SMS essentials

An SMS looks simple, but two rules decide how long it can be and how many SMS a single send really costs: how many characters fit in one message, and what happens when you go over. Knowing them is what keeps your messages short, on-brand and easy to budget. In short: stick to the basic character set and each message counts as a single SMS.

Length and encoding

A standard SMS holds up to 160 characters. That "standard" is the GSM-7 character set: the Latin letters A–Z and a–z, the digits 0–9 and common punctuation — what you type most of the time.

The moment you add a character outside that set — an accent (á, ñ), an emoji, or a non-Latin alphabet — the message switches to Unicode encoding and the limit drops straight to 70 characters.

Encoding	When it's used	Characters per SMS
Standard (GSM-7)	Latin letters, digits, common punctuation	160
Unicode	Accents, emojis, non-Latin scripts	70 (67 per part when split across several SMS)

When a message counts as more than one SMS

If your text goes over the limit, it isn't cut off: it's split into several SMS and sent together, so your contact still reads it as one message. The difference shows up on the bill, because each part counts as one SMS: a 200-character standard message is two SMS, and a message that tips into Unicode (say, one emoji) can become two as well. With Unicode the per-SMS limit also tightens when the message splits: a single Unicode SMS holds 70 characters, but 67 per part once it spans more than one SMS, because each part carries the data needed to reassemble them. Knowing this lets you keep most messages to a single SMS and your costs predictable.

Avoiding accidental Unicode

Sometimes a single accent or emoji is enough to halve your limit without you noticing. When that happens, the editor flags it with a banner — This message contains unicode characters — explaining that Unicode caps each SMS at 70 characters instead of 160.

If the Unicode wasn't intentional, use Remove unicode characters to swap them for their plain equivalents automatically (Á → A, ó → o). Your message goes back to the 160-character standard limit.

How your sender appears abroad

In some countries carriers replace an alphanumeric sender with a number before delivering the message. When that happens your contact sees a number instead of your brand name, and can't tell the SMS is from you. The usual fix is to name your brand in the message text — in international campaigns you sometimes need to and sometimes don't, depending on the destination.

To handle this without editing every message, set a Brand prefix on the sender. It's a short text Instasent prepends to the message automatically, and only in the countries that replace the alphanumeric sender — so your brand stays visible there without showing twice where the sender already carries it. It's a field on the sender itself, configured once in the sender's settings, not something you add to the body each time.

Which countries replace the sender is a regulatory matter, covered in Countries & regulation; senders (and the brand prefix field) are managed in SMS senders & registration.

Messages in several languages

A campaign can carry several language versions of the same SMS; each contact gets the version that matches their language, and everyone else gets the default. You set this up while writing the campaign — see Creating a campaign.