Letters only, still random
Some systems only accept letters, and letters are the easiest characters to type on any keyboard layout, phone or TV remote. With 52 possible letters, each character adds about 5.7 bits, so the default 20 characters give about 114 bits of entropy.
Keep it long
Without digits and symbols, length carries the whole load. Stay at 16 characters or more for important accounts. Turn on “Avoid look-alikes” if you will type the password from paper, which removes I, l and O.
Frequently asked questions
Will letters-only passwords pass most site rules?
Sites that require a number or symbol will reject them. Use the main password generator for those sites and keep this one for systems that need letters only.
Is mixing upper and lowercase enough?
Mixed case doubles the character set compared with lowercase alone, adding one bit per character. Most of the strength still comes from length.