Two-way SMS keyword & auto-reply designer.
Design the inbound-keyword rules for a two-way SMS number — STOP, HELP, START and your own custom keywords — then type a message into the simulator and see exactly which auto-reply fires. Everything runs in your browser; nothing is sent.
A design & preview tool — it does not send real messages.
This tool does not provision a live number or send/receive real SMS. It helps you design and rehearse your keyword logic. STOP and HELP guidance here is best-practice, not legal advice. To run this on a real two-way number, talk to BroadNet.
Keyword rules
Each rule maps one or more inbound keywords to an auto-reply. Rules are evaluated top to bottom — the first match wins, so keep the most specific rules highest. Keyword matching is case-insensitive.
- 1Usually mandatory
The whole inbound message equals the keyword.
104 charsGSM-71 seg - 2Usually mandatory
The whole inbound message equals the keyword.
91 charsGSM-71 seg - 3
The whole inbound message equals the keyword.
78 charsGSM-71 seg - 4
The inbound message begins with the keyword.
65 charsGSM-71 seg
Sent when an inbound message matches no rule. Leave empty to send nothing (silent).
Conversation simulator
Type an inbound message as if a subscriber texted your number. The tool matches it against your rules (respecting match type and order) and shows the auto-reply.
Send an inbound message to see the auto-reply.
Checks & warnings
- No issues found. STOP and HELP rules are present and replies fit one segment.
Export rule set
Copy the whole design as JSON to share with your team or hand to BroadNet when provisioning a real number.
The short answer
What is a two-way SMS keyword auto-reply?
A keyword auto-reply is an inbound rule on a two-way SMS number: when a subscriber texts a defined keyword, the platform sends back a pre-written message automatically. The universal compliance keywords are STOP (opt out), HELP (get assistance) and START (opt back in), but you can define any custom keyword — like BALANCE, HOURS or a promo word — to route or answer messages without a human in the loop.
How matching and precedence work
Each rule carries one or more keywords and a match type: exact (the whole message equals the keyword), starts-with (the message begins with it) or contains (the keyword appears anywhere). Incoming text is normalised — trimmed and lower-cased — then tested against your rules from top to bottom. The first rule that matches wins and its auto-reply is sent; nothing below it is evaluated. If no rule matches, the configurable fallback reply is used. Order matters: put exact opt-out and help rules above broad contains-rules so a message like “STOP the promo” still opts the user out.
Why STOP and HELP are mandatory
For application-to-person (A2P) and two-way programs, mobile operators and messaging aggregators generally require that STOP (and its synonyms UNSUBSCRIBE, CANCEL, END, QUIT) reliably opt a subscriber out and return a confirmation, and that HELP (or INFO) returns program information and a contact. Many networks honour these keywords at the carrier level regardless of your app logic, so your auto-replies should confirm the action rather than contradict it. This tool flags a missing STOP or HELP rule, but final requirements depend on your country, number type and aggregator — confirm with BroadNet before launch.
Frequently asked questions
Does this tool send or receive real SMS?
No. It is a design and preview tool that runs entirely in your browser. It does not provision a number and never sends or receives a real message. The simulator only mimics how your rules would respond. To run keyword auto-replies on a live two-way number, contact BroadNet.
Which keywords are mandatory?
For compliant A2P and two-way programs, STOP (opt-out) and HELP (assistance) are almost always required, and their synonyms — UNSUBSCRIBE, CANCEL, END, QUIT for opt-out; INFO for help — are commonly expected too. START (or SUBSCRIBE, UNSTOP) lets an opted-out user opt back in. Exact requirements vary by country, number type and aggregator.
What is the difference between exact, starts-with and contains?
Exact fires only when the whole inbound message equals the keyword (after trimming and lower-casing) — best for STOP and HELP. Starts-with fires when the message begins with the keyword, useful for commands like “BALANCE 12345”. Contains fires when the keyword appears anywhere, which is the loosest and should sit lowest in your rule order to avoid catching messages you didn't intend.
Why does rule order matter?
Rules are evaluated top to bottom and the first match wins. A broad contains-rule placed above your STOP rule could swallow an opt-out message. Keep exact, high-priority rules like STOP and HELP at the top and looser contains-rules at the bottom.
Can auto-replies use variables?
Yes. You can write placeholders like {{brand}} or {{code}} in a reply. This tool leaves them in place in the preview because it has no live data; on a real BroadNet two-way number those variables are filled from your message payload or subscriber profile.
Why should replies stay within one segment?
An SMS holds 160 characters in GSM-7 or 70 in Unicode before it splits into multiple billed segments. Auto-replies fire on every matching inbound message, so a multi-segment reply multiplies cost at scale. This tool shows the encoding and segment count per reply and warns when one exceeds a single segment.
Ready to run this on a real number?
BroadNet's Two-Way SMS gives you inbound webhooks, keyword routing and virtual long codes, short codes and 10DLC numbers. Bring your rule set and we'll help you launch a compliant conversational flow.