Signal CLI REST API (bbernhard/signal-cli-rest-api)

Signal CLI REST API

https://github.com/bbernhard/signal-cli-rest-api
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A Dockerized REST API for Signal Messenger, providing functionalities like sending messages,...

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# Signal CLI REST API

Signal CLI REST API is a Dockerized REST API wrapper around signal-cli, enabling programmatic access to Signal Messenger functionality. The project provides a complete HTTP interface for sending and receiving Signal messages, managing contacts and groups, handling attachments, and controlling device registration—all without requiring the official Signal mobile app for day-to-day operations.

Built with Go and the Gin web framework, the API supports three execution modes: normal (standard JVM-based signal-cli), native (GraalVM-compiled binary for faster startup), and json-rpc (persistent daemon for maximum performance). The service exposes comprehensive endpoints for message operations, group management, profile updates, device linking, typing indicators, reactions, receipts, and more. It's designed for integration into home automation systems, notification services, chatbots, and custom Signal-based applications.

## API Endpoints

### Register Phone Number

Register a new phone number with the Signal network, optionally using voice verification or captcha.

```bash
# SMS verification (default)
curl -X POST -H "Content-Type: application/json" \
  'http://localhost:8080/v1/register/+431212131491291'

# Voice verification
curl -X POST -H "Content-Type: application/json" \
  --data '{"use_voice": true}' \
  'http://localhost:8080/v1/register/+431212131491291'

# With captcha (required when Signal requests it)
# 1. Visit https://signalcaptchas.org/registration/generate.html
# 2. Extract captcha value from browser console
# 3. Use in registration:
curl -X POST -H "Content-Type: application/json" \
  -d '{"captcha":"signalcaptcha://03AGdBq24QSFj..."}' \
  'http://localhost:8080/v1/register/+431212131491291'
```

### Verify Phone Number

Verify a registered phone number using the SMS/voice verification code.

```bash
curl -X POST -H "Content-Type: application/json" \
  'http://localhost:8080/v1/register/+431212131491291/verify/123-456'

# With PIN (if account uses Signal PIN)
curl -X POST -H "Content-Type: application/json" \
  --data '{"pin": "1234"}' \
  'http://localhost:8080/v1/register/+431212131491291/verify/123-456'
```

### Unregister Phone Number

Unregister a phone number from Signal, optionally deleting the account and local data.

```bash
# Unregister without deleting account or local data
curl -X POST -H "Content-Type: application/json" \
  'http://localhost:8080/v1/unregister/+431212131491291'

# Unregister and delete account from Signal servers
curl -X POST -H "Content-Type: application/json" \
  -d '{"delete_account": true}' \
  'http://localhost:8080/v1/unregister/+431212131491291'

# Unregister, delete account, and delete local data
curl -X POST -H "Content-Type: application/json" \
  -d '{"delete_account": true, "delete_local_data": true}' \
  'http://localhost:8080/v1/unregister/+431212131491291'
```

### Link Device via QR Code

Link the API instance as a secondary device by scanning a QR code with your primary Signal app.

```bash
# Generate QR code (open in browser or use curl to get PNG)
curl -X GET 'http://localhost:8080/v1/qrcodelink?device_name=signal-api'

# Or with wget to save QR code image
wget -O qrcode.png 'http://localhost:8080/v1/qrcodelink?device_name=HomeAssistant'

# Then: Open Signal app → Settings → Linked devices → + → Scan QR code
```

