Twilio API · SMS · Two-Factor Auth · UK
Twilio SMS API Integration.
Automated SMS notifications, appointment reminders, two-factor authentication and two-way messaging built directly into your platform using the Twilio API. Straightforward to integrate, quick to deploy, immediately effective. Fixed price. You own the code.
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What it does
What Twilio SMS integration provides.
Twilio is the most widely used SMS API platform. It delivers SMS messages to any UK or international number, receives inbound replies via webhooks, and provides Twilio Verify for SMS-based two-factor authentication and phone number verification.
SMS open rates are above 90% — significantly higher than email. A custom Twilio integration triggers messages from events in your system: order confirmed, appointment scheduled, payment failed, user registered. Messages are personalised with dynamic content from your database and delivered within seconds. For appointment-based businesses, the two-way confirmation flow — customer replies YES or NO — converts silent no-shows into advance notice cancellations without any manual effort.
Who it’s for
Who uses a Twilio SMS integration.
Healthcare, dental and medical practices
Appointment reminders sent automatically 24 hours and 2 hours before each appointment. Patients reply YES to confirm or NO to cancel. Confirmation status written back to the booking system. No manual reminder calls, no missed appointments that weren’t flagged in advance. For private practices, a single no-show is often worth more in recovered revenue than the integration costs to build.
Beauty, wellness and trades businesses
Hair salons, beauty therapists, personal trainers, boiler engineers, pest control — any appointment-based service business where a no-show is a lost slot that can’t be recovered. The reminder and reply-to-cancel flow gives enough notice to fill cancelled slots. The ROI is direct and measurable: fewer empty appointments, more revenue per working day.
Ecommerce businesses on WooCommerce
Order confirmations, despatch alerts and delivery notifications sent by SMS rather than (or alongside) email. SMS open rates far exceed email for transactional messages — customers actually see that their order has shipped. Failed payment recovery SMS prompts customers to complete checkout with a higher response rate than email. Post-delivery review requests via SMS get more clicks than email equivalents.
Platforms needing two-factor authentication
SMS OTP for registration, login or high-value transaction confirmation using Twilio Verify. Verify handles code generation, rate limiting, brute-force protection and voice fallback out of the box — more secure than building OTP logic from scratch and simpler to implement correctly. For platforms holding financial, health or personal data where account security matters.
Service businesses with payment follow-up
SMS notifications triggered by Stripe or GoCardless payment events — payment confirmed, payment failed, subscription renewal due. A payment failure SMS with a direct link to retry gets significantly higher response rates than a payment failure email. For subscription businesses where failed payment recovery directly affects monthly revenue, automating the recovery sequence is worth the build cost many times over.
Why custom
Why a plugin won’t cut it.
WooCommerce SMS plugins and off-the-shelf SMS platforms handle basic scenarios. Custom trigger logic, personalised message content and two-way reply handling require a bespoke build.
Any trigger, any event
Plugins fire on standard order status changes. A custom integration fires on any event in your system — booking created, payment failed, stock depleted, custom field updated — with any conditional logic you need.
Two-way reply handling
Plugins only send. A custom integration handles inbound replies — YES/NO confirmations, keyword triggers, STOP opt-out — and writes the result back to your system automatically.
UK registration included
UK A2P sender registration is required for reliable delivery on UK networks. It’s handled as part of the build — not something you’re left to figure out separately.
No ongoing platform fees
Off-the-shelf SMS platforms charge monthly fees on top of messaging costs. A custom integration is a one-time build cost. You pay Twilio directly for messages only.
The process
How a Twilio SMS integration is built.
Scoped quickly, built efficiently, tested thoroughly. SMS integrations are fast to deploy compared to more complex API builds.
Scoping
We map your trigger events, message content, whether replies need handling and whether Twilio Verify is required. Most scoping conversations take 30 minutes.
Fixed-price quote
Clear, itemised quote before work begins. Scope agreed in writing.
Twilio setup and UK registration
Twilio account configuration, UK phone number or sender ID provisioning, UK A2P sender registration submitted and webhook endpoints configured.
Build and integration
Trigger logic, message templates with dynamic content, inbound webhook handler and any Verify flow built and integrated with your platform.
Testing and handover
Tested across real UK mobile networks with a range of message content and edge cases. Complete documentation. You own the code.
The deliverable
What’s included.
