Researchers reverse-engineer iPhone keyboard's hidden blocklist: ~100K phrases across 28 languages

sethlazar · x · 2026-11-08

Researchers found Apple's iOS keyboard doesn't store a plaintext blocklist; instead it embeds a compiled minimal perfect hash table of 32-bit word fingerprints inside the keyboard's language-model files.
When swipe-typing or using autocomplete, the keyboard converts input to token IDs, evaluates 2–6 word n-grams, and hashes them with Bob Jenkins's public-domain hashword(). A table match means the predictor refuses the suggestion, or the swipe model actively redirects to an alternate word.
On Nov 6, researcher Derik Kauffman released Swipeblocked, enumerating candidate combinations to recover the hidden phrases — conservatively 100,000 entries across 28 languages. The English list includes conspiracy-adjacent phrases like "NSA surveillance," "left wing conspiracy," and "Covid was a hoax," with each entry also covering word-form variants ("sleepy Joe" also blocks "sleepier Joe").

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