Why are Twitter messages 140 characters?

Did I post this already? I don’t think I did. Hopefully not.

Why are Twitter messages 140 characters?

Because they were designed to fit into the 160 characters of a text message, with some characters filled up with header information and so on.

So why are text messages 160 characters?

Because they fit into 140 bytes, or 160 7-bit characters.

That, in turn, was so the messages could fit into unused space within the signalling formats used by phone networks.

By Daniel Bowen

Transport blogger / campaigner and spokesperson for the Public Transport Users Association / professional geek.
Bunurong land, Melbourne, Australia.
Opinions on this blog are all mine.

7 replies on “Why are Twitter messages 140 characters?”

Which leads, in turn, to the next question: Why are SMS messages 27.5 cents each (or $2 million per gigabyte) if they’re just sent in a bit of unused transmission space? Surely the mechanism for farming messages out to the correct recipients can’t cost that much to run.

Wouldn’t a better explanation be that Twitter messages are limited to 140 characters, because 140 **8-bit** characters take up 140 bytes??

@Philip: I will never understand people who still use SMS for that very reason. The cheapest SMS rate floating around (that I know of) is LiveConnected, whose text message rate is $0.006 (assuming you use up all $500 of the “M” cap (i.e. send 2000 texts in a month), which costs $11.99 a month), which would equate to $42,857 per GB. That’s assuming all of your text messages are filled with 160 characters (that being the “best case scenario”).
Yet 1GB of mobile data these days barely costs $10. And with smartphones having apps which let you send messages through the data network, I fail to see why there are still smartphone users using SMS (to contact other smartphone users).

@Ronnie Maybe because there are instances where the message can be delayed due to server issues (Apple’s iMessage is horrible)

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