What I build
- Twilio API authentication and secure credential handling
- Outbound SMS trigger logic from your events
- Dynamic message content from your database
- UK A2P sender registration (submitted and managed)
- UK phone number or alphanumeric sender ID setup
- Delivery status callbacks and failure logging
- Inbound SMS webhook handler (if in scope)
- Keyword recognition — YES/NO/STOP and custom keywords
- Twilio Verify OTP flow (if in scope)
- STOP opt-out handling and customer opt-out storage
- Technical handover document
What’s not included
- Twilio account setup — free at twilio.com, takes minutes
- Ongoing Twilio messaging costs — ~4–5p per UK SMS, billed by Twilio
- UK number rental — ~£1–2/month, charged by Twilio
- SMS message copywriting — message templates agreed with you, written by you
- Voice and IVR flows — separate tier, quoted individually
- Changes to your platform outside the integration scope
Pricing
Fixed-price builds. No hidden costs.
SMS integration is one of the fastest builds in the range. Ongoing Twilio messaging costs (around 4–5p per UK SMS) are paid directly to Twilio — not marked up.
SMS Notifications
£595
~3–5 days
Automated one-way SMS triggered by events in your platform. Personalised message content from your database, UK sender setup and A2P registration, delivery status callbacks and error handling. For appointment reminders, order notifications, payment alerts and any event-driven outbound SMS.
- Outbound SMS trigger logic
- Dynamic message content
- UK sender ID or number setup
- UK A2P registration
- Delivery callbacks and error logging
- STOP opt-out handling
- Inbound reply handling
- Twilio Verify 2FA
Two-way + Verify
£1,195
~1 week
Everything in SMS Notifications, plus inbound reply handling for two-way conversations (YES/NO confirmations, keyword responses, cancellation flows) and Twilio Verify for SMS OTP and phone verification. For appointment businesses needing confirmations, and platforms requiring two-factor authentication.
- Everything in SMS Notifications
- Inbound SMS webhook handler
- Keyword recognition and reply routing
- Confirmation status write-back to your system
- Twilio Verify — start and check verification
- Rate limiting and brute-force protection
Voice & IVR
£1,995
~2 weeks
Automated outbound voice calls and inbound call routing with IVR menus. Appointment reminders delivered by voice call, automated payment chasing calls, inbound routing to the right team. A different audience from SMS — voice builds take longer and require careful call flow scripting.
- Outbound voice call automation
- TwiML call flow scripting
- Inbound call routing
- IVR menu configuration
- Voice fallback for SMS failures
- Technical handover document
Payment terms: 50% on agreement, balance on completion before handover. You’ll need a Twilio account (free to register at twilio.com) and a UK phone number or approved sender ID.
Common questions
Twilio SMS API FAQ.
Does Twilio SMS work reliably on UK networks?
Yes — Twilio has direct carrier connections with major UK networks. The key requirement for reliable delivery is completing UK A2P (Application to Person) sender registration, which is included in every build. Without registration, messages may be filtered by some UK carriers. With it, delivery rates are consistently high.
Can my business name appear as the sender instead of a phone number?
Yes — alphanumeric sender IDs let your business name appear as the sender (e.g. “AcmePlumbing”). This is one-way only; customers can’t reply. For two-way conversations where replies are needed, a UK long number is used instead. The right setup depends on whether you need replies — confirmed during scoping.
How much does Twilio SMS cost per message?
UK outbound SMS is approximately 4–5p per message, billed by Twilio directly. A UK phone number rental is around £1–2/month. Twilio Verify (for 2FA) is approximately 5p per verification attempt. These are Twilio’s own charges — not marked up as part of the build cost.
What is Twilio Verify and why is it better than building my own OTP?
Twilio Verify is a purpose-built product for SMS and voice OTP verification. It handles code generation (cryptographically secure), code expiry, rate limiting on requests, and brute-force protection after failed attempts — all things that need to be implemented correctly in a DIY approach. Using Verify is more secure, simpler and maintainable than rolling your own OTP logic.
Can customers opt out of SMS messages?
Yes — and they must be able to. Customers who reply STOP are automatically opted out by Twilio and no further messages are sent to their number. The integration records opt-out status against the customer record to prevent future send attempts. STOP handling is included in every build.
What platforms can it integrate with?
Any platform with server-side code. WooCommerce, custom PHP, Laravel, Python, Node.js, bespoke booking systems. The integration hooks into whatever events your platform fires — there’s no dependency on a specific platform type.
How quickly can it be deployed?
The SMS Notifications tier typically takes 3–5 days from kick-off to go-live. The main variable is UK A2P registration approval timing, which is outside our control but is submitted at the start of the build. Development happens in parallel, so registration approval rarely holds up the timeline.
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Need Twilio SMS integration built?
Tell me what events should trigger messages and what the messages should say — I’ll come back with a clear answer on what’s involved and what it costs. Most SMS projects are scoped in a single conversation.
