-text Content), which requires meaningful alternative text for images.

What We Provide

• Contextual Descriptions: Our AI analyzes images to provide meaningful, descriptive alt text
• Concise Format: Alt text is kept under 125 characters when possible for optimal screen reader experience
• Multi-Language Support: Generate alt text in 32+ languages for international accessibility
• Consistent Quality: Advanced vision models (Qwen 2.5 VL, Gemini 2.5) ensure reliable output

Your Responsibility

• Review Generated Content: AI is a tool to assist, not replace, human judgment
• Context Matters: Ensure alt text fits the surrounding content and purpose
• Decorative Images: Use empty alt="" for purely decorative images (API doesn't make this decision)
• Complex Images: Charts, diagrams, and infographics may need longer descriptions beyond alt text
• Final Compliance: You are responsible for ensuring your implementation meets accessibility standards

Quick Start

1. Create Account

Sign up at alttextapi.com to get your API key.

2. Get API Key

After signing up, find your API key in the dashboard.

3. Make Your First Request

curl -X POST https://alttextapi.com/api/generate \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "image_url": "https://example.com/image.jpg",
    "language": "en"
  }'

4. Get Response

{
  "alt_text": "A golden retriever playing fetch in a park",
  "language": "en",
  "cost": "$0.03",
  "balance": "$9.97",
  "images_remaining": 332
}

Authentication

All API requests must include your API key in the Authorization header using the Bearer scheme:

Authorization: Bearer YOUR_API_KEY

API Key Format: Keys start with ak_ followed by 48 hexadecimal characters (e.g., ak_a1b2c3d4...)

Getting Your API Key

1. Sign up at alttextapi.com
2. Log in to your dashboard
3. Copy your API key
4. Store it securely (use environment variables)

API Endpoints

{
  "alt_text": "A golden retriever playing fetch in a park",
  "language": "en",
  "cost": "$0.03",
  "balance": "$9.97",
  "images_remaining": 332
}

{
  "images": [
    {"image_url": "https://example.com/image1.jpg"},
    {"image_url": "https://example.com/image2.jpg"},
    {"image_base64": "iVBORw0KGgoAAAA..."}
  ],
  "language": "en"
}

{
  "results": [
    {
      "success": true,
      "alt_text": "A golden retriever playing fetch"
    },
    {
      "success": true,
      "alt_text": "A sunset over the ocean"
    },
    {
      "success": false,
      "error": "Invalid image URL"
    }
  ],
  "total": 3,
  "successful": 2,
  "failed": 1,
  "cost": "$0.06",
  "balance": "$9.91",
  "images_remaining": 330
}

{
  "email": "user@example.com",
  "balance": "$9.97",
  "total_spent": "$0.03",
  "images_remaining": 332
}

{
  "message": "Account created successfully",
  "api_key": "sk_live_abc123...",
  "email": "user@example.com"
}

{
  "email": "user@example.com",
  "api_keys": [
    {
      "key": "sk_live_abc123...",
      "name": "Default",
      "created_at": "2025-09-30T12:00:00Z"
    }
  ]
}

Code Examples

cURL

curl -X POST https://alttextapi.com/api/generate \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "image_url": "https://example.com/image.jpg",
    "language": "en"
  }'

JavaScript (Node.js)

const response = await fetch('https://alttextapi.com/api/generate', {
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${process.env.ALTTEXT_API_KEY}`,
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    image_url: 'https://example.com/image.jpg',
    language: 'en'
  })
});

const data = await response.json();
console.log(data.alt_text);

Python

import requests
import os

response = requests.post(
    'https://alttextapi.com/api/generate',
    headers={
        'Authorization': f'Bearer {os.getenv("ALTTEXT_API_KEY")}',
        'Content-Type': 'application/json'
    },
    json={
        'image_url': 'https://example.com/image.jpg',
        'language': 'en'
    }
)

data = response.json()
print(data['alt_text'])

PHP

$ch = curl_init('https://alttextapi.com/api/generate');

curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    'Authorization: Bearer ' . getenv('ALTTEXT_API_KEY'),
    'Content-Type: application/json'
]);
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode([
    'image_url' => 'https://example.com/image.jpg',
    'language' => 'en'
]));

$response = curl_exec($ch);
$data = json_decode($response, true);

echo $data['alt_text'];

Ruby

require 'net/http'
require 'json'

uri = URI('https://alttextapi.com/api/generate')
request = Net::HTTP::Post.new(uri)
request['Authorization'] = "Bearer #{ENV['ALTTEXT_API_KEY']}"
request['Content-Type'] = 'application/json'
request.body = {
  image_url: 'https://example.com/image.jpg',
  language: 'en'
}.to_json

response = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) do |http|
  http.request(request)
end

data = JSON.parse(response.body)
puts data['alt_text']

Error Handling

HTTP Status Codes

Error Response Format

{
  "error": "Insufficient credits. Please add more credits to continue."
}

Common Errors

Insufficient Credits

{
  "error": "Insufficient credits"
}

Solution: Add credits at /dashboard

Invalid API Key

{
  "error": "Invalid API key"
}

Solution: Check your API key in the dashboard

Invalid Image URL

{
  "error": "Invalid or inaccessible image URL"
}

Solution: Ensure the image URL is publicly accessible

Rate Limits

AltText API has generous rate limits to support production applications:

• No hard rate limits on paid accounts
• Automatic fallback between AI providers ensures reliability
• Cloudflare Workers can handle millions of requests
• 99.9% uptime guarantee

Best Practices

• Use batch processing for multiple images
• Implement retry logic with exponential backoff
• Cache generated alt text to avoid duplicate requests
• Monitor your balance to avoid service interruption

Integrations

WordPress

Official WordPress plugin available for automatic alt text generation.

Features

• Auto-generate alt text on image upload
• Bulk process existing images
• WooCommerce support
• Multi-language support

Installation

1. Download the plugin from our GitHub
2. Upload to WordPress → Plugins → Add New
3. Activate and enter your API key
4. Enable auto-generate in Settings → AltText API

Shopify (Coming Soon)

Shopify app integration is in development. Join our waitlist in the dashboard.

Custom Integration

Use our REST API to integrate with any platform:

• Content Management Systems (Drupal, Joomla, etc.)
• E-commerce platforms (Magento, BigCommerce, etc.)
• Custom applications
• Automation tools (Zapier, Make, etc.)

Support

Resources

• Dashboard: /dashboard
• GitHub: github.com/nijaru/alttextapi
• Privacy Policy: /privacy
• Terms of Service: /terms

Common Questions

Do you store my images?

No. Images are processed in-memory only and immediately discarded. We never store your images.

Is the alt text WCAG compliant?

Yes. All generated alt text meets WCAG 2.1 Level AA standards. However, we recommend human review for critical applications.

What languages are supported?

32+ languages including English, Spanish, French, German, Chinese, Japanese, and more.

Can I get a refund?

Credits are non-refundable once purchased, but they never expire.

Need Help?

For technical support or questions, check our GitHub repository or contact us through the dashboard.