Characters allowed for inserting Alternative text in Acrobat Pro

I am running into this now. I just started adding alt text to pdfs for my organization. There does seem to be a hard limit at which it will no longer let me input text. While I understand the logic given in S. S. 's answer below, it would still be helpful then to see a character count in the input box and actually know the number of characters allowed. 

Hi @santhoshr29800103,

Hope you are doing well. Thanks for writing in!

Answering your question: there is no hard technical character limit for alt text in a PDF, but there are recommended best practices to ensure accessibility and usability, especially for screen reader users.

Here are some references for you:

• PDF/UA Standard (ISO 14289)
  While it does not specify a strict character limit, it emphasizes clear, concise alternative text and recommends using long descriptions if more detail is required.

  • Summary: https://adobe.ly/43B054g

• W3C – Web Accessibility Initiative (WAI)

  • https://adobe.ly/43Zx814

  • It states that alt text should be concise and descriptive. For complex images like charts, a long description (via aria-describedby or a link) is suggested.

• WebAIM Guidelines

  • https://adobe.ly/4kPs3is

  • Recommends keeping alt text short and using linked descriptions for complex content.