FASTBASE64(1) User Commands FASTBASE64(1)

fastbase64 - base64 encode/decode data and print to standard output

fastbase64 [-Ddh] [-b num] [-i in_file] [-o out_file]

fastbase64 encodes or decodes base64 data using the high-performance simdutf library. By default, it encodes binary input to base64 output. On large files, it can be several times faster than standard base64 tools. If a second filename is provided, it is used as the output file. Otherwise, output goes to standard output.

break encoded output up into lines of length num (default 0, meaning no breaks)
decode input
display this message
input file (default: "-" for stdin)
output file (default: "-" for stdout)
same as -b
encode input (default)
when decoding, ignore non-alphabet characters
output version information and exit

fastbase64 -i myfile.txt
fastbase64 -d -i encoded.txt
fastbase64 -b 76 -i myfile.txt

base64(1), fastbase64.coreutils(1), iconv(1)

Written by the simdutf development team.

March 2026 simdutf