Leonardo.ai API Errors: Authorization, Invalid Dimensions and More

How to fix it

Try these in order — the most common fix is first.

1. 1. Authentication

   Copy steps
   1. Send authorization: Bearer <your-key> with a valid UUID key
   2. Invalid response from authorization hook or Authentication hook unauthorized this request means key missing or wrong
   Did this fix it? Yes No

2. 2. Request body

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   1. Use exact names such as sd_version
   2. Send true and false unquoted
   3. Set height and width between 32 and 1024 in multiples of 8
   4. Keep prompts under 1,500 characters
   5. Lower num_images on 400 Too many images
   Did this fix it? Yes No

3. 3. Image IDs and uploads

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   1. Use init_image_id for uploads and init_generation_image_id for Leonardo images
   2. 204 from the presigned upload is success; take the ID from uploadInitImage.id
   3. Remove auth headers from the presigned upload request
   4. For Motion SVD use the image ID from Get a Single Generation, not the generation ID
   Did this fix it? Yes No

4. 4. Webhooks

   1. Key Creation Error Occurred means the callback URL is not https
   Did this fix it? Yes No

Symptoms

The API returns errors such as Invalid response from authorization hook, invalid dimensions, Invalid init image id or couldn't access image.

Why it happens

• API key missing or not sent as authorization: Bearer <key>
• Width or height outside 32-1024 or not a multiple of 8
• Prompt over 1,500 characters (200 for Improve Prompt)
• Parameter names are case-sensitive; booleans sent as strings
• Variation endpoints need a Leonardo-generated image ID, not an upload
• Auth headers sent to the presigned upload URL cause 403
• Webhook URL must be https

This guide also covers

• leonardo ai api error
• leonardo ai invalid response from authorization hook
• leonardo ai api invalid dimensions
• leonardo ai api service error

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