ROT13 & Caesar cipher

Client

Classic Latin letter rotation: ROT13 for a fixed 13-step swap, or Caesar with any shift from 0 through 25. Helpful for puzzles, teaching, and quick redaction of readable Latin text—runs locally in your browser.

Using this page

Type or paste text in the input box. Choose ROT13 for the standard puzzle transform, or Caesar and set a shift. The output updates as you edit. For related encodings (Morse, Unicode escapes, HTML entities), open the Encoding workspace or jump to Morse, HTML entities, and Unicode escapes.

All local. Only Basic Latin letters A–Z and a–z are rotated; digits, spaces, accents, and symbols stay as-is. For secrecy use real crypto—this is a classic puzzle transform.

Input

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ROT13 is a 13-position shift: applying it twice returns the original Latin letters. Caesar uses any shift 0–25; decode by using 26 minus the forward shift, or re-type ciphertext with the matching reverse shift.

Mode

Output

Gur Dhvpx oebja sbk 123. Pnsé anïir?

Common use cases

  • Obscure spoiler text or forum punchlines with ROT13—readers decode by running the same transform again.
  • Try Caesar shifts when learning classical ciphers or solving light CTF / puzzle challenges.
  • Compare letter patterns before and after rotation when teaching how frequency analysis breaks simple ciphers.
  • Pair with Morse or Unicode escape tools when experimenting with stacked text transforms in the encoding cluster.

Common mistakes to avoid

  • Treating ROT13 as secrecy

    ROT13 and Caesar are reversible by inspection. Do not use them to protect real secrets—use authenticated encryption and key management instead.

  • Expecting non-Latin letters to shift

    Only A–Z and a–z rotate. Accented letters, Cyrillic, CJK, emoji, and digits are left unchanged so the transform stays predictable.

  • Wrong shift when decoding Caesar

    Decryption is rotation by 26 − k (mod 26). If the output looks like noise, check the shift value and that the input used the same alphabet rules.

FAQ

Why is ROT13 its own inverse?

Thirteen is half of the 26-letter Latin alphabet, so shifting twice returns each letter to its original position.

How do I decode Caesar ciphertext?

Use the same page with shift 26 − k, or paste the ciphertext and apply a forward shift until readable—this tool shows the result live.

Is text sent to a server?

No. Input and output stay in your browser tab.

Can agents prefill the text field?

Yes. Same `q` / `qb` pattern as other single-field tools; optional `mode=rot13|caesar` and `shift=0..25` set defaults after load.

Common search terms

Phrases people search for that match this tool. See the full long-tail keyword index.

  • rot13 encoder online
  • caesar cipher shift browser
  • rot 13 decode text free
  • latin letter rotation a-z

More tools

Related utilities you can open in another tab—mostly client-side.