gchq/CyberChef · error · OperationError

Character at position ${i} exceeds Latin-1 range (0-255). On

Error message

Character at position ${i} exceeds Latin-1 range (0-255).
Only ASCII and Latin-1 characters are supported.

What it means

TextIntegerConverter's text-to-BigInt path interprets each character as a single byte (big-endian). Any character whose code point exceeds 255 — i.e. anything outside Latin-1 such as emoji, CJK characters, or accented characters above U+00FF — is rejected, because it cannot fit in one byte of the resulting integer.

Source

Thrown at src/core/operations/TextIntegerConverter.mjs:22

 * @license Apache-2.0
 */

import Operation from "../Operation.mjs";
import OperationError from "../errors/OperationError.mjs";

/* ---------- helper functions ---------- */

/**
 * Convert text to BigInt (big-endian byte interpretation)
 */
function textToBigInt(text) {
    if (text.length === 0) return 0n;

    let result = 0n;
    for (let i = 0; i < text.length; i++) {
        const charCode = BigInt(text.charCodeAt(i));
        if (charCode > 255n) {
            throw new OperationError(
                `Character at position ${i} exceeds Latin-1 range (0-255).\n` +
                "Only ASCII and Latin-1 characters are supported.");
        }
        result = (result << 8n) | charCode;
    }
    return result;
}

/**
 * Convert BigInt to text (big-endian byte interpretation)
 */
function bigIntToText(value) {
    if (value === 0n) return "";

    const bytes = [];
    let num = value;

    while (num > 0n) {

View on GitHub (pinned to 4290ea7539)

Solutions

1. Strip or replace non-Latin-1 characters before conversion.
2. Convert the input to UTF-8 bytes first via a 'To Hex' / UTF-8 path, then treat the bytes as the integer.
3. Restrict input to ASCII / Latin-1 (code points 0-255).

Example fix

// before: input = "café\u20AC"  (€ is U+20AC > 255) -> throws at the € position
// after:  input = "cafe"         (ASCII only)            -> converts successfully

for (let i = 0; i < text.length; i++) {
  if (text.charCodeAt(i) > 255) throw new Error(`Non-Latin-1 char at ${i}`);
}

const isLatin1 = text => [...text].every(c => c.charCodeAt(0) <= 255);

try { textToBigInt(text); }
catch (e) { if (/Latin-1/.test(e.message)) { text = text.replace(/[^\u0000-\u00ff]/g, ""); } else throw e; }

When it happens

Trigger: Passing input containing characters with charCodeAt > 255 to the Text -> BigInt direction. Examples: emoji (U+1F600), Chinese characters, the Euro sign (U+20AC), or curly quotes.

Common situations: Pasting rich/Unicode text from a word processor; receiving UTF-8 multibyte text where the source intent was ASCII; mixing encodings.

Related errors

• Unknown Normalisation Form
• Invalid Base64 alphabet length (${alphabet.length}): ${alpha
• Byte length must be a positive integer
• unexpected character encountered: "${character}"
• Invalid custom CRC arguments

AI-assisted analysis of gchq/CyberChef@4290ea7539 (2026-08-13). Data as JSON: /api/errors/fa9501d6eac2bef3. Report an issue: GitHub.