Description
Extract a private-use tail after the first x subtag under a limited language-tag shape rule.
Identifier validation can involve several distinct questions: whether text has the expected shape, whether a checksum is consistent, and whether an authority actually assigned the identifier. Formatting and field extraction address narrower questions. Each result must be read according to the particular property the tool checks.
Extract a private-use tail after the first x subtag under a limited language-tag shape rule.
When to use this tool
Use BCP 47 Private Use Tail Token when you need the particular shape, formatting, field, or checksum property as one explicit stage in an identifier workflow.
How to use the tool and how it works
- Enter tag. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read privateUse, present. Inspect present before interpreting the associated values.
Require nonempty hyphen-separated ASCII alphanumeric parts. Find the first part equal to x ignoring case; if present require at least one following part and each remaining part no longer than eight characters. Return privateUse and present.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| tag | Tag | Required. Text; maximum UTF-16 length 8192. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| privateUse | Private Use | Required. Array of Text; maximum UTF-16 length 8192.; maximum items 256. |
| present | Present | Required. Boolean. |
{
"input": {
"tag": "en-US-x-acme"
},
"output": {
"privateUse": [
"acme"
],
"present": true
}
}Limitations and assumptions
- The prefix before x is not fully validated as BCP 47 and private-use text preserves case. The tool does not consult a language registry or assign interoperable meaning to private subtags.
- The field tables state structural bounds; the mechanics also specify cross-field constraints. Malformed inputs and unsupported domains cause errors. A successful false flag, empty branch value, or zero placeholder has the meaning stated above and is distinct from an input error.
Alternative or Complementary methods
Use a complete format and checksum validator when required, then consult the issuing registry or verification process for assignment and identity. Preserve meaningful leading zeros as text.
References
Similar or alternative tools
- BCP 47 Extlang Subtag Boundary
Split a language-tag-shaped string into language, up to three extlang-shaped parts, and a remainder.
- Ark Qualifier Leading Separator Check
Return valid when qualifier is empty or starts with slash or dot.