Why only 160? The truth behind the SMS character limit

Text message marketing is an important, effective tool to increase customer engagement and a company's bottom line. But the technology behind it, SMS, has a strict 160 character limit, which has remained unchanged even as technology has advanced. Why is that?

Although text messaging gained popularity in the late 1990s, the format was invented in the 1980s. According to the Los Angeles Times, one of the originators of SMS, Friedhlem Hillebrand, settled on the 160 character limit based on a typewriter, as one line of text on a typewriter has 160 characters.

At the time, mobile technology was limited as to the amount of data that could be transmitted and received efficiently and with consistency. Limiting the number of characters per message was important to achieve success with SMS while working within the technological constraints.

But that was almost 30 years ago. Why hasn't the limit increased? The reason comes down to infrastructure. 

One of the things that makes SMS unique is that any cell phone can receive them. They are not reliant on mobile data. According to WiseGeek, carriers use a special channel when transmitting text messages that was specifically created for the format. The infrastructure that supports networks, including towers and other cell sites, have hardware restrictions that impose the SMS character limit to ensure that both text and voice are transmitted effectively.

As mentioned earlier, the SMS protocol supports up to 160 ASCII characters (standard alpha/numeric characters), but some telecom companies put a further cap on messages, only allowing up to 135 characters. Though some modern phone software can re-assemble messages over the character limit, a best practice is to stay within the lower 135 character limit. This will ensure that messages are concise and efficient, as well as universal across all devices. While many cell phone plans are now unlimited, staying within the limit will help save people money if they don't have unlimited service and lead to less confusion over messages being split up two more times and potentially being received out of order.

As mobile technology advances and fragments, SMS remains the one constant in the field, offering quick, reliable communication between devices. And that's due, in part, to its character limit.