In one sentence: Credential stuffing is when criminals use software to try stolen email and password pairs on many other websites.
Why it matters: Think of a thief who steals a key from one building and tries it on the doors of many other buildings. If you reuse a password, one leak can open several accounts. A different password for each account stops one leak from opening your other accounts.
One thing to do: Pick one important account, such as your email, and make sure its password is not used anywhere else.
Related terms: data breach, password manager, account takeover
Learn more: What Is a Password Manager, and How Do You Choose One?
Checked: 25 Oct 2026. Settings screens change. If yours looks different, search the company's help page.
