Punycode Converter

Convert Unicode domains and Punycode online

This IDN converter turns Unicode U-labels into ASCII A-labels, decodes valid xn-- labels, processes full domains one label at a time, preserves valid ASCII labels, applies UTS #46 nontransitional, STD3 rules validation with Python idna 3.18, supports recognized Unicode domain separators, shows changed and unchanged labels, and processes input on the server.

Unicode domain to Punycode example

café.example converts to xn--caf-dma.example. Only the first label changes.

Punycode to Unicode example

xn--caf-dma.example decodes to café.example. The xn--caf-dma A-label is decoded and the ASCII example label remains unchanged.

What does xn-- mean?

xn-- marks an ASCII A-label containing Punycode. It lets a Unicode domain label be represented with ASCII characters. The prefix applies to an individual label, so café becomes xn--caf-dma while an ASCII label such as example usually remains unchanged. Not every string beginning with xn-- is valid.

Punycode vs IDNA

Punycode is an encoding algorithm. IDNA defines domain mapping, validation and label conversion, including U-labels and A-labels. Full domain conversion requires label-aware processing, so this tool uses the configured IDNA implementation rather than encoding the entire domain as one raw Punycode string.

Domain labels and per-label conversion

Domains consist of labels separated by periods. Each label is validated separately, Unicode labels may become xn-- A-labels, ASCII labels can remain unchanged, and the converted domain is rebuilt with ASCII periods. Recognized separators are ., 。, ． and ｡; non-ASCII separators are reported when they are mapped.

IDNA validation errors

The converter reports label-specific errors for empty labels, leading or trailing hyphens, invalid xn-- payloads, disallowed code points, invalid joiner context, bidirectional rule failures, labels that are too long and domains that exceed the supported DNS length. Invalid labels are not silently removed or fixed.

Unicode domains and spoofing risks

Punycode conversion only changes how an internationalized domain is represented. It does not confirm ownership, registration, trust, browser display behavior or phishing intent.

For Unicode lookalikes, use the Confusable Character Detector. To review writing systems, use the Mixed Script Detector.

How to use the converter

1. Choose Unicode domain to Punycode or Punycode to Unicode.
2. Paste a full domain name or individual label.
3. Run the conversion.
4. Review the converted domain and each label’s validation result.
5. Inspect warnings before using the result in security-sensitive contexts.
6. Copy the domain or download the conversion report.

Privacy and server processing

The submitted domain or label is sent to UnicodeNow for IDNA and Punycode conversion. Input is processed securely and is not intentionally retained after the request completes.

Do not submit passwords, private keys, access tokens or other sensitive information.

Common use cases

• Convert an internationalized domain to its ASCII DNS form.
• Decode an xn-- domain label into readable Unicode.
• Inspect which labels changed during conversion.
• Validate IDNA labels before storing or displaying them.
• Debug domain-processing and email-validation workflows.
• Review internationalized domains before manual security analysis.
• Create IDNA and Punycode test fixtures.
• Compare Unicode and ASCII representations of the same domain.

How Punycode conversion works

The server separates the domain into labels and applies UTS #46 nontransitional, STD3 rules through Python idna 3.18. Unicode labels are converted to ASCII A-labels beginning with xn--, while valid ASCII labels remain unchanged.

Frequently asked questions