What TextFlow SMS API does and who it's for
TextFlow SMS API is a REST-based messaging API built around a single premise: route outbound SMS through hardware you already own — a phone or SIM-equipped device — rather than through a cloud carrier pool. That distinction shapes everything about when this API makes sense and when it does not.
For developers building internal tools, small-scale notification systems, or lightweight OTP flows where controlling the sending number and avoiding per-message carrier fees matters more than managed infrastructure, TextFlow is worth a serious look. Its 9.9 popularity score and nearly 4,000 marketplace subscribers suggest a real user base, and a recorded 100% success rate alongside a 69 ms average latency puts it in the same performance bracket as well-established providers.
TextFlow is now part of the TextLink product family. The API documentation lives at docs.textlinksms.com and there is a no-code Bulk SMS interface at textlinksms.com for teams that want to send batches without writing any code.
Endpoint walkthrough
The API surface is intentionally minimal — four POST endpoints covering two distinct workflows.
Service health
POST /service/check — Before sending a message, you can ping this endpoint to verify that the service is reachable and measure current response time. Useful in monitoring scripts or as a pre-flight check before batch sends. The BASIC plan treats calls to this endpoint as unlimited, so it does not count against your monthly request budget in any meaningful throttling sense.
SMS sending
POST /send-sms — The core endpoint. The request body accepts a phone_number (with country code, which the docs explicitly flag as required) and a text field. The API returns a response indicating send status. Because the actual transmission happens through your own device, the latency figure of 69 ms represents the API's own processing time; end-to-end message delivery is governed by your carrier and device connectivity.
OTP verification flow
The two remaining endpoints form a complete two-step phone verification system:
POST /send-code — Triggers a 6-digit OTP to the specified phone number. You do not generate or store the code yourself; TextFlow handles that.
POST /verify-code — Accepts the code your user enters alongside their phone_number. The API confirms whether the code is valid, completing the verification loop. Calls to the verify-code endpoint are classed as "Check code" requests, which the BASIC plan allows on an unlimited basis.
This pair gives you a ready-to-deploy phone verification system without needing a separate identity or verification service, as long as you have a device connected to TextFlow.
Pricing
TextFlow currently offers a single documented pricing tier:
| Plan | Monthly cost | SMS/OTP requests | Service checks | Code checks |
|---|---|---|---|---|
| BASIC | $0 | 100,000 / month | Unlimited | Unlimited |
The 100,000 monthly request ceiling applies to the send-sms and send-code calls. For the majority of small-to-medium applications — transactional alerts, user onboarding verification, internal notifications — this ceiling is generous. At 100k messages per month you are looking at roughly 3,300 messages per day, which covers a substantial number of active users for non-high-volume use cases.
Because the plan is free with no trial period caveat mentioned in the available data, you can integrate and operate indefinitely without a billing relationship. That said, if your volume ever exceeds 100k requests per month, you should consult the provider's site for higher-tier options not currently listed here.
Practical use cases
Phone number verification at signup — The send-code / verify-code pair maps directly onto a standard registration flow. Instead of wiring up Twilio Verify or a similar paid service, you call two endpoints and let TextFlow manage the OTP lifecycle.
Internal operational alerts — Teams that need to push SMS notifications to on-call staff or field personnel can do so from a known, company-owned SIM, which keeps the sender number stable and avoids shared-pool number rotation.
Low-volume transactional messaging — Order confirmations, appointment reminders, or shipping updates for businesses that send a few thousand messages per month fit comfortably within the free plan's 100k ceiling.
No-code bulk sends — Non-technical users on your team can access the Bulk SMS tool at textlinksms.com directly, without any API integration. This is useful for marketing or operations teams running one-off campaigns.
Third-party workflow automation — The API works with Make.com, Zapier, and GoHighLevel (GHL), meaning you can trigger SMS sends from workflow automation tools without writing custom integration code.
Limitations and things to check before integrating
Device dependency is the primary constraint. Unlike Twilio, Vonage, or similar providers, TextFlow does not supply carrier infrastructure. Your messages go out through a physical device you control, which means uptime is contingent on that device staying connected, charged, and registered on a network. This is a meaningful operational burden for production systems that need guaranteed delivery windows.
Country code is mandatory on phone_number. The documentation flags this explicitly — omitting it will cause send failures. Validate user input to include the leading country code before hitting the API.
No inbound SMS endpoint is listed. The four documented endpoints cover outbound sending and verification only. If your application needs to receive replies or handle two-way conversations, evaluate whether the platform supports that separately.
Single pricing tier visible. The BASIC plan at $0 is the only plan documented here. If your application grows past 100k monthly sends, check the provider's site for current upgrade paths.
Getting started
The provider offers a tutorial video at the URL in the description — a good first stop if you prefer a visual walkthrough. The full reference documentation is at docs.textlinksms.com. For a typical integration path:
- Create an account at textlinksms.com.
- Connect a device (the TextLink app on a phone with an active SIM is the standard setup).
- Grab your API credentials from the dashboard.
- Test reachability with POST /service/check before writing any business logic.
- Implement the send-sms call with a hardcoded test number, confirming the response shape matches your error-handling assumptions.
- Layer in the send-code / verify-code pair if you need phone verification.
Given the 100% recorded success rate and sub-70 ms API latency, the integration experience is likely to be smooth once the device side is configured correctly. The device-dependency question is the one to resolve early in your evaluation — if your infrastructure team can guarantee device uptime, most of the other concerns are minor.
