Base85 Encoder / Decoder
Encode and decode text using Base85 (ASCII85) and RFC 1924 encoding.
About Base85
Base85 encodes binary data using 85 printable ASCII characters. ASCII85 is used in PDF and PostScript. RFC 1924 uses a different character set.
About this tool
Base85 is a binary-to-text encoding system that converts raw data into readable ASCII text, making it ideal for transmitting binary information through text-only channels. Unlike Base64, which expands data by 33%, Base85 is more space-efficient, adding only about 25% to file size—a meaningful advantage when dealing with large payloads like images or document attachments.
To use this encoder, simply choose your encoding variant (ASCII85 is the Adobe standard used in PDFs and PostScript; RFC 1924 is a network-oriented alternative), then select either encode or decode mode. Paste your text or encoded data, click the button, and the result appears with a size comparison showing exactly how much space the encoded version consumes.
Base85 shines in specialized contexts where both efficiency and text-safety matter: PDFs storing embedded fonts, PostScript graphics in print workflows, or networking protocols that need compact representations of binary data. While Base64 remains more universally supported, Base85 is the standard choice when you need to minimize output size without sacrificing portability.
Frequently Asked Questions
Code Implementation
import struct
def encode_ascii85(data: bytes) -> str:
result = []
for i in range(0, len(data), 4):
chunk = data[i:i+4]
padded = chunk.ljust(4, b'\x00')
n = struct.unpack('>I', padded)[0]
if n == 0 and len(chunk) == 4:
result.append('z')
else:
chars = []
for _ in range(5):
chars.append(chr(n % 85 + 33))
n //= 85
result.extend(reversed(chars[:len(chunk)+1]))
return '<~' + ''.join(result) + '~>'
def decode_ascii85(s: str) -> bytes:
s = s.strip()
if s.startswith('<~') and s.endswith('~>'):
s = s[2:-2]
result = bytearray()
i = 0
while i < len(s):
if s[i] == 'z':
result.extend(b'\x00' * 4); i += 1
else:
chunk = s[i:i+5]
n = sum((ord(c) - 33) * (85 ** (4 - j)) for j, c in enumerate(chunk))
result.extend(struct.pack('>I', n)[:len(chunk)-1])
i += 5
return bytes(result)
text = "Hello, World!"
encoded = encode_ascii85(text.encode())
print("Encoded:", encoded)
print("Decoded:", decode_ascii85(encoded).decode())Comments & Feedback
Comments are powered by Giscus. Sign in with GitHub to leave a comment.