Atbash cipher

This capability takes a non-empty text field, returns the transformed string with a count of mirrored letters, and rejects empty input with a clear invalid_input error.

How Atbash works and what the response contains

Atbash mirrors each letter by position: the first letter of the alphabet maps to the last, the second to the second-last, and so on. Uppercase letters A through Z map to Z through A; lowercase letters a through z follow the same reflection within their own alphabet so case is preserved. Characters outside those ranges—digits, punctuation, whitespace, emoji, and non-Latin scripts—pass through unchanged so messages keep their shape and spacing. Send a JSON body with the required string field text set to any non-empty message; aliases input, value, and s are accepted when clients reuse older form names. Empty strings fail immediately with invalid_input because there is nothing meaningful to transform and the product promise is a real substitution result. On success the response includes result with the transformed text, method equal to atbash so downstream code can branch without sniffing shapes, length equal to the input character count, and letters_mirrored counting how many A–Z or a–z units actually flipped. Identical inputs always produce identical JSON because the path is pure character arithmetic with no network, no random seed, and no wall clock. Use letters_mirrored when you want to assert that punctuation-heavy strings still processed correctly without inventing a second mode field.

Encode, decode, validation rules, and common pitfalls

Missing text, non-string text, or an empty string all raise invalid_input and are not charged on the prepaid API. Whitespace-only strings that still have length greater than zero are accepted; only letters mirror, so a string of spaces returns itself with letters_mirrored equal to zero.

API usage, pricing, classroom workflows, and practical limits

Call the free in-browser atbash cipher for puzzle drafting, biblical-cipher demos, lecture slides, and one-off checks without writing a one-liner in every language. A typical classroom workflow shows students that mirroring the alphabet twice returns the original message, then contrasts that involution with a true keyed monoalphabetic cipher later in the syllabus. Support playbooks can reverse lightly obfuscated ticket notes that staff intentionally wrote in Atbash. Pair with Base64 or URL-encoding tools only when a later transport step needs a different alphabet—keep Atbash on its own landing so SEO intent stays sharp. Use the prepaid KIT API when a backend, serverless function, tutoring platform, or SDK needs a stable contract under balance at $0.002 per successful item; validation failures never consume balance after the engine rejects the request. Puzzle sites can precompute answers for display and reveal them on demand with the same endpoint. Authors shipping SDKs can map the result field straight into a copy button while method and letters_mirrored make OpenAPI examples self-explanatory. Keep payloads to ordinary text sizes appropriate for a Worker isolate item call; this tool is for messages and snippets, not multi-megabyte binary blobs.