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SMS marketing has an open rate of over 98%. It’s an immediate, personal, and devastatingly effective way to reach your customers. But this power comes with significant responsibility. In the United States, a single non-compliant text message can trigger lawsuits and fines of $500 to $1,500 per message under the Telephone Consumer Protection Act (TCPA).
Your entire compliance strategy starts with a single, simple concept: the SMS opt-in keyword.
This is the very first interaction a customer has with your brand over text. Getting it right is non-negotiable. It’s the digital handshake that secures “express written consent” and protects your business from massive legal risk.
But what makes an SMS opt-in keyword compliant? It’s not just the word itself—it’s the entire ecosystem around it. This ultimate guide will walk you through the non-negotiable rules of US compliance, provide 15 real-world examples you can use today, and explain the difference between a high-performing keyword and a costly mistake.
🏛️ What Exactly Are SMS Opt-in Keywords?
In the simplest terms, an SMS opt-in keyword is a specific word or phrase that a consumer texts to a phone number (often a 5- or 6-digit short code) to subscribe to a text messaging program.
When a user texts “DEALS” to 12345, “DEALS” is the keyword.
This action triggers an automated workflow. It’s the digital equivalent of a user raising their hand and saying, “Yes, I want you to text me.” This action is the key to proving consent.
However, US regulations (primarily from the TCPA and the CTIA) state that just texting a keyword is not enough. That keyword must be presented with a clear and conspicuous “call-to-action” (CTA) that explains exactly what the user is signing up for.
⚖️ The Two Pillars of US Compliance: TCPA & CTIA
Before we get to the examples, you must understand the rules. In the US, compliance isn’t just a good idea; it’s a legal and operational mandate.
1. The TCPA (Telephone Consumer Protection Act)
This is the federal law governing all telemarketing. For SMS marketing, its most important mandate is “prior express written consent.”
What it means: You must have a clear, documented record of a specific individual agreeing to receive promotional text messages from you.
**How SMS opt-in keywords help: A text-in keyword, when combined with a compliant CTA, is a valid form of express written consent. The user is taking a clear, affirmative action to subscribe.
The Risk: Fines of $500-$1,500 per violation. This is why you cannot, under any circumstances, buy a list of phone numbers and start texting them.
2. The CTIA (Cellular Telecommunications Industry Association)
The CTIA is not a law, but it’s the association for the mobile carriers themselves (like T-Mobile, Verizon, and AT&T). If you violate their guidelines, the carriers can—and will—shut down your short code or number, effectively ending your SMS program.
The CTIA’s guidelines are all about transparency. They demand that any CTA promoting an SMS opt-in keyword must include the following disclosures:
Program Description: What is the user signing up for? (e.g., “for special offers and alerts”)
Message Frequency: How often will you text? (e.g., “Msg frequency varies,” “Up to 5 msgs/week”)
Msg & Data Rates: The magic phrase: “Message and data rates may apply.”
HELP/STOP Commands: How to get help and how to opt out. (e.g., “Text HELP for help, STOP to cancel.”)
Links to T&Cs/Privacy: A direct link to your Terms & Conditions and Privacy Policy.
This is the anatomy of compliance. The keyword is the trigger, but the disclosures are the legal armor.
✅ The Anatomy of a 100% Compliant Call-to-Action (CTA)
You cannot just put “Text JOIN to 12345!” on a poster. You must include the disclosures.
Here is a template you can follow.
Bad Example (Non-Compliant): Text VIP to 12345 for our deals!
This is a TCPA lawsuit waiting to happen. It has no disclosures, no consent language, and no way for the user to know what they’re really agreeing to.
Good Example (Fully Compliant): “Text DEALS to 12345 to join our VIP club & get 20% off. Msg frequency varies. Msg&data rates may apply. Text HELP for help, STOP to unsubscribe. View Terms [link] & Privacy [link].”
Let’s break down why this works:
Clear Keyword: “DEALS”
Clear Short Code: “12345”
Clear Offer: “get 20% off”
Program Description: “join our VIP club”
All CTIA Disclosures: Frequency, Msg Rates, and HELP/STOP commands are all present.
This entire block of text must be present anywhere you advertise your SMS opt-in keyword—on your website, in an email, on a physical sign, or in a social media ad. This is a foundational part of any successful pay-per-click (PPC) marketing campaign that drives SMS signups.
15 Essential SMS Opt-in Keyword Examples (Categorized)
The keyword itself should be simple, relevant, and easy to type. Avoid long words or words that auto-correct can easily mangle.
Here are 15 compliant SMS opt-in keywords categorized by their strategic purpose.
Category 1: The “High Intent” Classics
These are straightforward, unambiguous, and perfect for general-purpose list building. They show clear intent to subscribe.
JOIN: The most popular and direct keyword. It’s simple, clear, and universally understood.
START: Similar to “JOIN,” this keyword implies the beginning of a relationship. It’s clean and affirmative.
SUBSCRIBE: While slightly longer, this is the most legally unambiguous keyword. There is no doubt what the user intended to do.
OPTIN: A bit more industry jargon, but very clear for legal purposes.
