clockworklabs/SpacetimeDB · error · Error

Uint8Array is not 16 bytes long: ${array}

Error message

Uint8Array is not 16 bytes long: ${array}

What it means

uint8ArrayToU128 interprets the bytes as a little-endian 128-bit integer via BinaryReader.readU128, so exactly 16 bytes are required; any other length throws. It also backs hexStringToU128, so a hex string decoding to the wrong byte count surfaces here too.

Source

Thrown at crates/bindings-typescript/src/lib/util.ts:48

  // Check all keys and compare values recursively
  for (const key of keys1) {
    if (!keys2.includes(key) || !deepEqual(obj1[key], obj2[key])) {
      return false;
    }
  }

  return true;
}

export function uint8ArrayToHexString(array: Uint8Array): string {
  return Array.prototype.map
    .call(array.reverse(), x => ('00' + x.toString(16)).slice(-2))
    .join('');
}

export function uint8ArrayToU128(array: Uint8Array): bigint {
  if (array.length != 16) {
    throw new Error(`Uint8Array is not 16 bytes long: ${array}`);
  }
  return new BinaryReader(array).readU128();
}

export function uint8ArrayToU256(array: Uint8Array): bigint {
  if (array.length != 32) {
    throw new Error(`Uint8Array is not 32 bytes long: [${array}]`);
  }
  return new BinaryReader(array).readU256();
}

export function hexStringToUint8Array(str: string): Uint8Array {
  if (str.startsWith('0x')) {
    str = str.slice(2);
  }
  const matches = str.match(/.{1,2}/g) || [];
  const data = Uint8Array.from(
    matches.map((byte: string) => parseInt(byte, 16))

View on GitHub (pinned to 524b4487d9)

Solutions

1. Validate array.length === 16 before calling
2. Check the source hex string: after stripping '0x' it must be exactly 32 hex chars
3. Use the matching converter - uint8ArrayToU256 for 32-byte values

Example fix

// before
const v = uint8ArrayToU128(identityBytes); // identityBytes is 32 bytes -> throws

// after
const v = uint8ArrayToU256(identityBytes); // 32-byte value
// or slice the correct 16 bytes: uint8ArrayToU128(identityBytes.slice(0, 16))

function isU128Bytes(array: Uint8Array): boolean {
  return array.length === 16;
}
// if (!isU128Bytes(bytes)) throw new TypeError(`expected 16 bytes, got ${bytes.length}`);

When it happens

Trigger: Passing a Uint8Array whose length is not 16 directly, or a hex string that decodes to a non-16-byte array (e.g. a 64-char identity/address hex) through the hex-to-u128 helpers that call this function.

Common situations: Reusing 32-byte Identity/address bytes for a u128 field; slicing arrays with wrong offsets; hex strings with odd length or without zero padding.

Related errors

• Uint8Array is not 32 bytes long: [${array}]
• UUID v4 requires 16 bytes
• Invalid UUID: must be between 0 and `MAX_UUID_BIGINT`
• Index '${indexLabel}' on table '${tableLabel}' must define a
• Timestamp is outside of the representable range of JS's Date

AI-assisted analysis of clockworklabs/SpacetimeDB@524b4487d9 (2026-08-16). Data as JSON: /api/errors/6f6af5cb61192ca1. Report an issue: GitHub.