### Send Message (v2)

Send a text message with optional attachments, mentions, quotes, stickers, and formatting.

```bash
# Simple text message
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "message": "Hello from Signal API!",
    "number": "+431212131491291",
    "recipients": ["+4354546464654", "+4912812812121"]
  }' \
  'http://localhost:8080/v2/send'

# Response: {"timestamp":"1697123456789"}

# Message with base64 attachment
ATTACHMENT=$(base64 -w 0 image.jpg)
curl -X POST -H "Content-Type: application/json" \
  -d "{
    \"message\": \"Check this out!\",
    \"number\": \"+431212131491291\",
    \"recipients\": [\"+4354546464654\"],
    \"base64_attachments\": [\"${ATTACHMENT}\"]
  }" \
  'http://localhost:8080/v2/send'

# Styled text message (bold, italic, strikethrough)
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "message": "*bold text* _italic text_ ~strikethrough~ ||spoiler|| `monospace`",
    "number": "+431212131491291",
    "recipients": ["+4354546464654"],
    "text_mode": "styled"
  }' \
  'http://localhost:8080/v2/send'

# Message with mentions
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "message": "Hey @John, check this out!",
    "number": "+431212131491291",
    "recipients": ["+4354546464654"],
    "mentions": [
      {"author": "+4354546464654", "start": 4, "length": 5}
    ]
  }' \
  'http://localhost:8080/v2/send'

# Quote/reply to message
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "message": "I agree!",
    "number": "+431212131491291",
    "recipients": ["+4354546464654"],
    "quote_timestamp": 1697123456789,
    "quote_author": "+4354546464654",
    "quote_message": "Original message text"
  }' \
  'http://localhost:8080/v2/send'

# Send to group (get group_id from /v1/groups/{number})
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "message": "Hello group!",
    "number": "+431212131491291",
    "recipients": ["group.ckRzaEd4VmRzNnJaASAEsasa"]
  }' \
  'http://localhost:8080/v2/send'

# Link preview
THUMB=$(base64 -w 0 thumbnail.png)
curl -X POST -H "Content-Type: application/json" \
  -d "{
    \"message\": \"Check out https://www.example.com\",
    \"number\": \"+431212131491291\",
    \"recipients\": [\"+4354546464654\"],
    \"link_preview\": {
      \"url\": \"https://www.example.com\",
      \"title\": \"Example Site\",
      \"description\": \"An example website\",
      \"base64_thumbnail\": \"${THUMB}\"
    }
  }" \
  'http://localhost:8080/v2/send'

# View-once image
curl -X POST -H "Content-Type: application/json" \
  -d "{
    \"message\": \"Self-destructing image\",
    \"number\": \"+431212131491291\",
    \"recipients\": [\"+4354546464654\"],
    \"base64_attachments\": [\"${ATTACHMENT}\"],
    \"view_once\": true
  }" \
  'http://localhost:8080/v2/send'

# Edit a previously sent message
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "message": "Updated message text",
    "number": "+431212131491291",
    "recipients": ["+4354546464654"],
    "edit_timestamp": 1697123456789
  }' \
  'http://localhost:8080/v2/send'
```

### Receive Messages

Subscribe to incoming messages via WebSocket connection for real-time message reception.

```bash
# Using curl (limited WebSocket support)
curl -X GET 'http://localhost:8080/v1/receive/+431212131491291'

# Using wscat (recommended for WebSocket)
wscat -c ws://localhost:8080/v1/receive/+431212131491291

# Python example for message reception
import websocket
import json

def on_message(ws, message):
    data = json.loads(message)
    print(f"From: {data['envelope']['source']}")
    print(f"Message: {data['envelope']['dataMessage']['message']}")
    if 'attachments' in data['envelope']['dataMessage']:
        for att in data['envelope']['dataMessage']['attachments']:
            print(f"Attachment: {att['id']}")

ws = websocket.WebSocketApp(
    "ws://localhost:8080/v1/receive/+431212131491291",
    on_message=on_message
)
ws.run_forever()
```

