A .NET 9 Minimal API application for collecting form submissions from static websites and storing them in PostgreSQL with extensible connector support for follow-up actions.
- Accepts form submissions via
multipart/form-dataandapplication/x-www-form-urlencoded - Stores form data dynamically in PostgreSQL using JSONB
- Captures client metadata (IP address, user agent, referer)
- CORS support with per-form domain restrictions
- Per-form rate limiting configuration
- Privacy mode for forms (no database persistence)
- Extensible connector system for follow-up actions (email, webhooks, etc.)
- Background task processing for async operations
- Connection resiliency with Polly retry policies
- Swagger UI for API documentation (configurable)
- .NET 9 SDK
- PostgreSQL database
- Entity Framework Core tools (for migrations)
- Install EF Core tools (if not already installed):
dotnet tool install --global dotnet-ef- Configure PostgreSQL connection in
appsettings.json:
{
"ConnectionStrings": {
"PostgreSQL": "Host=localhost;Database=formfeeder;Username=postgres;Password=postgres"
}
}- Apply database migrations:
cd FormFeeder.Api
dotnet ef database update- Run the application:
dotnet runThe API will be available at https://localhost:5500 (HTTPS only in development).
# Pull the latest image
docker pull ghcr.io/yourusername/formfeeder-oss:latest
# Run the container
docker run -d \
--name formfeeder \
-p 8080:8080 \
-e ConnectionStrings__PostgreSQL="Host=host.docker.internal;Database=formfeeder;Username=postgres;Password=yourpassword" \
-e MailJet__ApiKey="your-api-key" \
-e MailJet__ApiSecret="your-api-secret" \
ghcr.io/yourusername/formfeeder-oss:latest# Build the Docker image
docker build -t formfeeder ./FormFeeder.Api
# Run with docker-compose (recommended for development)
docker-compose up -d
# Or run standalone
docker run -d \
--name formfeeder \
-p 8080:8080 \
-e ASPNETCORE_ENVIRONMENT=Development \
-e ConnectionStrings__PostgreSQL="Host=host.docker.internal;Database=formfeeder;Username=postgres;Password=yourpassword" \
formfeederlatest- Latest stable releasev1.0.0,v1.1.0, etc. - Specific version tagsmain-<sha>- Development builds from main branch
- POST
/api/form/{formId} - Content-Type:
application/x-www-form-urlencodedormultipart/form-data - Path Parameter:
formId- Unique identifier for the form/website
<form action="https://localhost:5500/api/form/contact-form" method="POST">
<input type="text" name="name" required>
<input type="email" name="email" required>
<textarea name="message"></textarea>
<button type="submit">Submit</button>
</form>const formData = new FormData();
formData.append('name', 'John Doe');
formData.append('email', 'john@example.com');
formData.append('message', 'Hello!');
fetch('https://localhost:5500/api/form/contact-form', {
method: 'POST',
body: formData
})
.then(response => response.json())
.then(data => console.log('Success:', data))
.catch(error => console.error('Error:', error));Open test-form.html in a browser to test the API with sample forms.
When enabled in configuration, access Swagger UI at:
https://localhost:5500/swagger
Enable/disable Swagger in appsettings.json:
{
"EnableSwagger": true
}Configure forms with their specific settings in appsettings.json:
{
"Forms": [
{
"FormId": "contact-form",
"AllowedDomains": ["https://example.com", "*"],
"Description": "Contact form from main website",
"Enabled": true,
"PrivacyMode": false, // Set to true to skip database persistence
"RateLimit": {
"RequestsPerWindow": 100,
"WindowMinutes": 1
},
"Connectors": [
{
"Type": "MailJet",
"Name": "EmailNotification",
"Enabled": true,
"Settings": {
"ApiKey": "your-api-key",
"ApiSecret": "your-api-secret",
"FromEmail": "no-reply@example.com",
"ToEmail": "admin@example.com",
"Subject": "New Form Submission",
"TemplateId": "optional-template-id"
}
},
{
"Type": "Slack",
"Name": "SlackNotification",
"Enabled": true,
"Settings": {
"WebhookUrl": "https://hooks.slack.com/services/YOUR/WEBHOOK/URL",
"Username": "FormFeeder",
"IconEmoji": ":incoming_envelope:"
}
}
]
}
]
}Configure per-form rate limits to prevent abuse:
{
"RateLimit": {
"RequestsPerWindow": 100, // Number of allowed requests
"WindowMinutes": 1 // Time window in minutes
}
}Enable privacy mode to process form submissions without storing them in the database:
{
"FormId": "gdpr-compliant-form",
"PrivacyMode": true, // Submissions sent to connectors only, not stored in DB
"Connectors": [
{
"Type": "Slack",
"Enabled": true,
// ... connector settings
}
]
}Important: Privacy mode requires at least one enabled connector. If no connectors are enabled, privacy mode will be automatically disabled with a warning.
