--- title: Unicode's Transliteration Rules Are Turing-Complete description: UTS #35 transliteration rules, the rewrite-rule format used in Unicode locale data and shipped in ICU (used by most OSes, browsers, and databases), are... canonical: https://daily.dev/posts/unicode-s-transliteration-rules-are-turing-complete-r39lucn1n twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Unicode's Transliteration Rules Are Turing-Complete | daily.dev og:description: UTS #35 transliteration rules, the rewrite-rule format used in Unicode locale data and shipped in ICU (used by most OSes, browsers, and databases), are... og:url: https://daily.dev/posts/unicode-s-transliteration-rules-are-turing-complete-r39lucn1n og:image: https://api.daily.dev/og/posts/r39luCN1N.png og:image:alt: Unicode's Transliteration Rules Are Turing-Complete og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Unicode's Transliteration Rules Are Turing-Complete **[Hacker News](https://daily.dev/sources/hn)** · 6 min read · 0 upvotes · 0 comments ## Summary UTS #35 transliteration rules, the rewrite-rule format used in Unicode locale data and shipped in ICU (used by most OSes, browsers, and databases), are Turing-complete under their natural unbounded semantics. The proof compiles a 2-tag system — a known universal model of computation — into three transliteration rules, then demonstrates it computing the Collatz function step by step using PyICU and ICU's uconv tool. Additional examples implement Rule 110 cellular automaton and a prime-generating automaton entirely in rule files. ICU adds a pragmatic loop limit (16 rewrites per code point) to prevent infinite loops, but the spec itself defines no bound. The practical implication: accepting transform rule files from untrusted sources is equivalent to accepting arbitrary code execution. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Unicode 18.0.0](https://daily.dev/posts/unicode-18-0-0-szoqqkwii) · Lobsters · 0 upvotes · 0 comments - [Full Unicode Search at 50× ICU Speed with AVX‑512](https://daily.dev/posts/full-unicode-search-at-50-icu-speed-with-avx-512-s9bwdg8zf) · Hacker News · 0 upvotes · 0 comments - [Parsing Taiwanese Like Code](https://daily.dev/posts/parsing-taiwanese-like-code-cf3ktfvls) · Ruby Flow · 1 upvotes · 0 comments - [Your iPhone Keyboard Is Running 1948 Math](https://daily.dev/posts/your-iphone-keyboard-is-running-1948-math-xvczgqxfa) · Medium · 0 upvotes · 0 comments --- Tags: [#security](https://daily.dev/tags/security) [View this post on daily.dev](https://daily.dev/posts/unicode-s-transliteration-rules-are-turing-complete-r39lucn1n) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Unicode's Transliteration Rules Are Turing-Complete","url":"https://daily.dev/posts/unicode-s-transliteration-rules-are-turing-complete-r39lucn1n","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/unicode-s-transliteration-rules-are-turing-complete-r39lucn1n"},"datePublished":"2026-07-09T07:49:58.651Z","dateModified":"2026-07-09T07:53:28.368Z","description":"UTS #35 transliteration rules, the rewrite-rule format used in Unicode locale data and shipped in ICU (used by most OSes, browsers, and databases), are...","image":"https://media.daily.dev/image/upload/s--2-1xRawN--/f_auto/v1722860399/public/Placeholder%2011","thumbnailUrl":"https://media.daily.dev/image/upload/s--2-1xRawN--/f_auto/v1722860399/public/Placeholder%2011","isAccessibleForFree":true,"articleSection":"Hacker News","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Hacker News","logo":"https://media.daily.dev/image/upload/t_logo,f_auto/v1/logos/hn","url":"https://daily.dev/sources/hn"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/unicode-s-transliteration-rules-are-turing-complete-r39lucn1n","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"security","timeRequired":"PT6M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Hacker News","item":"https://daily.dev/sources/hn"},{"@type":"ListItem","position":3,"name":"Unicode's Transliteration Rules Are Turing-Complete"}]} ```