Can I claim my 23 year old child who lived with us and was supported 100% by us for entire year. He did not work due to a disability.

You can claim him as dependent as long as he meets the following requirements:

Qualifying child:

• They're related to you.
• They aren't claimed as a dependent by someone else.
• They're a US citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t filing a joint return with their spouse.
• They're under the age of 19 (or 24 for full-time students).
• There's no age limit for permanently and totally disabled children.
• They lived with you for more than half the year (exceptions apply).
• They didn't provide more than half of their own support for the year.

Or, Qualifying relative:

• They don't have to be related to you (despite the name).
• They aren't claimed as a dependent by someone else.
• They're a US citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t filing a joint return with their spouse.
• They lived with you the entire year (exceptions apply).
• They made less than $5,050 in 2024.
• You provided more than half of their financial support.

So, if he is 23, but has been living with us and supported by us we can't claim him because he is over 19?

Correct.  If he is not a student or totally and permanently disabled, UNLESS his income is less than $5.050 you cannot claim him even if you are fully supporting him.

If his income is less than $5,050 you can claim him even if he is not a student or disabled.