TXT record
A free-text DNS record originally designed for human-readable notes. Now used heavily for ownership verification (Google, AWS, Cloudflare) and email auth (SPF, DKIM, DMARC).
What goes in one
Anything that fits in a string. Common uses: ‘v=spf1 include:_spf.google.com ~all’ for SPF, an ‘_acme-challenge’ subdomain TXT for Let’s Encrypt DNS-01, and platform-specific verification tokens.
Limit
A single TXT record string is capped at 255 characters but can be split across multiple strings.