### Create Group

Create a new Signal group with specified members and settings.

```bash
# Basic group
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "name": "My Project Team",
    "members": ["+4354546464654", "+4912812812121"]
  }' \
  'http://localhost:8080/v1/groups/+431212131491291'

# Response: {"id":"group.ckRzaEd4VmRzNnJaASAEsasa"}

# Group with description and permissions
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "name": "Family Group",
    "description": "Our family chat",
    "members": ["+4354546464654", "+4912812812121", "+4976543210987"],
    "permissions": {
      "add_members": "only-admins",
      "edit_group": "only-admins",
      "send_messages": "every-member"
    },
    "group_link": "enabled-with-approval",
    "expiration_time": 86400
  }' \
  'http://localhost:8080/v1/groups/+431212131491291'
```

### List Groups

Retrieve all groups for a registered number.

```bash
# List all groups
curl -X GET -H "Content-Type: application/json" \
  'http://localhost:8080/v1/groups/+431212131491291'

# Response example:
# [
#   {
#     "id": "group.ckRzaEd4VmRzNnJaASAEsasa",
#     "internal_id": "abc123...",
#     "name": "Family Group",
#     "description": "Our family chat",
#     "members": ["+4354546464654", "+4912812812121"],
#     "admins": ["+431212131491291"],
#     "blocked": false,
#     "pending_invites": [],
#     "pending_requests": [],
#     "invite_link": "https://signal.group/..."
#   }
# ]

# Get specific group details
curl -X GET -H "Content-Type: application/json" \
  'http://localhost:8080/v1/groups/+431212131491291/group.ckRzaEd4VmRzNnJaASAEsasa'
```

### Update Group

Modify group settings, members, or admins.

```bash
# Update group name and description
curl -X PUT -H "Content-Type: application/json" \
  -d '{
    "name": "Updated Group Name",
    "description": "New description"
  }' \
  'http://localhost:8080/v1/groups/+431212131491291/group.ckRzaEd4VmRzNnJaASAEsasa'

# Add members
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "members": ["+4988877766655"]
  }' \
  'http://localhost:8080/v1/groups/+431212131491291/group.ckRzaEd4VmRzNnJaASAEsasa/members'

# Remove members
curl -X DELETE -H "Content-Type: application/json" \
  -d '{
    "members": ["+4988877766655"]
  }' \
  'http://localhost:8080/v1/groups/+431212131491291/group.ckRzaEd4VmRzNnJaASAEsasa/members'

# Add admins
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "admins": ["+4354546464654"]
  }' \
  'http://localhost:8080/v1/groups/+431212131491291/group.ckRzaEd4VmRzNnJaASAEsasa/admins'

# Update avatar
AVATAR=$(base64 -w 0 group_avatar.jpg)
curl -X PUT -H "Content-Type: application/json" \
  -d "{
    \"base64_avatar\": \"${AVATAR}\"
  }" \
  'http://localhost:8080/v1/groups/+431212131491291/group.ckRzaEd4VmRzNnJaASAEsasa'
```

### Delete Group

Delete a Signal group permanently.

```bash
curl -X DELETE -H "Content-Type: application/json" \
  'http://localhost:8080/v1/groups/+431212131491291/group.ckRzaEd4VmRzNnJaASAEsasa'
```

### Block Group

Block a Signal group to stop receiving messages from it.

```bash
curl -X POST -H "Content-Type: application/json" \
  'http://localhost:8080/v1/groups/+431212131491291/group.ckRzaEd4VmRzNnJaASAEsasa/block'
```

### Join Group

Join a Signal group using an invite link.

```bash
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "group_link": "https://signal.group/#..."
  }' \
  'http://localhost:8080/v1/groups/+431212131491291/group.ckRzaEd4VmRzNnJaASAEsasa/join'
```

### Quit Group

Leave a Signal group without deleting it.

```bash
curl -X POST -H "Content-Type: application/json" \
  'http://localhost:8080/v1/groups/+431212131491291/group.ckRzaEd4VmRzNnJaASAEsasa/quit'
```

### Get Group Avatar

Retrieve the avatar image for a specific group.

```bash
curl -X GET 'http://localhost:8080/v1/groups/+431212131491291/group.ckRzaEd4VmRzNnJaASAEsasa/avatar' \
  --output group_avatar.jpg
```

