The DNS standard limits each label (the part between dots, like 'example') to 63 characters, and the whole domain name to 255 octets — about 253 usable characters. The piece you register before the TLD is therefore capped at 63 characters. Allowed characters are letters, digits and hyphens (not at a label's start or end); other scripts use Punycode-encoded IDNs. Minimums and premium thresholds vary by registry, but the maximum is the same everywhere — it is set by the protocol, not the TLD.
The two limits that matter
Domain length is governed by the DNS protocol, defined in the foundational DNS RFCs (RFC 1034 and RFC 1035). Two numbers do almost all the work. First, each label — every dot-separated segment — may be at most 63 octets. Second, the full domain name may be at most 255 octets, which works out to roughly 253 usable characters once the length bytes and trailing dot are accounted for. Because the second-level label (the name you register, before the TLD) is itself a single label, it is capped at 63 characters — and that is the limit nearly everyone actually encounters. These are protocol limits, so they apply identically across generic and country-code extensions alike.
Domain length and character rules
The protocol-level limits that apply to every TLD, plus what varies by registry.
| Rule | Limit / value | Set by | Notes |
|---|---|---|---|
| Per-label maximum | 63 octets | DNS protocol (RFC 1035) | Applies to the name you register; universal across all TLDs. |
| Full-name maximum | 255 octets (~253 chars) | DNS protocol | Total across all labels including dots. |
| Minimum length | 1 character (protocol) | Registry policy | Short names often reserved/premium; varies by TLD. |
| Allowed characters | A–Z, 0–9, hyphen | DNS protocol (LDH rule) | Case-insensitive; hyphen not at start or end. |
| Non-ASCII (IDN) | via Punycode (xn--) | IDNA standard | Encoded form still must fit 63-char label limit. |
| Premium short names | 1–3 chars often | Registry policy | May be reserved, auctioned or surcharged per TLD. |
Protocol limits are defined in the DNS standards (RFC 1034/1035) and IDNA; registry-specific minimums and premium thresholds are set per TLD. See the IANA root zone database and individual registry policies.
What this means when you register
For almost every project the practical rule is simple: keep the registrable part to 63 characters or fewer — and in reality far fewer, because short, memorable names perform better. The full 253-character ceiling only becomes relevant with deep subdomain chains, which most sites never approach. If you want a non-Latin name (Arabic, Chinese, Cyrillic and so on), the internationalised domain name is converted to a Punycode xn-- form behind the scenes, and that encoded form is what must fit the 63-character limit — so a long non-ASCII name can hit the cap sooner than its visible length suggests. Registry minimums and premium tiers for very short names vary by extension, so if you are after a one- or two-character name, check that specific TLD's policy.