IDN / Punycode Converter

Internationalized Domain Names (IDN) let labels include non-ASCII characters so brands can use local scripts. The DNS itself still transports ASCII on the wire, so IDNA defines Punycode encodings commonly recognized by the xn-- prefix. Converters help when a control panel shows Unicode while logs, certificate CSRs, dig output, or email headers show Punycode.

Operational tips

Always confirm which form your certificate authority, email provider, and DNS host expect. Mixed tooling is a frequent source of “domain not found” confusion: you register Unicode in one UI, then paste ASCII into another without realizing they are the same name. After converting, verify live DNS with All DNS Records using the ASCII form resolvers understand.

Email is especially sensitive. Some older MTAs mishandle IDN in ways that look like deliverability bugs. Prefer well-supported ASCII for infrastructure hostnames even when the marketing domain is IDN.

How DNS Checkers converts

We use PHP’s Intl IDNA APIs (UTS #46) when available. Invalid labels fail closed with an error instead of guessing. Emoji and unusual symbols may convert if they form valid IDNA labels, but registrar support varies — always verify registration and DNS hosting independently.

Security

Homograph attacks abuse lookalike characters across scripts. Conversion alone does not tell you whether a name is malicious; it only shows encodings. Combine IDN checks with careful link inspection and, for your own zones, stick to deliberate character sets your users expect.

Related: DNS Propagation, Domain Health, and the blog.

Certificates, cookies, and redirects

TLS certificates must match the names clients request. Some issuers display Unicode in dashboards while the CSR contains Punycode. Confirm both. Likewise, cookie Domain attributes and HSTS preload lists are ASCII-oriented; publishing mismatched forms can create subtle login loops. When migrating an IDN site, update redirects so both encodings converge on one canonical HTTPS URL to avoid duplicate-content SEO issues.

Search engines generally understand IDN, but analytics tools sometimes split traffic across encodings. Normalize reporting to one form. DNS Checkers conversion plus DNS lookups give you a quick lab for verifying that apex and www variants resolve consistently before you announce a campaign on a localized brand name.

If Intl IDN functions are missing on a minimal PHP build, this converter will say so instead of silently failing. That honesty matches the rest of DNS Checkers: better a clear error than a plausible wrong string.

Bookmark both encodings in your migration ticket so future you does not waste an hour wondering why dig and the browser disagree about a name that is actually identical.