These security tools run in the browser. The values you generate or paste are not uploaded, and none of them needs an account. Closing the page drops the text.
UUID Generator asks the browser for a version 4 UUID. If that call is missing, the page stops rather than inventing a weaker identifier. Password Generator draws from the character sets you tick, using the cryptographic generator, and shows the password only so you can copy it. Password Strength scores the shape of what you type. A high score is not a search of leaked passwords.
Base64 Encode and Decode and URL Encoder convert text in the page, including Unicode. Hash Generator computes SHA-256. It does not offer MD5 on this result. JWT Decoder prints the header and the payload of a compact token. The JWT signature is not verified, and the page will not ask you for a key.
Use a generated password for a secret you want to keep, and a UUID for a label rather than for a password. The privacy page explains the optional ad and analytics cookies. These tools do not create an account.
Tools
Read the privacy page for what each check sends.