Question 1

What is ASCII85 (Base85)?

Accepted Answer

ASCII85, also called Base85, encodes binary data into printable ASCII characters using an 85-character alphabet. It is more compact than Base64, encoding 4 bytes into 5 characters instead of 4 into 6.

Question 2

What are the different ASCII85 variants?

Accepted Answer

Common variants include Adobe ASCII85 (used in PDF and PostScript, wrapped in <~ ~>), btoa (Unix tool), Z85 (ZeroMQ, used in IPv6) and RFC 1924. They differ in alphabet characters and framing.

Question 3

Is ASCII85 more efficient than Base64?

Accepted Answer

Yes. ASCII85 encodes 4 bytes into 5 characters (25% overhead), while Base64 encodes 3 bytes into 4 characters (33% overhead). ASCII85 produces smaller output.

Question 4

Where is ASCII85 used?

Accepted Answer

ASCII85 is used in PDF and PostScript binary data streams, Git binary patches, IPv6 address representation (RFC 1924), and ZeroMQ Z85 encoding for CurveZMQ keys.