Caesar Cipher & ROT13

About the Caesar Cipher & ROT13

The Caesar cipher shifts every letter a fixed number of places along the alphabet — Julius Caesar reportedly used a shift of three. It's a favourite for puzzles, escape rooms, geocaching and teaching the basics of cryptography. ROT13, a shift of 13, is its own inverse and is still used to hide spoilers online.

How to use it

1. Type or paste your text.
2. Choose a shift, or tap ROT13.
3. To decode, tap Reverse shift and read the original.

Tips and good to know

• Upper and lower case are preserved.
• Digits, spaces, punctuation and accented letters are left unchanged.
• A shift of 26 returns the original text.
• With only 25 possible shifts, anyone can break it in seconds — never use it to protect real secrets.

About text & writing tools

Writers, students, marketers and developers spend a surprising amount of time doing mechanical things to text: counting words for a brief, fixing an accidental caps-lock paragraph, removing duplicate lines from an export, or spotting what changed between two drafts. None of these tasks need artificial intelligence — they need a precise, predictable tool.

Every text tool here runs instantly as you type and never stores what you paste. That makes them suitable for unpublished manuscripts, client copy and confidential notes. Where a tool makes a judgement call — such as how it defines a 'word' or a 'sentence' — the guide below explains the rule so you can trust the number you report.

Counting and comparing text sounds simple, but the rules matter. Different systems disagree on whether a hyphenated word is one or two words, whether an emoji is one character or several, and where a sentence ends after an abbreviation. Publishers, universities and social networks each publish their own limits, so when a number really matters — a grant application, a journal abstract, an SEO title — check which counting rule the reader uses. Our tools follow the conventions of mainstream word processors and browsers and explain any judgement calls on each page, so that you can report a figure with confidence and reproduce it later.

Popular ways people use text & writing tools

• Checking an essay, cover letter or grant application against a strict word or character limit.
• Comparing two versions of a contract clause or policy to see exactly what the other side changed.
• Cleaning a mailing list exported from several sources so nobody receives the same email twice.
• Turning article titles into clean, readable URL slugs when publishing posts in a content system.
• Fixing a paragraph that was accidentally typed with caps lock on without retyping it from scratch.

How we build and test our free tools

Every tool in this collection is built and tested by The Curator team. Before a tool is published we check it against known reference results — textbook loan schedules, standard test vectors for hashes, sample files for conversions — and we re-check it whenever browsers change. Each page explains the method so you can verify the answer yourself rather than take it on trust.

The tools run as JavaScript inside your browser tab. When you choose a file, your browser reads it from your disk into memory; the tool processes it and gives you the result as a download. No copy is sent to us or to anyone else, and nothing is kept after you close the tab. That is why these tools are safe for personal documents, and why they keep working on a slow or interrupted connection once the page has loaded.

The collection is free because it is supported by advertising on these guide pages. We never charge for a tool, never add watermarks and never sell what you type. If something doesn't work as described, or you would like a tool we don't have yet, please contact us — new tools are added in regular batches based on what readers ask for.

Frequently asked questions

How do I crack an unknown shift?

Try shifts 1 to 25 and look for readable words; or look for the most common letter, which in English is often E.

Can I use negative shifts?

Yes, a negative shift moves letters backwards.

Is my input stored or sent anywhere?

No. The calculation runs entirely in your browser tab and disappears when you close it.

Is the Caesar Cipher & ROT13 really free?

Yes. There is no account, no trial and no watermark. The Curator is supported by advertising on its guide pages, never by charging for tools or selling your data.

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