Text Leading Trailing BOM Distinction Tool

Description

Return leading and trailing U+FEFF flags and zero-based UTF-16 interiorIndices excluding both endpoints.

Text positions can be measured in UTF-16 code units, Unicode code points, grapheme clusters, or modeled display columns. These coordinates are not interchangeable. Invisible markers and delimiter policies can also affect interpretation even when a string looks unchanged, so the chosen representation needs to stay explicit.

Return leading and trailing U+FEFF flags and zero-based UTF-16 interiorIndices excluding both endpoints.

When to use this tool

Use Text Leading Trailing BOM Distinction when you need the stated marker, coordinate, delimiter, or normalization operation under an explicit text representation.

How to use the tool and how it works

Enter text. Use the units and conventions below.
Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
Read leading, trailing, interiorIndices. Inspect leading, trailing before interpreting the associated values.

Return leading and trailing U+FEFF flags and zero-based UTF-16 interiorIndices excluding both endpoints.^[1]

Input field	Meaning and units	Accepted input
text	Text	Required. Text; maximum UTF-16 length 8192.

Output field	Interpretation	Returned shape
leading	Leading	Required. Boolean.
trailing	Trailing	Required. Boolean.
interiorIndices	Interior Indices	Required. Array of safe integer; maximum items 256.

json

{
  "input": {
    "text": "a"
  },
  "output": {
    "leading": true,
    "trailing": true,
    "interiorIndices": []
  }
}

Limitations and assumptions

A single U+FEFF is both leading and trailing with no interior occurrence. Position alone does not establish an actual byte-order mark, encoding, or whether removal preserves meaning.
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

Choose the coordinate system required by the consumer. Use a full parser, renderer, or segmentation method when a local marker or delimiter rule cannot determine the complete text behavior.

References

Calculation and input contract: text/text-leading-trailing-bom-distinction — tool.io

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