217 subdomain names reach the 253-character DNS limit
A look inside the fixed GetDomainLists release of 16 October 2026: 306,042,862 registrable domains and 1,235,195,702 subdomains, published as two plain-text files. Names only — historically observed names and their registrable roots, not evidence that any name currently resolves or hosts content.
- Longest subdomain name
- 253 characters
- Deepest subdomain
- 120 labels
- Longest registrable domain
- 91 characters
- Name part of 7–15 characters
- 62.7%
the DNS maximum; 217 names reach it
below its registrable domain
4 names this long
of registrable domains
How long can a domain name get, and how many labels can sit in front of it? DNS sets hard limits. In this release most names stay far from them, but some reach them exactly: 217 subdomain names are as long as DNS allows.
The limits DNS sets
In the ASCII form used in these files, a complete name without a trailing root dot can have up to 253 characters, and each label — a part between dots, such as www — up to 63 characters. For internationalized names, count the encoded xn-- form, not the decoded display text. There is no separate limit on depth: it is bounded by the length limit, because every label takes at least one character plus its dot.
How long registrable domains are
The name part is the label you register, without the ending: example in example.co.uk.
| Name part length (characters) | Share of registrable domains |
|---|---|
| 1–3 | 0.7% |
| 4–6 | 14.4% |
| 7–10 | 30.7% |
| 11–15 | 32.0% |
| 16–20 | 15.2% |
| 21 or more | 7.1% |
Counting the whole name with its ending, a registrable domain in this release averages 16.1 characters. The longest is 91 characters (4 names). 9,163 registrable domains use a 63-character label, the most a single label may hold.
How long subdomain names are
| Full name length (characters) | Subdomain names | Share |
|---|---|---|
| Up to 20 | 224,333,838 | 18.2% |
| 21–40 | 403,889,500 | 32.7% |
| 41–63 | 311,444,611 | 25.2% |
| 64–100 | 288,143,710 | 23.3% |
| 101–200 | 7,378,638 | 0.6% |
| 201–252 | 5,188 | under 0.1% |
| 253, the maximum | 217 | under 0.1% |
A subdomain name averages 43.6 characters. 217 names are exactly 253 characters long, the most DNS allows, and 1,188,528 subdomain names contain a 63-character label.
How deep subdomains go
Depth counts the labels to the left of the registrable domain (a.example.co.uk is depth 1, a.b.example.co.uk is depth 2).
| Depth | Share of subdomains |
|---|---|
| 1 | 42.1% |
| 2 | 17.0% |
| 3 | 14.7% |
| 4 | 4.4% |
| 5 | 6.8% |
| 6 or more | 15.0% |
57.9% of subdomain names are two or more levels deep; the average is 2.7. The deepest name has 120 labels in front of its registrable domain, shaped like a.b.c.…example.com. This page describes the shape of names at the limits and does not print the names themselves.
What this data cannot tell you
- Whether a name is live, resolves in DNS, or serves a website today.
- Who created a long or deep name, or why.
- Everything on the internet. Coverage is incomplete; these are counts in this release.
Try it yourself
Try the format first with the free 1,000-name samples. Both full files are $9 once, with 30 days to download.
Counts for every ending are on the TLD list with a free CSV; how subdomains are spread across domains is in the concentration analysis.