What causes "Input cannot be empty." in gchq/CyberChef?

Check for a non-empty string before calling decode.

gchq/CyberChef · error · OperationError

Input cannot be empty.

Error message

Input cannot be empty.

What it means

Thrown by decode() in src/core/lib/Bech32.mjs:239 when the input string is falsy or has length 0. The decoder needs at least an HRP, a separator, and a 6-character checksum to do any work, so an empty input is rejected up front as the first validation gate.

Source

Thrown at src/core/lib/Bech32.mjs:239

    // Check maximum length (90 characters)
    if (result.length > 90) {
        throw new OperationError(`Encoded string exceeds maximum length of 90 characters (got ${result.length}). Consider using smaller input data.`);
    }

    return result;
}

/**
 * Decode a Bech32/Bech32m string
 *
 * @param {string} str - Bech32/Bech32m encoded string
 * @param {string} encoding - "Bech32", "Bech32m", or "Auto-detect"
 * @returns {{hrp: string, data: number[]}} - Decoded HRP and data bytes
 */
export function decode(str, encoding = "Auto-detect") {
    // Check for empty input
    if (!str || str.length === 0) {
        throw new OperationError("Input cannot be empty.");
    }

    // Check maximum length
    if (str.length > 90) {
        throw new OperationError(`Invalid Bech32 string: exceeds maximum length of 90 characters (got ${str.length}).`);
    }

    // Check for mixed case
    const hasUpper = /[A-Z]/.test(str);
    const hasLower = /[a-z]/.test(str);
    if (hasUpper && hasLower) {
        throw new OperationError("Invalid Bech32 string: mixed case is not allowed. Use all uppercase or all lowercase.");
    }

    // Convert to lowercase for processing
    str = str.toLowerCase();

    // Find separator (last occurrence of '1')

View on GitHub (pinned to 4290ea7539)

Solutions

Check for a non-empty string before calling decode.
Provide a clear user-facing error when the input is empty.
Default the variable to '' only if you also short-circuit; better, require a value.
Add a type guard: typeof str === 'string' && str.length > 0.

Example fix

// before
const result = decode(maybeUndefinedAddress);

// after
if (typeof maybeUndefinedAddress !== 'string' || maybeUndefinedAddress.length === 0) {
  throw new Error('A Bech32 address is required.');
}
const result = decode(maybeUndefinedAddress);

Defensive patterns

Strategy: validation

Validate before calling

function requireNonEmptyBech32(str) {
  if (typeof str !== 'string' || str.length === 0) {
    throw new TypeError('A non-empty Bech32 string is required.');
  }
  return str;
}

Type guard

function isNonEmptyString(s) {
  return typeof s === 'string' && s.length > 0;
}

Try / catch

try {
  decode(input);
} catch (e) {
  if (e instanceof OperationError && /Input cannot be empty/.test(e.message)) {
    // prompt the user for an address
  }
}

Prevention

Gate form submissions so an empty address never reaches decode.
Default address variables to null and check before decoding, rather than to undefined.
Validate presence at the UI boundary.

When it happens

Trigger: decode(''), decode(null), decode(undefined). Any code path that passes user input through without a presence check — e.g. an empty form field, a missing config value, or a variable that was never assigned.

Common situations: User submitted an empty form; a variable holding the address was undefined due to a rename or refactor; JSON parsing yielded undefined for a missing field; defensive default of undefined instead of a string.

Related errors

AI-assisted analysis of gchq/CyberChef@4290ea7539 (2026-08-13). Data as JSON: /api/errors/214d77547a7c009e. Report an issue: GitHub.