Description
Return the indexed symbol from A-Z, a-z, 0-9 followed by +/ for standard or -_ for url.
A positional encoding separates numeric digit values, alphabet symbols and final-block padding. An alphabet lookup is not a whole-stream codec, and character count can differ from the number of source bytes represented.
Return the indexed symbol from A-Z, a-z, 0-9 followed by +/ for standard or -_ for url.
When to use this tool
Use Encoding: Base64 Alphabet Value Symbol when checking one alphabet mapping or bounded encoding-padding term.
How to use the tool and how it works
- Enter value, alphabet. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read result. Expand result to inspect the returned fields.
Require whole value in [0,63] and alphabet standard or url. Return the indexed symbol from A-Z, a-z, 0-9 followed by +/ for standard or -_ for url.1
Alphabet, tail pad bits and written padding depend on the selected base encoding. This tool handles only its stated local component.2
| Input field | Meaning and units | Accepted input |
|---|---|---|
| value | Value | Required. Safe integer. |
| alphabet | Alphabet | Required. Text; one of "standard", "url". Implementation limit: 8192 Unicode code points and 16384 UTF-16 code units. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| result | Object containing the named calculated members below. | Required. Object. |
| result.symbol | Symbol | Calculated result member: string. |
{
"input": {
"value": 62,
"alphabet": "standard"
},
"output": {
"result": {
"symbol": "+"
}
}
}Limitations and assumptions
- This maps one six-bit value only. It does not encode bytes, choose padding policy or verify a complete Base64 string.
- Outputs are nested inside result. Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use the complete codec matching the intended alphabet and padding policy for real payloads and interoperability checks.
References
-
Calculation and input contract: encode/base64-alphabet-value-symbol — tool.io
-
Base16, Base32 and Base64: RFC 4648 — Internet Engineering Task Force
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