# writeUint64

`import { writeUint64 } from "destack:bytes";`

Write one unsigned 64-bit integer.

```ds title="writeUint64"
export function writeUint64(bytes: &'a exclusive [uint8], offset: usize, value: uint64, order?: "bigEndian" | "littleEndian"): void
```

[language/library/src/bytes/bytes.ds:103:110](https://github.com/destack-sh/destack/blob/main/language/library/src/bytes/bytes.ds#L103-L110)