SMS & MMS

Messaging

Integrate powerful, programmable, high-throughput SMS and MMS with SignalWire APIs, SDKs, and no-code application builders

View as Markdown

Programmable Messaging is deeply integrated in the SignalWire platform. Our robust APIs, SDKs, and application builders are backed by first-class support and a team dedicated to compliance and class-leading delivery rates across all carriers and locations.

SignalWire is your Messaging partner from proof-of-concept to deployment. Get up and running quickly with our Getting Started guides and get registration right the first time with our comprehensive Guide to The Campaign Registry (TCR).

Try it out

1version: 1.0.0
2sections:
3  main:
4    - send_sms:
5        from_number: "+155512312345"
6        to_number: "+15555554321"
7        body: "Hello from SignalWire!"
1version: 1.0.0
2sections:
3  main:
4    - send_sms:
5        from_number: "+155512312345"
6        to_number: "+15555554321"
7        media: ["https://mcdn.signalwire.com/images/v2/loud/LogoLarge.jpg"]
1import { SignalWire } from "@signalwire/realtime-api";
2
3const client = await SignalWire({ project: "ProjectID Here", token: "Token Here"})
4
5await client.messaging.listen({
6  topics: ["office"],
7  async onMessageReceived(message) {
8    client.messaging.send({
9        to: message.from,
10        from: message.to,
11        body: `The message ${message.body} has been received!`
12    })
13  }
14})
1import { SignalWire } from "@signalwire/realtime-api";
2
3const client = await SignalWire({ project: "ProjectID Here", token: "Token Here"})
4
5await client.messaging.listen({
6  topics: ["office"],
7  async onMessageReceived(message) {
8    client.messaging.send({
9        to: "+1xxxxxxxxxx",
10        from: message.to,
11        body: `
12        You received a message from ${message.from} to SignalWire number ${message.to}.
13        The message was: ${message.body}
14        `
15    })
16  }
17})

Choose an API

SignalWire’s many API offerings make it quick and easy to send and receive SMS and MMS within an application through a variety of phone number types. There are a few different ways to utilize these services, so we encourage you to browse the documentation for our APIs.

Looking for Chat or PubSub?

SignalWire’s Messaging APIs are tailored for SMS and MMS over the PSTN. For non-PSTN applications, check out our Chat APIs.

REST APIs

Use classic HTTP calls to manage brands and campaigns, configure phone numbers, and much more.

Reference

Character limits

How message segments are measured and priced.

MIME types

Supported media types for MMS.

Frequently asked questions

  1. Create a Brand.
  2. Register a Campaign.
  3. Assign phone numbers to the campaign.

Full details are explained in our Registration guide.

As of December 2025, newly purchased US 10DLC numbers do not have messaging capabilities enabled by default.

To enable messaging:

  • Outbound/mixed use: Assign your number to an approved TCR campaign. Messaging is automatically enabled once the number is assigned.
  • Inbound-only use: Contact Support to request inbound messaging enablement.
  • Testing only: Your first purchased number is automatically enabled for Platform Free Trial when paired with a verified mobile number.

10DLC is a type of phone number. Short for 10 Digit Local Code, it is a type of phone number that includes an area code followed by 7 additional digits indicating a specific channel. For example, +12345678910, where the “+1” indicates the country, the “234” indicates the area code, and the remaining digits indicate the channel.

Toll-free numbers, although slightly more expensive, allow for increased throughput out-of-the-box. They also have a registration process tied to them, however once complete, have a higher deliverability rating than traditional 10DLC numbers.

The Campaign Registry is a platform that was created in partnership with a company called Kaleyra and several Mobile Network Operators (MNOs). The platform itself acts as a source of information about every 10DLC number being used for outbound SMS through A2P routes in an effort to discourage spam in the industry. In short, any and all 10DLC numbers that are to be used for SMS in SignalWire’s platform must be registered through the Campaign Registry. You can find more information about the Campaign Registry in-depth here.

Yes! You can do this through the SignalWire REST APIs. Check out the documentation.

The number of messages you can send out depends on a few different factors. If you are using a toll-free number, there is no real limit outside of throughput in regards to the amount of messages you could feasibly send. With 10DLC, it depends on your registered use case with the Campaign Registry. AT&T provides a limit on the amount of texts per minute you can send to an end-user at the campaign level whereas T-Mobile limits the overall amount of SMS per day you can send to and end user at the brand level. For more information around this, consult our guide to The Campaign Registry.

There is some content that is explicitly disallowed from being sent via SMS/MMS with SignalWire. You can see this list in full detail here.

Carrier Passthrough Fees, also known as Network Access Fees (NAFs), are additional fees that Mobile Network Operators (MNOs), or Carriers, charge on a per-SMS/MMS basis for the ability of that SMS/MMS to be passed-through their network.

No. Every carrier (MNO) assesses their own rates for inbound and outbound SMS.

For verified toll-free numbers, you can contact sales at sales@signalwire.com to increase the throughput of those numbers up to 100 MPS for an additional price.

SignalWire does not provide a way to explicitly send to Verizon end-users or end-users of any other MNO.

You can verify toll-free traffic by opening a support ticket with us. Our team will follow up with the forms and information we need from you within that support ticket.

No. Customers are responsible for handling inbound stop requests and removing those customers from subscriber lists. Messages should not go out to these numbers again unless they have opted back in via an Unstop request.

Carriers consider anything more than 5% opt-out to be a high rate for consumers who have opted in and therefore should want to receive these messages.

Not currently. We have no way to turn off inbound SMS at this time. You can leave your numbers unset up for messaging and nothing will happen when inbound messages come into the numbers though!

We do not have a “scheduled” queue, but messages that exceed your throughput will be entered into your Space’s backlog and sent when possible. Read about the backlog and queue system here! The default message backlog is 10,000 for the entire Space. These limits can be increased based on the use case and individual approval following an account verification request.

Messages are charged when they are ‘Sent’ successfully - meaning they leave our network without issue. They are charged regardless of whether or not they deliver after they have left our network. You are not charged while your messages are queued or ‘failed’ (failed meaning they never left our network).

Visit our error code explanation page for details.