FormFeeder supports extensible connectors that execute after successful form submissions. Connectors run asynchronously in the background to avoid blocking the form submission response.
Sends form submissions to Slack channels via incoming webhooks:
- Rich message formatting with attachments
- Customizable username and emoji
- Field-by-field display with smart formatting
- Optional raw JSON data inclusion
- Automatic field name formatting (camelCase/snake_case to Title Case)
Configuration:
{
"Type": "Slack",
"Settings": {
"WebhookUrl": "https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXX",
"Channel": "#form-submissions", // Optional: Override default channel
"Username": "FormFeeder Bot", // Optional: Bot username (default: "FormFeeder")
"IconEmoji": ":email:", // Optional: Bot emoji (default: ":envelope:")
"IncludeRawJson": "true" // Optional: Include raw JSON (default: "false")
}
}To get a webhook URL:
- Go to your Slack workspace settings
- Navigate to "Apps" → "Incoming Webhooks"
- Create a new webhook and select the target channel
- Copy the webhook URL
Sends email notifications using the MailJet API:
- Supports both template-based and content-based emails
- Template variables include all form fields as a dictionary
- Automatic retry on transient failures
Configuration:
{
"Type": "MailJet",
"Settings": {
"ApiKey": "your-mailjet-api-key",
"ApiSecret": "your-mailjet-api-secret",
"FromEmail": "sender@example.com",
"FromName": "Your App Name",
"ToEmail": "recipient@example.com",
"ToName": "Recipient Name",
"Subject": "New Form Submission",
"TemplateId": "7251954" // Optional: Use MailJet template
}
}When using a MailJet template, the following variables are available:
{{var:formId}}- The form identifier{{var:submittedAt}}- Submission timestamp{{var:ipAddress}}- Client IP address{{var:userAgent}}- Browser user agent{{var:referer}}- Referring URL{{var:formData}}- Raw JSON of all form fields{{var:formFields}}- Dictionary for iteration:{% for key, value in var:formFields %} <tr> <td>{{key}}</td> <td>{{value}}</td> </tr> {% endfor %}
Implement the IConnector interface to create custom connectors:
public interface IConnector
{
string Type { get; }
string Name { get; }
bool Enabled { get; set; }
Task<ConnectorResult> ExecuteAsync(
FormSubmission submission,
Dictionary<string, object>? configuration = null
);
}Example custom connector:
public class WebhookConnector : IConnector
{
public string Type => "Webhook";
public string Name { get; private set; }
public bool Enabled { get; set; } = true;
public async Task<ConnectorResult> ExecuteAsync(
FormSubmission submission,
Dictionary<string, object>? configuration = null)
{
// Your webhook implementation
return ConnectorResult.Successful("Webhook sent");
}
}Register your connector in Program.cs:
builder.Services.AddScoped<IConnector, WebhookConnector>();FormFeeder.Api/
├── Connectors/
│ ├── IConnector.cs # Connector interface
│ ├── MailJetConnector.cs # MailJet email connector
│ └── TransactionalEmails.cs # MailJet helper classes
├── Data/
│ └── AppDbContext.cs # EF Core database context
├── Models/
│ ├── FormSubmission.cs # Entity model
│ ├── FormConfiguration.cs # Form config model
│ └── ConnectorResult.cs # Connector result model
├── Services/
│ ├── FormSubmissionService.cs # Form submission logic
│ ├── ConnectorService.cs # Connector orchestration
│ ├── BackgroundTaskQueue.cs # Async task processing
│ └── EmailTemplateService.cs # Email template generation
├── Endpoints/
│ └── FormEndpoints.cs # API endpoints
├── Migrations/ # EF Core migrations
├── Program.cs # Application startup
└── appsettings.json # Configuration
Below are some products that are built with or actively integrate the FormFeeder.io open source form submission engine. If you want your product listed, make sure that you actually use FormFeeder and submit a PR.
| Product | Website | Company | Built with | Notes |
|---|---|---|---|---|
| Aurora | AuroraHQ.ai | Amaretto Software Labs | Create high-fidelity product prototypes using AI. | |
| Borealis | BorealisHQ.io | Amaretto Software Labs | AI Sandboxes and infrastructure on demand. | |
| Cobalt Coder | cobaltcode.ai | Amaretto Software Labs | A barebone coding agent CLI built for speed, control, and no limitations. | |
| Dawn | DawnHQ.ai | Amaretto Software Labs | Team knowledge agent, get instant answers from your codebase, infrastructure, and connected systems — directly in Slack, Teams or Telegram. | |
| Enclave | EnclaveHQ.io | Amaretto Software Labs | Run protected apps in a secure environment via remote browser isolation. | |
| Entity | EntityHQ.ai | Amaretto Software Labs | AI Agent orchestrator for building AI native Companies | |
| FormFeeder | FormFeeder.io | Amaretto Software Labs | Form handling for static websites with privacy and security by default. A hosted version with a control panel for FormFeeder OSS |