### Send Reaction

React to a message with an emoji.

```bash
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "recipient": "+4354546464654",
    "reaction": "👍",
    "target_author": "+4354546464654",
    "timestamp": 1697123456789
  }' \
  'http://localhost:8080/v1/reactions/+431212131491291'

# Remove reaction
curl -X DELETE -H "Content-Type: application/json" \
  -d '{
    "recipient": "+4354546464654",
    "reaction": "",
    "target_author": "+4354546464654",
    "timestamp": 1697123456789
  }' \
  'http://localhost:8080/v1/reactions/+431212131491291'
```

### Send Receipt

Send read or viewed receipt for a message.

```bash
# Send read receipt
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "recipient": "+4354546464654",
    "receipt_type": "read",
    "timestamp": 1697123456789
  }' \
  'http://localhost:8080/v1/receipts/+431212131491291'

# Send viewed receipt (for view-once messages)
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "recipient": "+4354546464654",
    "receipt_type": "viewed",
    "timestamp": 1697123456789
  }' \
  'http://localhost:8080/v1/receipts/+431212131491291'
```

### Typing Indicator

Show or hide typing indicator to a recipient.

```bash
# Start typing indicator
curl -X PUT -H "Content-Type: application/json" \
  -d '{
    "recipient": "+4354546464654"
  }' \
  'http://localhost:8080/v1/typing-indicator/+431212131491291'

# Stop typing indicator
curl -X DELETE -H "Content-Type: application/json" \
  -d '{
    "recipient": "+4354546464654"
  }' \
  'http://localhost:8080/v1/typing-indicator/+431212131491291'
```

### Update Profile

Update your Signal profile name, avatar, and about text.

```bash
# Update name only
curl -X PUT -H "Content-Type: application/json" \
  -d '{
    "name": "John Doe"
  }' \
  'http://localhost:8080/v1/profiles/+431212131491291'

# Update with avatar and about
AVATAR=$(base64 -w 0 profile_pic.jpg)
curl -X PUT -H "Content-Type: application/json" \
  -d "{
    \"name\": \"John Doe\",
    \"base64_avatar\": \"${AVATAR}\",
    \"about\": \"Signal user since 2024\"
  }" \
  'http://localhost:8080/v1/profiles/+431212131491291'
```

### Manage Contacts

List, update, and sync contacts.

```bash
# List all contacts
curl -X GET 'http://localhost:8080/v1/contacts/+431212131491291'

# Response example:
# [
#   {
#     "number": "+4354546464654",
#     "uuid": "abc-123-def-456",
#     "name": "John Smith",
#     "profile_name": "John",
#     "color": "blue",
#     "blocked": false,
#     "message_expiration": "0",
#     "profile": {
#       "given_name": "John",
#       "about": "Engineer",
#       "has_avatar": true
#     }
#   }
# ]

# Update contact
curl -X PUT -H "Content-Type: application/json" \
  -d '{
    "recipient": "+4354546464654",
#     "name": "John Smith",
    "expiration_in_seconds": 86400
  }' \
  'http://localhost:8080/v1/contacts/+431212131491291'

# Sync contacts to linked devices
curl -X POST 'http://localhost:8080/v1/contacts/+431212131491291/sync'

# Get specific contact by UUID
curl -X GET 'http://localhost:8080/v1/contacts/+431212131491291/abc-123-def-456'

# Get contact avatar
curl -X GET 'http://localhost:8080/v1/contacts/+431212131491291/abc-123-def-456/avatar' \
  --output contact_avatar.jpg
```

