github-webhook-bridge

An Azure Functions application that receives GitHub Webhooks and forwards them to Discord.

• Endpoints: POST / (webhook receiver), GET / (health check)
• Stack: C# / .NET 10 / Azure Functions v4 Isolated / Azure Table + Blob Storage
• Signature verification: HMAC-SHA256 (x-hub-signature-256, timing-safe comparison)

Setup

Prerequisites

• .NET 10 SDK
• Azure Functions Core Tools v4
• An Azure Storage account (for local development, Azurite can be used instead)
• A GitHub webhook secret
• A Discord webhook URL

Environment variables

Set these in src/local.settings.json (register them as application settings in the Azure production environment).

Key	Required	Description
GITHUB_WEBHOOK_SECRET	✅	HMAC-SHA256 signature verification secret
AzureWebJobsStorage	✅	Azure Storage connection string (use UseDevelopmentStorage=true locally)
DISCORD_WEBHOOK_URL	—	Default destination Discord webhook URL (fallback when ?url= is not specified)
DISABLED_EVENTS	—	Comma-separated event names to disable; can also be overridden via the ?disabled-events= query parameter
MUTES_FILE_PATH	—	Local file path for mute rules
MUTES_FILE_URL	—	HTTPS URL for mute rules
MUTES_BLOB	—	Azure Blob URI for mute rules
GITHUB_USER_MAP_FILE_PATH	—	Local file path for the GitHub→Discord user map
GITHUB_USER_MAP_FILE_URL	—	HTTPS URL for the user map
GITHUB_USER_MAP_BLOB	—	Azure Blob URI for the user map
APPLICATIONINSIGHTS_CONNECTION_STRING	—	Application Insights / Azure Monitor connection string

Running locally

dotnet restore
dotnet build

# Run tests
dotnet test -c Release

# Start Azure Functions locally (run from the src/ directory)
cd src && func start

Endpoint: http://localhost:7071/

Endpoints

Environment	URL
Production	https://<functionapp>.azurewebsites.net/
Local	http://localhost:7071/

• POST / (webhook receiver): Receives GitHub webhook events and forwards them to Discord.
• GET / (health check): Returns 200 OK with { "message": "book000/github-webhook-bridge is running" }.

Query parameters

Parameter	Description
url	Destination Discord webhook URL (only URLs starting with https://discord.com/api/webhooks/ or https://discordapp.com/api/webhooks/ are allowed)
disabled-events	Event names to disable for this request only (comma-separated)

Supported events

Implemented (12 types)

Event	Description
ping	Webhook registration check
push	Code push
pull_request	Pull request operations
pull_request_review	Pull request review
pull_request_review_comment	Review comment
pull_request_review_thread	Review thread resolve/reopen
issues	Issue operations
issue_comment	Issue / PR comment
discussion	Discussion
fork	Fork
public	Repository made public
star	Star

Any other event returns HTTP 406.

Mute rules

Notifications can be filtered per user. Rules are defined as a JSON array and specified via one of MUTES_FILE_PATH / MUTES_FILE_URL / MUTES_BLOB (priority order: Blob > URL > local file).

[
  {
    "userId": 123456789,
    "type": "include",
    "events": [
      { "eventName": "pull_request", "actions": ["opened", "closed"] }
    ]
  }
]

type	Behavior
include	Mute only the events/actions listed in events
exclude	Mute everything except the events/actions listed in events
all	Mute all notifications

If actions is omitted, all actions of that event are targeted.

GitHub→Discord user map

Mapping a GitHub user ID (numeric) to a Discord user ID lets notifications generate mentions. Defined as a JSON object and specified via one of GITHUB_USER_MAP_FILE_PATH / GITHUB_USER_MAP_FILE_URL / GITHUB_USER_MAP_BLOB.

{
  "1234567": "987654321098765432"
}

License

MIT