DNS RECORD for CNAME is limited

What I’m trying to do here is creating CNAME record for DCV purposes. Previously, we were able to add target value with 98 characters, now I’m trying to change to a new value with 97 character and it didn’t let me to do so with an error “The maximum target label length is 63 characters” and it gets more weird when I able to save by changing some character inside the previous target but unable to save a whole new value for new target. Could someone tell me why is this happen?

A DNS label has always been limited to 63 octets, and the complete name is limited to 255 octets.

Are you sure you are being asked to create a CNAME?

Can you share a screenshot of the instructions your CA is providing. (Redact your own domain name)

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Here is the link: https://support.comodoca.com/articles/Knowledge/Domain-Control-Validation-DCV-Methods
It requiring me to create the CNAME record right?

Based on the screenshot that looks like a bug… if you can open a ticket you should … else maybe someone will escalate it.

note that a hex (base-16) encoded SHA-256 hash will not fit in a single DNS label because it is too long.
The SHA-256 hash should therefore be split into two labels, each 32 characters long.

In all the examples they give there is a period in the middle of the SHA-256 hash.

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Yup, after I put a period next to the 32nd character, then I’m able to save the record. Thanks mate.


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