What Are Ambiguous Characters in Passwords?
Which characters are easily confused in passwords, when to exclude them, and how much strength you lose by doing so.
Some characters look almost identical in many fonts. In passwords that must be read, written down or typed by hand, they cause frustrating login failures.
The usual suspects
| Characters | Confusion |
|---|---|
| O and 0 | Capital letter O vs zero |
| l, 1, I and the pipe | Lowercase L, one, capital i and the pipe symbol |
| Quotes and backtick | Apostrophe, double quote and backtick |
| S and 5, B and 8, Z and 2 | Similar in some handwriting and small fonts |
Our password generator removes the most common look-alikes (O, 0, o, I, l and 1) when you switch on Avoid look-alikes. Its symbol set already leaves out the pipe, quotes and backtick.
When to exclude them
- Wi-Fi passwords shared with guests.
- Temporary passwords given to new staff over the phone.
- Passwords typed on TV remotes or game consoles.
- Codes printed on cards or vouchers.
When not to bother
If a password manager stores and fills the password for you, nobody needs to read it. Keep the full character set for maximum strength.
How much strength do you lose?
Very little. Removing six look-alikes from a pool of 89 characters reduces strength from about 6.48 to 6.38 bits per character. For a 20-character password, that is only about 2 bits less, which you more than win back by adding one extra character.
Other readability tips
- Use a monospaced font when displaying passwords, so each character is distinct.
- Group long codes into blocks of four, such as "Xq7v-Mt9k-R4hp", when they will be typed manually.
- Avoid spaces at the beginning or end of a password; they are invisible and easily lost.
Frequently asked questions
Which look-alike characters should I avoid?
Common look-alike characters are O and 0, l, 1 and I, and some quote marks. Ambiguous characters in passwords only matter when people must read or type them; the generator's "avoid look-alikes" switch removes them.
What are password requirements on most websites?
Typical password requirements include a minimum length (often 8 to 12), and sometimes a mix of uppercase, lowercase, numbers and symbols. Our generator guarantees each selected type appears at least once so passwords pass these rules the first time.
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