These free online security tools cover real cryptography and the classical ciphers you need for puzzles, coursework and CTF challenges. Encrypt a file, decode a certificate, hash a password or generate a six digit code. Nothing you type, drop or select leaves the tab, and every tool runs in your own browser.
Lock a document with the File Encryptor, scramble a message with the Text Encryptor, or spin up a keypair with the RSA Key Pair Generator. The SSL Certificate Decoder pulls the subject, issuer and expiry date out of a certificate, and the CSR Decoder lets you check a request before you send it to a certificate authority. The Bcrypt Generator & Verifier hashes and confirms passwords, and the TOTP Code Generator turns a shared secret into a working six digit code.
On the classical side you get Caesar Cipher, Vigenère Cipher, ROT13 Converter, Rail Fence Cipher, Playfair Cipher, A1Z26 Cipher and a full Enigma Machine Simulator; these are the puzzle, coursework and CTF side of the list. For network work there is a Subnet & CIDR Calculator, IP Address to Binary, Port Number Lookup, a DNS Record Type Reference, a Random MAC Address Generator and a Security Headers Checker.
The file you drop on the File Encryptor is read by your own browser through the Web Crypto API, so there is no file size cap and no server holding a copy of your data later. The private key from the RSA Key Pair Generator is created on your machine and never transmitted, and your TOTP seed is never written to a log. No account, no email step, no cookie and no upload queue.
They are safe as long as the encryption actually runs in your browser instead of on the site's server. Look for pages that describe client side or Web Crypto processing, and avoid any tool that asks you to upload a file and then hands you a download link, because that means your plaintext, and often your password, passed through someone else's machine. Every tool on this page runs locally, so you can load it, disconnect from the network and it still works.
Yes. The File Encryptor reads your file with the browser's own file and Web Crypto APIs, derives a key from the password you type, and writes the encrypted result straight back to your downloads folder. Because the bytes never cross the network there is no upload progress bar, no server imposed size limit, and no temporary copy sitting in a storage bucket after you close the tab. The same applies to the Text Encryptor.
No. Caesar Cipher, Vigenère Cipher, Rail Fence, Playfair, A1Z26 and even the Enigma Machine Simulator are historical ciphers that a modern computer breaks in seconds, often through frequency analysis alone. Use them for puzzles, CTF challenges, escape rooms and teaching how cryptography developed. For anything you genuinely need kept private, use the File Encryptor or Text Encryptor, which are built on AES, or the RSA Key Pair Generator for public key work.