Generate a random password with the character sets and length you choose.
Characters are sampled using crypto.getRandomValues(), the browser's cryptographically secure random number generator — not Math.random() — so each character is chosen uniformly at random from your selected character sets.
Entropy = password length × log2(size of the character pool). A longer password, or one drawing from more character sets (uppercase, lowercase, numbers, symbols), produces a larger pool and therefore higher entropy.
No — the password is generated and held entirely in your browser; nothing is sent to a server. Copying it uses your browser's clipboard API, and nothing is saved once you leave or regenerate the page.