### Search Phone Numbers

Check if phone numbers are registered with Signal.

```bash
# Single number
curl -X GET 'http://localhost:8080/v1/search/+431212131491291?numbers=%2B4354546464654'

# Multiple numbers (URL-encoded)
curl -X GET 'http://localhost:8080/v1/search/+431212131491291?numbers=%2B4354546464654,%2B4912812812121'

# Response:
# [
#   {"number": "+4354546464654", "registered": true},
#   {"number": "+4912812812121", "registered": false}
# ]
```

### Manage Attachments

List, serve, and delete attachments.

```bash
# List all stored attachments
curl -X GET 'http://localhost:8080/v1/attachments'

# Response: ["attachment_id_1", "attachment_id_2"]

# Download attachment
curl -X GET 'http://localhost:8080/v1/attachments/attachment_id_1' \
  --output downloaded_file.jpg

# Delete attachment
curl -X DELETE 'http://localhost:8080/v1/attachments/attachment_id_1'
```

### Trust Identity

Trust a contact's safety number for enhanced security.

```bash
# Trust with safety number verification
curl -X PUT -H "Content-Type: application/json" \
  -d '{
    "verified_safety_number": "12345 67890 12345 67890 12345 67890"
  }' \
  'http://localhost:8080/v1/identities/+431212131491291/trust/+4354546464654'

# Trust all known keys
curl -X PUT -H "Content-Type: application/json" \
  -d '{
    "trust_all_known_keys": true
  }' \
  'http://localhost:8080/v1/identities/+431212131491291/trust/+4354546464654'

# List identities
curl -X GET 'http://localhost:8080/v1/identities/+431212131491291'
```

### List Registered Accounts

List all registered and linked accounts on this API instance.

```bash
curl -X GET 'http://localhost:8080/v1/accounts'

# Response example:
# ["+431212131491291", "+441234567890"]
```

### Manage Devices

List and add linked devices to your Signal account.

```bash
# List linked devices
curl -X GET 'http://localhost:8080/v1/devices/+431212131491291'

# Response example:
# {
#   "devices": [
#     {
#       "id": 1,
#       "name": "signal-api",
#       "created": 1697123456789,
#       "last_seen": 1697234567890
#     }
#   ]
# }

# Add a new device by URI (from another device's QR code)
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "uri": "sgnl://linkdevice?uuid=..."
  }' \
  'http://localhost:8080/v1/devices/+431212131491291'
```

### Account Management

Set username, manage PIN, update account settings.

```bash
# Set username
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "username": "johndoe.42"
  }' \
  'http://localhost:8080/v1/accounts/+431212131491291/username'

# Response: {"username": "johndoe.42", "username_link": "https://signal.me/#..."}

# Remove username
curl -X DELETE 'http://localhost:8080/v1/accounts/+431212131491291/username'

# Set Signal PIN
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "pin": "123456"
  }' \
  'http://localhost:8080/v1/accounts/+431212131491291/pin'

# Remove PIN
curl -X DELETE 'http://localhost:8080/v1/accounts/+431212131491291/pin'

# Update account settings
curl -X PUT -H "Content-Type: application/json" \
  -d '{
    "discoverable_by_number": true,
    "share_number": false
  }' \
  'http://localhost:8080/v1/accounts/+431212131491291/settings'
```

### Rate Limit Challenge

Solve captcha to lift rate limit restrictions.

```bash
# When you receive 429 error with challenge_tokens, solve captcha:
# 1. Visit https://signalcaptchas.org/challenge/generate.html
# 2. Get captcha value from console
# 3. Submit with challenge token:

curl -X POST -H "Content-Type: application/json" \
  -d '{
    "challenge_token": "token_from_error_response",
    "captcha": "signalcaptcha://03AGdBq24..."
  }' \
  'http://localhost:8080/v1/accounts/+431212131491291/rate-limit-challenge'
```

