Why a Text Message Is 160 Characters
An engineer typed postcards on his typewriter until he ran out of room. That became the SMS limit.
In 1985, a German communications researcher named Friedhelm Hillebrand sat at a typewriter in his home in Bonn and banged out sentences. Postcards, random thoughts, questions he might ask a colleague. Most of them, he noticed, came in under 160 characters.
He was looking for a number. GSM, the European digital-mobile standard then under design, had a spare slice of the signaling channel — 140 bytes per second — that could carry short text alongside voice calls. Hillebrand needed a character limit that fit in that slot and still felt like a real message. His typewriter experiment said 160.
The committee argued. A rival proposal wanted 128 characters; some wanted more. Hillebrand's number won, partly because he could show it with pages of real sentences. GSM shipped in 1992 with 160-character SMS, using a 7-bit alphabet to cram 160 letters into those 140 bytes.
The cap outlived its constraint. By the time smartphones arrived, the signaling channel's size no longer mattered — but 160 had become the shape of a text. When Twitter launched in 2006, it picked 140 characters so a tweet plus a 20-character username would still fit in one SMS.
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