The developer tools include text compare, encoders and decoders, hash generators, encryption, formatters, converters and generators.
Tools marked Runs in your browser never send your text to our server: everything happens on your device. A few tools need the server, for example bcrypt and Argon2 hashing, OpenSSL ciphers, certificate and CSR tools, the HTTP request tester, the CORS checker and the webhook tester. They say so on the page.
Do not paste live passwords, private keys or customer data into any online tool you do not control.