### Sticker Packs

List and add sticker packs.

```bash
# List installed sticker packs
curl -X GET 'http://localhost:8080/v1/sticker-packs/+431212131491291'

# Add sticker pack (get pack_id and pack_key from https://signalstickers.org)
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "pack_id": "9a32eda01a7a28574f2eb48668ae0dc4",
    "pack_key": "19546e18eba0ff69dea78eb591465289d39e16f35e58389ae779d4f9455aff3a"
  }' \
  'http://localhost:8080/v1/sticker-packs/+431212131491291'

# Send message with sticker (use pack_id:sticker_id format)
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "number": "+431212131491291",
    "recipients": ["+4354546464654"],
    "sticker": "9a32eda01a7a28574f2eb48668ae0dc4:42"
  }' \
  'http://localhost:8080/v2/send'
```

### Remote Delete

Delete a previously sent message.

```bash
curl -X DELETE -H "Content-Type: application/json" \
  -d '{
    "recipient": "+4354546464654",
    "timestamp": 1697123456789
  }' \
  'http://localhost:8080/v1/remote-delete/+431212131491291'

# Response: {"timestamp":"1697123457000"}
```

### API Configuration

Get and set API configuration including logging level and trust mode.

```bash
# Get configuration
curl -X GET 'http://localhost:8080/v1/configuration'

# Response:
# {
#   "logging": {
#     "Level": "info"
#   }
# }

# Set configuration (change log level)
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "logging": {
      "Level": "debug"
    }
  }' \
  'http://localhost:8080/v1/configuration'

# Get trust mode for account
curl -X GET 'http://localhost:8080/v1/configuration/+431212131491291/settings'

# Set trust mode (how to handle new identities)
curl -X POST -H "Content-Type: application/json" \
  -d '{
    "trust_mode": "on-first-use"
  }' \
  'http://localhost:8080/v1/configuration/+431212131491291/settings'
# Options: "on-first-use", "always", "never"
```

### API Info and Health

Get API version and health status.

```bash
# About endpoint
curl -X GET 'http://localhost:8080/v1/about'

# Response:
# {
#   "version": "v0.13.20",
#   "build": 12345,
#   "mode": "native",
#   "versions": ["v1", "v2"],
#   "capabilities": {
#     "sendMessages": ["v1", "v2"],
#     "groups": ["v1"]
#   }
# }

# Health check
curl -X GET 'http://localhost:8080/v1/health'
```

## Docker Deployment

### Basic Setup

Run Signal CLI REST API with Docker and persistent configuration.

```bash
# Create config directory
mkdir -p $HOME/.local/share/signal-api

# Start container (native mode - recommended)
docker run -d --name signal-api \
  --restart=always \
  -p 8080:8080 \
  -v $HOME/.local/share/signal-api:/home/.local/share/signal-cli \
  -e 'MODE=native' \
  bbernhard/signal-cli-rest-api

# JSON-RPC mode (fastest, higher memory)
docker run -d --name signal-api \
  --restart=always \
  -p 8080:8080 \
  -v $HOME/.local/share/signal-api:/home/.local/share/signal-cli \
  -e 'MODE=json-rpc' \
  bbernhard/signal-cli-rest-api

# Normal mode (slowest, lowest memory)
docker run -d --name signal-api \
  --restart=always \
  -p 8080:8080 \
  -v $HOME/.local/share/signal-api:/home/.local/share/signal-cli \
  -e 'MODE=normal' \
  bbernhard/signal-cli-rest-api
```

### Docker Compose

Complete docker-compose.yml configuration with environment variables.

```yaml
version: "3"
services:
  signal-cli-rest-api:
    image: bbernhard/signal-cli-rest-api:latest
    container_name: signal-api
    restart: always
    environment:
      - MODE=native  # Options: normal, native, json-rpc
      - AUTO_RECEIVE_SCHEDULE=0 22 * * *  # Auto-receive at 10pm daily
      - PORT=8080
      - LOG_LEVEL=info  # Options: debug, info, warn, error
      - DEFAULT_SIGNAL_TEXT_MODE=normal  # Options: normal, styled
      - SIGNAL_CLI_UID=1000
      - SIGNAL_CLI_GID=1000
      - SWAGGER_IP=localhost
      - SWAGGER_HOST=localhost:8080
    ports:
      - "8080:8080"
    volumes:
      - "./signal-cli-config:/home/.local/share/signal-cli"
    networks:
      - signal-net

networks:
  signal-net:
    driver: bridge
```

