basenc — Base64 and URL-Safe Encoding

basenc (GNU coreutils) encodes and decodes data in various base formats. Its key advantage over the older base64 utility is native support for URL-safe base64 (--base64url), which replaces + and / with - and _ to avoid URL-escaping headaches. ¹

Common operations

# Encode to standard base64
echo "$STRING" | basenc --base64
 
# Encode to URL-safe base64
echo "$STRING" | basenc --base64url
 
# Decode from standard base64
echo "$BASE64_STRING" | basenc -d --base64
 
# Decode from URL-safe base64
echo "$BASE64_STRING" | basenc -d --base64url

Supported encodings

basenc supports more than just base64:

Encoding	Flag
Base64	--base64
URL-safe base64	--base64url
Base32	--base32
Base32 hex	--base32hex
Base16 (hex)	--base16
Base2 (binary)	--base2msbf, --base2lsbf
Z85	--z85

When to prefer basenc over base64

• URL-safe output: --base64url avoids the need for post-processing tr '+/' '-_'. ²
• Multiple formats: one tool for base32, base16, and base64.
• Consistency: basenc is the modern coreutils frontend; base64 is maintained for compatibility. ³

Sources

• basenc(1) — Linux manual page
• basenc invocation (GNU Coreutils 9.11)

Related: powershell-base64-encoding, linux-reconnaissance-commands

Footnotes

1. basenc(1) — Linux manual page ↩

2. basenc invocation (GNU Coreutils 9.11) ↩

3. basenc invocation (GNU Coreutils 9.11) ↩