# bytes/len Byte length of a string. `len` counts CODEPOINTS; use `bytes/len` for buffer sizing and byte offsets on binary data (fs/read bodies, crypto, encoded blobs) — byte math must never drift on data that happens to contain valid UTF-8 runs. ## Syntax

[bytes/len $s]

## Examples

[len "a中c"]          # 3  (codepoints)
[bytes/len "a中c"]    # 5  (bytes)

## Returns Number. ## See Also `bytes/slice`, `byte-at`, `len`