### Environment Variables

```bash
# Execution mode (affects performance)
MODE=native  # normal, native, json-rpc

# Auto-receive schedule (cron format) - only for normal/native modes
AUTO_RECEIVE_SCHEDULE=0 22 * * *

# Logging
LOG_LEVEL=info  # debug, info, warn, error

# Server configuration
PORT=8080
SWAGGER_IP=localhost
SWAGGER_HOST=localhost:8080
SWAGGER_USE_HTTPS_AS_PREFERRED_SCHEME=false

# Signal CLI configuration
SIGNAL_CLI_CONFIG_DIR=/home/.local/share/signal-cli/
SIGNAL_CLI_UID=1000
SIGNAL_CLI_GID=1000
SIGNAL_CLI_CHOWN_ON_STARTUP=true

# Text formatting
DEFAULT_SIGNAL_TEXT_MODE=normal  # normal or styled

# JSON-RPC specific
JSON_RPC_IGNORE_ATTACHMENTS=false
JSON_RPC_IGNORE_STORIES=true
JSON_RPC_TRUST_NEW_IDENTITIES=on-first-use  # on-first-use, always, never

# WebSocket webhook for receiving messages (json-rpc mode only)
RECEIVE_WEBHOOK_URL=  # Optional webhook URL for incoming messages
```

## Integration Examples

### Python Client Library

Using pysignalclirestapi for simplified Python integration.

```python
from pysignalclirestapi import SignalCliRestApi

# Initialize client
signal = SignalCliRestApi("http://localhost:8080", "+431212131491291")

# Send simple message
signal.send_message("Hello!", ["+4354546464654"])

# Send with attachment
with open("image.jpg", "rb") as f:
    attachment_data = f.read()
signal.send_message("Check this!", ["+4354546464654"],
                   base64_attachments=[attachment_data])

# Receive messages (blocking)
for message in signal.receive_messages():
    print(f"From: {message['source']}")
    print(f"Message: {message['message']}")

    # Download attachments
    if 'attachments' in message:
        for att in message['attachments']:
            data = signal.get_attachment(att['id'])
            with open(f"attachment_{att['id']}", "wb") as f:
                f.write(data)
```

### Home Assistant Integration

Send Signal notifications from Home Assistant automations.

```yaml
# configuration.yaml
notify:
  - name: signal
    platform: rest
    resource: http://localhost:8080/v2/send
    method: POST_JSON
    headers:
      Content-Type: application/json
    data:
      number: "+431212131491291"
      recipients:
        - "+4354546464654"
    message_param_name: message

# automation.yaml
automation:
  - alias: "Door opened notification"
    trigger:
      platform: state
      entity_id: binary_sensor.front_door
      to: "on"
    action:
      - service: notify.signal
        data:
          message: "Front door opened at {{ now().strftime('%H:%M') }}"

  # With image from camera
  - alias: "Motion detected with snapshot"
    trigger:
      platform: state
      entity_id: binary_sensor.motion_sensor
      to: "on"
    action:
      - service: camera.snapshot
        data:
          entity_id: camera.front_door
          filename: /tmp/snapshot.jpg
      - service: shell_command.send_signal_image

# shell_command in configuration.yaml
shell_command:
  send_signal_image: >
    curl -X POST -H "Content-Type: application/json"
    -d '{"message":"Motion detected!","number":"+431212131491291",
    "recipients":["+4354546464654"],
    "base64_attachments":["'$(base64 -w 0 /tmp/snapshot.jpg)'"]}'
    http://localhost:8080/v2/send
```

