> ## Documentation Index
> Fetch the complete documentation index at: https://docs.tied.com/llms.txt
> Use this file to discover all available pages before exploring further.
# SMS and MMS
> Universal reach, real compliance obligations, and the encoding detail that surprises people on their first invoice.
SMS reaches every phone ever made. No app, no smartphone, no data connection. It is also the most heavily regulated channel Tied supports, and the one where a naive implementation produces a bill several times larger than expected.
Both of those are worth understanding before you send anything.
## Four kinds of number
| Type | Throughput | Registration | Best for |
| - | - | - | - |
| **10DLC** | Standard | Brand + campaign registration required | Most business messaging |
| **Toll-free** | Higher | Verification, no campaign registration | Faster onboarding, higher volume |
| **Short code** | Highest | Carrier vetting | High-volume marketing, OTP, alerts |
| **Vanity** | — | — | A memorable, easy-to-recall number |
10DLC is where most accounts land. Toll-free is the pragmatic choice when you need throughput sooner than campaign registration allows. Short codes are a commitment — see the rental costs in [SMS channel fees](/pricing/channel-fees/sms-mms).
## Registration is not optional
**10DLC registration is mandatory for all US long-code A2P traffic.** Unregistered traffic is filtered
or blocked by carriers — not delayed, blocked. There is no grace period to send through.
Registration runs through The Campaign Registry and is passed through at cost. You register a **brand** once, then a **campaign** per use case — support, marketing, notifications are separate campaigns with separate approvals.
Budget days, not hours. Brand vetting and campaign vetting each add time.
## Compliance you are responsible for
SMS is governed by TCPA and CTIA rules in the US, and equivalents elsewhere. These obligations are **yours**, and most of the enforcement happens at the carrier rather than in Tied:
Consent must be specific to the kind of message you will send. Consent to order updates is not
consent to marketing.
STOP, UNSUBSCRIBE, CANCEL, END and QUIT must all unsubscribe, and the confirmation must go out
straight away.
**On US 10DLC and toll-free numbers the carrier enforces this at the network level** — it
intercepts the keyword and stops delivery before the message reaches you. Tied does not
inspect inbound message content for opt-out keywords, so do not rely on Tied to maintain your
suppression list. Keep your own, and reconcile it with the carrier's.
HELP must return your business name and a way to reach a human. Same division: the carrier
handles the standard keyword response, and anything beyond that is yours to build — an
[automation rule](/automation) matching the message content is the usual way.
If a complaint escalates, you need to show when and how consent was given.
## Segments and encoding — the billing surprise
This is the detail that catches people.
SMS bills **per segment**, and a segment is:
* **Up to 160 GSM-7 characters** in one segment, or **153 per segment** when the message is longer
* **Up to 70 Unicode characters** in one segment, or **67 per segment** when the message is longer
An emoji or curly quote can move the entire message into Unicode. Some GSM-7 symbols, including braces, brackets and the euro sign, count as two characters. An emoji counts as two Unicode characters. Accented letters in the GSM alphabet do not force Unicode. A 140-character message that fits in one GSM segment becomes **three** Unicode segments when it contains a character that switches it to Unicode.
**An emoji can add one or more billable segments.** If you are
templating outbound SMS at volume, strip or standardise punctuation. Curly quotes from a word
processor are the single most common cause of unexpectedly doubled segment counts.
Every segment is billed, including the final segment when it is only partly filled.
## MMS
MMS bills **per message** regardless of size, up to 5MB. Images, GIFs and audio. Because it is per-message rather than per-segment, a long caption costs no more than a short one — the opposite of SMS.
## SMS as RCS fallback
If you run [RCS](/channels/rcs), Tied falls back to SMS automatically when a recipient's device or carrier cannot receive RCS. You are billed only for the message that actually delivers.
This is the main reason to register SMS even if RCS is your intended channel — without it, a fallback has nowhere to go.
## Rates
Per-segment and per-message rates across all four US carriers, plus number rental and registration fees, are published in full: [SMS, MMS and short code fees](/pricing/channel-fees/sms-mms).
## Next
Per-carrier rates, number rental and 10DLC registration costs.
The richer channel that falls back to this one.
Sending to a segment, and the opt-in rules that apply.
How SMS compares to everything else.
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