> ## Documentation Index
> Fetch the complete documentation index at: https://docs.apollodeploy.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Signal SDKs

> Install an official Apollo Signal SDK and send from your language or framework

Apollo Signal publishes public SDKs from the same API contract. Each SDK defaults to
`https://api.signal.apollodeploy.com` and exposes the same email, contact, domain, metrics,
suppression, and webhook operations.

<Note>
  Use SDKs only in trusted server, worker, or command-line environments. Never include a Signal API
  key in browser JavaScript, a mobile binary, or a public repository.
</Note>

## Before you install

1. [Create an API key](/signal/create-an-api-key) with **Emails: Send** permission.
2. [Add and verify a sending domain](/signal/add-a-domain).
3. Store the key as `SIGNAL_API_KEY` in your server-side secret manager.

## JavaScript and TypeScript

| Runtime | Package                     | Install                                 | Guide                                          |
| ------- | --------------------------- | --------------------------------------- | ---------------------------------------------- |
| Node.js | `@apollo-deploy/signal-sdk` | `npm install @apollo-deploy/signal-sdk` | [Node.js](/signal/send-with/send-with-nodejs)  |
| Next.js | `@apollo-deploy/signal-sdk` | `npm install @apollo-deploy/signal-sdk` | [Next.js](/signal/send-with/send-with-nextjs)  |
| Express | `@apollo-deploy/signal-sdk` | `npm install @apollo-deploy/signal-sdk` | [Express](/signal/send-with/send-with-express) |

## Languages and frameworks

| Language or framework | Package                                                  | Install                                                         | Guide                                          |
| --------------------- | -------------------------------------------------------- | --------------------------------------------------------------- | ---------------------------------------------- |
| Python                | `apollo-deploy-signal-sdk`                               | `pip install apollo-deploy-signal-sdk`                          | [Python](/signal/send-with/send-with-python)   |
| Go                    | `github.com/apollo-deploy/signal-sdks/sdks/go/signal/v4` | `go get github.com/apollo-deploy/signal-sdks/sdks/go/signal/v4` | [Go](/signal/send-with/send-with-go)           |
| Ruby                  | `apollo-deploy-signal-sdk`                               | `gem install apollo-deploy-signal-sdk`                          | [Ruby](/signal/send-with/send-with-ruby)       |
| Rails                 | `apollo-deploy-signal-sdk-rails`                         | `gem install apollo-deploy-signal-sdk-rails`                    | [Rails](/signal/send-with/send-with-rails)     |
| PHP                   | `apollo-deploy/signal-sdk`                               | `composer require apollo-deploy/signal-sdk`                     | [PHP](/signal/send-with/send-with-php)         |
| Laravel               | `apollo-deploy/signal-sdk`                               | `composer require apollo-deploy/signal-sdk`                     | [Laravel](/signal/send-with/send-with-laravel) |
| Java                  | `com.apollodeploy.signal:signal-sdk-java`                | Version `4.0.1` from Maven Central                              | [Java](/signal/send-with/send-with-java)       |
| Kotlin                | `com.apollodeploy.signal:signal-sdk-kotlin`              | Version `4.0.1` from Maven Central                              | [Kotlin](/signal/send-with/send-with-kotlin)   |
| .NET                  | `ApolloDeploy.Signal`                                    | `dotnet add package ApolloDeploy.Signal`                        | [.NET](/signal/send-with/send-with-dotnet)     |
| Rust                  | `apollo-signal-sdk`                                      | `cargo add apollo-signal-sdk`                                   | [Rust](/signal/send-with/send-with-rust)       |
| Elixir                | `apollo_signal`                                          | `{:apollo_signal, "~> 4.0"}`                                    | [Elixir](/signal/send-with/send-with-elixir)   |
| Swift                 | `ApolloSignal`                                           | Swift Package Manager from `Apollo-Deploy/signal-sdks`          | [Swift](/signal/send-with/send-with-swift)     |
| Zig                   | `apollo_signal`                                          | Public release archive for Zig 0.16.0                           | [Zig](/signal/send-with/send-with-zig)         |

PHP and Laravel intentionally use one Composer package. Laravel discovers the bundled service
provider automatically; plain PHP applications load only the core SDK.

## Public source and downloads

All SDK source, checksummed release archives, and generation provenance are public in
[Apollo-Deploy/signal-sdks](https://github.com/Apollo-Deploy/signal-sdks). The Signal API
implementation remains private.

The command-line package is also available as `@apollo-deploy/signal-cli`:

```bash theme={"dark"}
npm install --global @apollo-deploy/signal-cli
```

<Card title="SDK examples" icon="code" href="/signal/send-with/sdk-examples">
  Copy production send examples for every published SDK, including HTML, metadata, idempotency,
  and test mode.
</Card>

## After the API accepts a message

A successful send returns an ID for the accepted message. Acceptance is not final delivery. Open
**Emails** to follow the timeline, or configure signed webhooks for asynchronous delivery, bounce,
complaint, rejection, and suppression outcomes.

<CardGroup cols={2}>
  <Card title="REST API" icon="brackets-curly" href="/signal/send-with/send-with-rest">
    Call the public HTTP API without an SDK.
  </Card>

  <Card title="SMTP" icon="envelope" href="/signal/send-with/send-with-smtp">
    Send through a standard SMTP client.
  </Card>
</CardGroup>