The SMS API with compliance built in

Send transactional texts with one API call. Textmux files the toll-free verification paperwork, vets every sender, and handles STOP and HELP in the send path itself. You write code; the carrier requirements are our job.

Get early access Early access. US toll-free messaging first.

# One call to get a token. No forms.
$ curl -X POST https://api.textmux.com/v1/accounts
{ "token": "tmx_...", "balance": 0 }

# One call to send.
$ curl https://api.textmux.com/v1/messages \
    -H "Authorization: Bearer tmx_..." \
    -d '{ "to": "+12065550142", "text": "Your order shipped." }'
{ "status": "queued", "segments": 1 }

How it works

Three calls to production

Create an account

One POST returns a bearer token. Add an email if you want a dashboard; skip it if you do not.
Register your sender

Tell us who is texting and how recipients opted in. We review it, register it with carriers, and file the verification paperwork for you. Approvals and rejections always come with reasons.
Send

You can send while verification is in review. Messages route through our verified pool, then cut over to your own number automatically on approval. The industry's slowest onboarding step becomes a non-event.

Your number is yours

Dedicated numbers are registered to your business identity, and you can port your number out any time. No lock-in by hostage-taking.

Billing that matches carriers

Real GSM-7 and UCS-2 segment math, so you are billed for exactly what carriers transmit. Failed deliveries are refunded automatically.

Two-way out of the box

Inbound replies and delivery events arrive on your webhook, signed. STOP and START are processed before they ever reach you.

For agents

An SMS API a machine can buy

Textmux is agent-native by design, with the same vetting rules as everyone else.

No signup flow

Accounts are created by API call and authenticated by bearer token. No email, no dashboard, no CAPTCHA between an agent and its first message.

Pay inline with x402

Out of credits? The send returns HTTP 402 with an exact quote. Retry the same call with payment attached and the message goes out. One round trip.

Machine-readable everything

Docs, pricing, and errors are all structured JSON. Idempotency keys on every write. An agent can integrate without reading a single web page.

Messaging policy

Consent is the rule

Every message sent through Textmux goes to someone who asked for it. That policy is what keeps delivery rates high for everyone on the platform, so it applies to every sender, on every plan, with no exceptions.

Opt-in, verified up front

Sender applications describe how recipients opt in, and we review them before the first message. Transactional messages and opted-in notifications only.

No cold outreach.
No purchased, rented, or scraped lists.
No carrier-prohibited content categories (including sex, hate, alcohol, firearms, tobacco, cannabis, and gambling).

STOP and HELP, automatic

Recipients can reply STOP to any message to opt out instantly. Opt-outs are enforced in the send path: suppressed sends are reported to you and never delivered, never charged. START opts back in. HELP returns sender identity and support contact.

The no-silent-suspension promise

If your account needs enforcement action, you will always know why. Warnings come with the specific reason and a window to fix it. Rejections carry reasons. Appeals are answered by humans.

Pricing

Flat and per-segment

One price per segment.

Carrier fees included, verification paperwork included, no monthly minimum. Pay as you go with card or x402. Published rates land here at launch; early access partners get them first.