Why the opt-out line changes your segment count
Opt-out language is what turns a marketing text into a compliant one, and most guidance stops at "add STOP instructions" without saying what that costs. It's rarely free: a base message sitting at 155 GSM-7 characters is one segment, and a 25-character footer pushes the same message to two, because GSM-7 segments cap at 160 characters for a single message and 153 once a message has to be split (concatenated) across segments. The literal keyword stays STOP in every language here, since that's what gateways and carriers actually parse, but a few of the surrounding native sentences use characters (Polish zrezygnować, Czech odhlášení, Turkish yazıp) that sit outside the GSM-7 default alphabet and force UCS-2 encoding, dropping the per-segment budget to 70 characters (67 once split) regardless of message length.
None of that is a reason to skip the footer — it's a reason to see the real number before you ship copy to a list. Pick your languages, paste the message it's attached to, and this shows the before/after segment count and an example cost delta at $0.0125 per segment (the US per-message rate; other destinations run cheaper, down to a $0.004 floor). Everything runs in the browser against the same GSM-7/UCS-2 logic used by the deliverability linter.