For GNU grep in particular, no, using a UTF-8 locale can significantly slow it down: $ time LC_ALL=C grep -E '^\w{30}$' OpenSubtitles2018.raw.sample.en -c

For GNU grep in particular, no, using a UTF-8 locale can significantly slow it down: $ time LC_ALL=C grep -E '^\w{30}$' OpenSubtitles2018.raw.sample.en -c 3 real 0.808 user 0.744 sys 0.063 maxmem 10 MB faults 0 $ time LC_ALL=en_US.UTF-8 grep -E '^\w{30}$' OpenSubtitles2018.raw.sample.en -c 4 real 20.064 user 19.982 sys 0.077 maxmem 10 MB faults 0 Where as ripgrep is just Unicode aware by default, and still about as fast as the ASCII only variant of GNU grep above: $ time rg '^\w{30}$' OpenSubtitles2018.raw.sample.en -c 4 real 1.163 user 1.132 sys 0.030 maxmem 916 MB faults 0