ASCII Domain Names: What the Term Means

ASCII domain names are internet addresses written only with the basic Latin alphabet, digits, and hyphens—the characters standardized by the American Standard Code for Information Interchange (ASCII). When you type a domain like example.com or my-site.org, you are using an ASCII domain name. The term exists to distinguish these traditional addresses from internationalized domain names (IDNs), which contain non-ASCII characters such as accented letters, Cyrillic, Chinese, or Arabic script.

Formula

The calculator works out your average pace and speed for a run or ride. You enter the finish time in minutes and the distance in kilometers. The formulas are:

Pace (min/km) = Finish time (min) ÷ Distance (km)

Speed (km/h) = Distance (km) ÷ (Finish time (min) ÷ 60)

Variables:
• t = finish time in minutes (min)
• d = distance in kilometers (km)
• pace = minutes per kilometer (min/km)
• speed = kilometers per hour (km/h)

Worked Example

Using the default values: finish time = 50 minutes, distance = 10 km.

Step 1: Calculate pace: 50 ÷ 10 = 5.00 min/km.

Step 2: Calculate speed: 10 ÷ (50 ÷ 60) = 10 ÷ 0.8333 = 12.00 km/h.

So with a 50-minute 10 km run, your average pace is 5:00 per kilometer and your average speed is 12.0 km/h.

Why ASCII Matters for Domain Names

The Domain Name System (DNS) was designed in the 1980s, when the internet was primarily English-language and US-centric. The original specifications only allowed letters A–Z, digits 0–9, and hyphens. This restriction ensured that every domain could be typed on any keyboard and transmitted reliably through early networking protocols that often assumed ASCII. Even today, the core DNS infrastructure technically works with ASCII only; non-ASCII domains are converted into a special ASCII form called punycode before they are processed.

For example, the Chinese domain 例�.公� is converted to xn--fsqu00a.xn--55qx5d in punycode. The xn-- prefix signals that the label is an internationalized domain name encoded in ASCII. This allows the DNS to handle non-Latin scripts without changing the underlying protocol.

How ASCII Domains Work

Every domain name consists of labels separated by dots. Each label can be up to 63 characters, and the full domain name (including dots) can be up to 253 characters. The allowed characters are:

• Letters A–Z (case-insensitive, so EXAMPLE.com and example.com are the same)
• Digits 0–9
• Hyphens (-), but never at the beginning or end of a label

No other symbols, spaces, or underscores are permitted. This restriction is part of the DNS standard (RFC 1035) and applies to all domain names at the technical level, even IDNs after punycode conversion.

When you register an ASCII domain, you are essentially reserving a unique string that maps to an IP address through DNS records. The registries (like Verisign for .com) enforce the character rules, and the DNS servers handle the rest.

ASCII vs. Internationalized Domain Names (IDNs)

IDNs were introduced in the early 2000s to allow non-ASCII characters in domain names. They are encoded using punycode, a special ASCII representation that starts with xn--. For instance, the German domain bücher.de becomes xn--bcher-kva.de.

The key difference is user-facing: an ASCII domain is what you see in the address bar when typing traditional characters, while an IDN displays in its native script. However, both are stored and transmitted as ASCII punycode behind the scenes. This means that an ASCII domain and an IDN are technically distinct—bücher.de and bucher.de are different domains, which can lead to confusion or phishing attempts if a user mistakes one for the other.

Common Problems and Misconceptions

One common misconception is that ASCII domains are “English-onlyâ€� or that they cannot contain accented characters. In fact, ASCII domains are simply restricted to the basic Latin alphabet; you can use them for any language that uses those characters. For example, a Spanish domain like mañana.com is not ASCII because of the ñ, but manana.com is.

Another issue is homograph attacks. Because many scripts share visually similar characters (e.g., the Latin letter “aâ€� and the Cyrillic “аâ€�), an attacker could register an IDN that looks like a legitimate ASCII domain. This is why browsers display punycode for IDNs in many cases, showing xn-- in the address bar to alert users.