### Node.js Bot Example

Build a Signal chatbot using Node.js and WebSocket.

```javascript
const WebSocket = require('ws');
const axios = require('axios');

const API_URL = 'http://localhost:8080';
const NUMBER = '+431212131491291';

// Connect to receive messages
const ws = new WebSocket(`ws://localhost:8080/v1/receive/${NUMBER}`);

ws.on('message', async (data) => {
  const msg = JSON.parse(data);

  if (msg.envelope?.dataMessage?.message) {
    const sender = msg.envelope.source;
    const text = msg.envelope.dataMessage.message;

    console.log(`Received: ${text} from ${sender}`);

    // Bot commands
    if (text.startsWith('/')) {
      await handleCommand(text, sender);
    }
  }
});

async function handleCommand(command, sender) {
  let response = '';

  if (command === '/help') {
    response = 'Available commands: /help, /time, /weather';
  } else if (command === '/time') {
    response = `Current time: ${new Date().toLocaleString()}`;
  } else if (command === '/weather') {
    response = 'Weather: Sunny, 22°C';
  } else {
    response = 'Unknown command. Type /help for options.';
  }

  // Send response
  await axios.post(`${API_URL}/v2/send`, {
    message: response,
    number: NUMBER,
    recipients: [sender]
  });
}

ws.on('open', () => console.log('Connected to Signal'));
ws.on('error', (err) => console.error('WebSocket error:', err));
```

### Bash Script for Monitoring

Simple monitoring script with Signal notifications.

```bash
#!/bin/bash

SIGNAL_API="http://localhost:8080/v2/send"
MY_NUMBER="+431212131491291"
ALERT_RECIPIENT="+4354546464654"

send_signal() {
  local message="$1"
  curl -s -X POST -H "Content-Type: application/json" \
    -d "{\"message\":\"${message}\",\"number\":\"${MY_NUMBER}\",\"recipients\":[\"${ALERT_RECIPIENT}\"]}" \
    "${SIGNAL_API}"
}

# Check disk space
DISK_USAGE=$(df -h / | awk 'NR==2 {print $5}' | sed 's/%//')
if [ "$DISK_USAGE" -gt 90 ]; then
  send_signal "⚠️ ALERT: Disk usage at ${DISK_USAGE}%"
fi

# Check service status
if ! systemctl is-active --quiet nginx; then
  send_signal "🚨 CRITICAL: nginx service is down!"
fi

# Check website uptime
HTTP_CODE=$(curl -s -o /dev/null -w "%{http_code}" https://example.com)
if [ "$HTTP_CODE" != "200" ]; then
  send_signal "🔴 Website down! HTTP $HTTP_CODE"
fi
```

## Use Cases and Integration Patterns

Signal CLI REST API serves as a bridge between Signal Messenger's secure communication protocol and automated systems, enabling developers to build Signal-powered features without mobile app dependencies. Primary use cases include home automation notifications (smart home alerts, security camera events, sensor triggers), server monitoring and DevOps alerting (service failures, deployment status, performance thresholds), two-factor authentication and verification systems, customer support chatbots, automated broadcast messaging, and IoT device notifications. The WebSocket-based receive endpoint enables bidirectional communication for interactive bots and command-and-control interfaces.

Integration patterns typically follow three models: webhook-style push notifications (services POST to /v2/send), polling-based message retrieval (periodic GET requests or continuous receive subscriptions), and event-driven WebSocket connections for real-time bidirectional communication. The API's Docker-first architecture ensures easy deployment in containerized environments, while the three execution modes (normal/native/json-rpc) provide flexibility for different performance and resource requirements. Authentication and authorization are managed through phone number registration and device linking, with cryptographic keys stored in mounted volumes for persistence. Production deployments often place the API behind reverse proxies with TLS termination, implement rate limiting, and use environment-specific Signal accounts to separate development, staging, and production traffic.