Javascript base64 encoder/decoder may be used to to prepare binary data for network transfer.
Binary data is reprensented by octets (bytes) each carrying one value from 0 to 255. Such data is not network-safe since some values may have special meaning and won't be transferred as is. Base64 is a method to re-pack bytes using only values from 0 to 64 (hence the name). This is achieved using lowercase and uppercase latin letters (26 + 26), digits (10), along with plus and slash signs (2), totalling 64. Since 8-bit value cannot fit into 6-bit value, three adjacent octets (3 x 8 = 24) are regrouped into four 6-bit blocks (4 x 6 = 24), leading to 25% data size growth.