INFRA Signal 124
DNS name maximum readable length is 253 characters due to wire encoding overhead
↗
The 255-octet DNS name limit translates to 253 readable ASCII characters because length bytes and the root label terminator consume two of those octets in wire encoding.
Engineers validating or constructing DNS names programmatically may encounter rejections for strings that appear to be under the 255-character limit. Understanding that the limit applies to the wire encoding, not the readable string, prevents debugging confusion and ensures correct validation logic.
Written by elseif from the cluster below · every claim links back to a sourceThe three things worth knowing
The DNS name length limit of 255 applies to octets in wire encoding, not readable characters.
Length bytes for each label and the zero-byte root label terminator consume octets, reducing the readable ASCII limit to 253 characters.
UTF-8 encoding further reduces the readable character limit since multi-byte characters consume more octets per character.
THE CLUSTER