What is a TXT record? Verification codes, SPF and DKIM in one type

Each TXT record is made of one or more strings, and each string can be at most 255 bytes long. That limit goes back to the original DNS spec (RFC 1035), where every string starts with a single length byte. Longer values, like a 2048-bit DKIM key, get split into several strings inside the same record. SPF and DKIM readers join those strings back together with nothing in between, so a split in the middle of a key does no harm.

Where a record sits matters as much as what it says. SPF lives on the domain itself. DMARC lives at _dmarc.example.com. DKIM keys live under _domainkey, at a name like google._domainkey.example.com. Verification codes from search engines, email providers and SaaS tools usually go on the domain itself, which is why a busy domain can carry a dozen TXT records at once.

The DNS Lookup lists every TXT record at a name with its TTL. It joins split strings so long keys read as one value, and it pulls the SPF and DMARC records out of the list and explains them.