YES: Often used in a “double opt-in” flow (more on that later) or as a simple confirmation on a web form.
Category 2: The “Value-Driven” Keywords
These keywords work best when tied to a specific, immediate reward. They are perfect for retail, e-commerce, and restaurants.
DEALS: Promises immediate value. The user knows they are signing up to save money.
VIP: Makes the user feel special. This is great for loyalty clubs or exclusive access.
SAVE: A powerful, action-oriented keyword. “Text SAVE to 12345 to get 25% off.”
CLUB: Similar to VIP, this builds a sense of community and exclusivity.
ACCESS: Perfect for “early access” to sales, ticket drops, or content.
Category 3: The “Informational” Keywords
These are for programs that are less about promotions and more about providing timely information.
ALERTS: Ideal for service-based businesses, finance, or logistics. (e.g., “Text ALERTS to 12345 for shipping updates.”)
UPDATE: A great keyword for news, community information, or B2B communications.
NEWS: Perfect for media organizations, blogs, or local news outlets.
INFO: A simple, all-purpose keyword for general information requests that lead to a subscription.
Category 4: The “Brand-Specific” Keyword
[YOURBRAND]: Using your brand name (e.g., “Text ‘NIKE’ to 12345”) is a powerful way to build brand identity. It’s also a great way to ensure you’re not competing with other businesses on a generic keyword.
🔒 Single vs. Double Opt-In: The Ultimate Compliance Shield
Now that you have your SMS opt-in keyword, you must decide on your subscription workflow.
Single Opt-In: The user texts your keyword. They immediately receive one confirmation message (that also includes the compliance disclosures) and are officially subscribed. It’s fast and has less friction.
Double Opt-In: The user texts your keyword. They receive an initial message asking them to confirm.
Flow:
User: “JOIN”
System: “Reply Y to confirm you want to receive recurring marketing texts from [Your Brand]. Msg&data rates may apply. …”
User: “Y”
System: “Welcome! You are now subscribed…”
Which one is better?
From a strict E-E-A-T and legal compliance perspective, double opt-in is infinitely superior.
It is the gold standard for proving “express written consent.” In a legal dispute, you have an undeniable, two-step record of the user’s intent. It also builds a much higher-quality list by filtering out mistyped numbers, spam bots, and low-intent users. This is a best practice we recommend to all our web design and development clients when building consent forms.
❌ 5 Critical Mistakes to Avoid with Your SMS Opt-in Strategy
Forgetting the Disclosures: This is the #1 mistake. Advertising your SMS opt-in keyword without the full CTIA disclosures (Msg&data rates, freq, HELP/STOP) makes your entire program non-compliant.
Using Confusing Keywords: Don’t use “DEALS4U” or “SAVE!20.” Keep it to a single, simple, alphabetic word. Autocorrect is not your friend.
Not Honoring STOP: Your SMS platform must automatically recognize and honor “STOP,” “QUIT,” “CANCEL,” “END,” and “UNSUBSCRIBE.” This must be immediate and global (opting them out of all lists).
No Confirmation Message: After a user texts your keyword, you must send an immediate confirmation reply. This message must, once again, include the compliance disclosures and HELP/STOP commands.
Assuming Consent from Other Forms: A user giving you their phone number on a “Contact Us” form is not consent to receive marketing texts. You must have a separate, unticked checkbox specifically for SMS marketing (with all the disclosures) to be compliant.
FAQs: Mastering the "Open Now" Filter
Q1: What are the best SMS opt-in keywords?
The best keywords are short, simple, and relevant to your offer. “JOIN,” “DEALS,” “VIP,” and “SAVE” are the most effective and popular because they are easy to remember, easy to type, and clearly state the user’s intent.
Q2: Can I use multiple SMS opt-in keywords?
Yes! In fact, you should. You can use different keywords for different campaigns to track their effectiveness. For example, use “DEALS” on your website pop-up and “SAVE” on your in-store signage. This allows you to see which channel drives more subscribers.
Q3: What is the difference between a short code, a 10DLC, and a Toll-Free Number?
A Short Code (e.g., 12345) is a 5-6 digit number designed for high-volume mass texting. It’s the most professional but also the most expensive. A 10DLC (10-Digit Long Code) is a regular 10-digit local phone number approved for A2P (Application-to-Person) texting. It’s the new standard for most businesses. A Toll-Free Number (e.g., 800-XXX-XXXX) can also be text-enabled for business messaging. All three must follow the same TCPA/CTIA rules.
Q4: How do I get an SMS opt-in keyword?
You don’t “get” the keyword itself; you get it through your SMS marketing platform (like Twilio, Attentive, Postscript, etc.). When you provision a short code or 10DLC, you can configure your platform to listen for specific SMS opt-in keywords and trigger the automated reply.
Q5: What is the TCPA "safe harbor"?
The TCPA “safe harbor” refers to a defense a company might have if they accidentally text a number that has been reassigned to a new user without their knowledge. To qualify, you generally must prove you checked the number against the Reassigned Numbers Database (RND) within a certain timeframe. This is an advanced topic, but it highlights why maintaining a clean, consent-based list is so critical.