Punycode converter: turn bücher.de into xn--bcher-kva.de and back
In short: Paste domains with accents or non-Latin letters, or xn-- names, and get both forms, the length DNS sees, and warnings for invalid characters and mixed scripts. Limit: The full IDNA2008 and UTS 46 mapping tables aren't applied; registry rules vary.
A Punycode converter turns an internationalised domain name such as bücher.de into the ASCII form DNS stores, xn--bcher-kva.de, and decodes xn-- names back to Unicode. Paste one name or up to 100 (500 after a Google sign-in): each gets both forms, its length in DNS, the writing systems used, and a warning for emoji, invalid characters or mixed scripts.
Price: this tool is free. Checking a whole email list is from $9/mo, and the first 100 checks are free with Google, no card. See pricing
Sample result
bücher.example is stored in DNS as xn--bcher-kva.example.
- Domain
- bücher.example
- Punycode
- xn--bcher-kva.example
- Length in DNS
- 21
What this means for you
Get the form DNS, certificates and mail servers use, and catch names that won't register.
- Unicode to xn-- and back
- Label and name lengths checked
- Emoji and mixed scripts flagged
- 100 names a run, 500 when signed in
- Punycode
- IDN
- xn--
By SimpleVerifier Team · Last updated · Runs in your browser; nothing you paste is sent to us
Converting a whole list of names or addresses?
- Over 500 names? Run them in batches of 500 when signed in and download the CSV after each.
- See which converted names are free to register with the bulk domain availability checker.
- Mailing addresses on these domains? Check the list at /verify. The first 100 email checks are free with a Google sign-in, no card.
How do I convert a domain name to Punycode?
- Paste one domain or a list, one per line, in either form: bücher.de or xn--bcher-kva.de. URLs and email addresses are trimmed to the domain.
- Press Convert. It runs in your browser; nothing is uploaded.
- Read each name's Unicode and Punycode forms, its length in DNS, and any warning.
- Copy either column or download the CSV.
Example
- You enter
- Four names:
bücher.example,xn--mnchen-3ya.example,аpple.example(with a Cyrillic а) and☕.example. - You get
bücher.exampleConverted:xn--bcher-kva.example.xn--mnchen-3ya.exampledecodes tomünchen.example.аpple.exampleCheck this: it mixes Latin and Cyrillic letters, the pattern of look-alike domains; its DNS form isxn--pple-43d.example.☕.exampleInvalid: IDNA2008 doesn't allow emoji. Copy either column or download the CSV.- Limits
- Up to 100 names a run without an account and 500 when signed in with Google. Runs in your browser.
What is Punycode?
DNS only stores letters a to z, digits and hyphens. IDNA lets a domain use other letters by encoding each such label with Punycode (RFC 3492) and prefixing it with xn--. Browsers and mail apps show the Unicode form, but DNS, certificates and mail servers see the xn-- form. A label may be 63 characters in that form and the whole name 253 (RFC 1035), so a short name in Unicode can be longer than it looks.
Before encoding, each label is lower-cased and normalised to Unicode NFC, so Bücher and a u plus combining umlaut give the same result.
What does the converter warn about?
Characters a domain can't hold: emoji, which IDNA2008 disallows and most registries refuse, and symbols other than letters, digits and hyphens. Labels that start or end with a hyphen, or have hyphens in the third and fourth places without being xn--, which RFC 5891 reserves. Labels over 63 characters once encoded. And labels that mix writing systems, such as a Cyrillic а among Latin letters: that's how look-alike (homograph) domains are built, and browsers may show such names in xn-- form.
Who uses this tool, and for what?
- Domain investors
- Get the xn-- form of IDN names to check and register them.
- Security teams
- Decode xn-- names from logs and spot mixed-script look-alikes.
- Developers
- Convert names for DNS records, certificates and allow-lists that need ASCII.
- Email teams
- Normalise IDN domains in a list to the form mail servers use.
What can’t this tool tell you?
- The full IDNA2008 and UTS 46 mapping tables aren't applied; registry rules vary.
- It doesn't check whether a name is registered; use the availability checker for that.
- Mixed-script warnings cover common scripts; it isn't a complete confusables check.
- Up to 100 names a run without an account and 500 signed in.
Common questions
- Does the converter apply every IDNA rule?
- No. It applies Punycode, NFC and the length, hyphen and character checks above, but not the full IDNA2008 or UTS 46 tables. Each registry also has its own list of allowed characters, so a name that converts here can still be refused.
- Can I use an emoji domain?
- A few ccTLD registries accept them, but IDNA2008 disallows emoji, most registries refuse them and many apps won't link them. The converter still shows the xn-- form and flags it.
- Why is Japanese marked as several scripts?
- Japanese mixes Han, Hiragana and Katakana by design, and Latin next to Chinese, Japanese or Korean is common, so those mixes aren't flagged.
- Do email addresses work on IDN domains?
- The domain part does, through its xn-- form. A non-ASCII local part needs SMTPUTF8 (RFC 6531) support on every server on the way.
- Is anything uploaded?
- No. The conversion runs in your browser.
- Is the Punycode converter free?
- Yes, it's a free tool with no card. 100 names a run, or 500 after a free Google sign-in.
Sources
You audited one domain. Cold outreach means thousands.
This tool checks a domain you type in. It will not tell you which addresses at that domain are real.
- Bulk mailbox verification with real SMTP checks
- The email finder — name plus company to a verified address
- Website enrichment for emails, owner names and socials
Plans from $9 a month, cancel anytime, no contract. Sign in with Google and your first 100 email checks are free, no card. The free tools stay free either way.