Also, some people assume that hyphens are allowed anywhere, but they are prohibited at the start or end of a label. Double hyphens are also restricted in some positions (e.g., the third and fourth positions of a label are reserved for punycode, so ab--cd.com is not allowed).

How to Choose an ASCII Domain

When picking an ASCII domain, consider the following:

• Keep it short and memorable—shorter names are easier to type and less prone to typos.
• Avoid hyphens if possible; they are often forgotten or mistyped, and they can look unprofessional.
• Use keywords that describe your site’s purpose, but avoid trademarked terms.
• Check for similar names that could cause confusion, especially IDNs that look like your domain.
• Choose the right extension (.com, .org, .net, etc.) based on your target audience and purpose.

You can check availability through any domain registrar. If your preferred name is taken, consider a different extension or a slight variation, but be cautious of typosquatting—registering a common misspelling of a popular site is often frowned upon and can lead to legal issues.

Costs and Registration

ASCII domain registration costs vary by extension and registrar. Typically, .com domains cost around $10–$15 per year, while some newer extensions like .xyz or .online may be cheaper. Prices are set by the registry and the registrar, so they can change. There are no additional costs for using ASCII characters, but IDNs sometimes carry a premium because they are newer and less common.

When you register a domain, you are essentially leasing it for a year (or more). You must renew it annually to keep it. If you let it expire, it becomes available to others after a grace period.

Safety and Security Considerations

ASCII domains are generally safe, but you should be aware of phishing risks. Attackers often register look-alike domains using IDNs or subtle character substitutions. For example, paypa1.com (with a digit “1â€� instead of “lâ€�) is an ASCII domain that mimics PayPal. Always check the URL carefully before entering credentials.

To protect yourself, use a reputable registrar with two-factor authentication, enable domain locking to prevent unauthorized transfers, and consider privacy protection to hide your contact information from public WHOIS records. Also, be wary of emails claiming your domain is expiring—verify directly with your registrar.

Alternatives to ASCII Domains

If you need a non-ASCII domain, IDNs are the only official alternative. They allow you to register domains in scripts like Arabic, Chinese, Cyrillic, or Devanagari. However, IDNs have drawbacks: they can be harder to type on standard keyboards, they may not be supported by all email clients, and they are more susceptible to phishing due to homograph attacks.

Another alternative is to use a subdomain or a URL shortener that points to your site, but these do not replace a domain name. For most users, an ASCII domain remains the simplest and most reliable choice.

Frequently Asked Questions

What is the difference between an ASCII domain and a regular domain?

There is no difference—every domain name you type in a browser is technically ASCII. The term “ASCII domain� is used to distinguish traditional domains from internationalized ones that use non-Latin scripts. All domains are converted to ASCII punycode for DNS resolution.

Can I use numbers in an ASCII domain?

Yes, digits 0–9 are allowed anywhere in a label, except as the entire TLD (top-level domain). For example, 123.com is valid, but .123 is not a valid TLD. Hyphens are also allowed, but not at the start or end.

Why do some domains start with xn--?

The xn-- prefix indicates that the label is an internationalized domain name encoded in punycode. For instance, xn--bcher-kva.de is the ASCII representation of bücher.de. This encoding allows non-ASCII characters to be handled by the DNS.

Are ASCII domains case-sensitive?

No, domain names are case-insensitive. Example.com and example.com are the same. However, the path after the domain (e.g., /Page) can be case-sensitive on the web server.

Can I register an ASCII domain with a hyphen?

Yes, hyphens are allowed, but they cannot be the first or last character of a label. For example, my-site.com is valid, but -mysite.com and mysite-.com are not. Avoid hyphens if possible, as they are often mistyped.

What happens if I type a non-ASCII domain in a browser?

Modern browsers automatically convert non-ASCII domains to punycode and display the punycode version in the address bar (e.g., xn--bcher-kva.de). This is a security measure to prevent homograph attacks. The user still sees the native script in the page content.

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in t | Finish time | min | 50 | 0
in d | Distance | km | 10 | 0 | 100000
out pace | Average pace | min/km | t / d | 2
out speed | Average speed | km/h | d / (t / 60) | 2