Forms & Files

Supported content types and file behavior across privacy vs persisted modes.

Supported Content Types

FormFeeder accepts multiple content types to accommodate different client implementations:

application/json

Best for JavaScript/AJAX submissions with structured data.

fetch(url, {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    name: "John Doe",
    email: "[email protected]",
    message: "Hello World"
  })
})

✅ Supports nested objects and arrays
❌ No file uploads

application/x-www-form-urlencoded

Default for HTML forms without files.

<form action="https://api.formfeeder.io/v1/form/abc123" method="POST">
  <input name="name" value="John Doe">
  <input name="email" value="[email protected]">
  <button type="submit">Submit</button>
</form>

✅ Simple key-value pairs
❌ No file uploads
❌ No nested data

multipart/form-data

Required for file uploads and mixed content.

<form action="https://api.formfeeder.io/v1/form/abc123" method="POST" enctype="multipart/form-data">
  <input name="name" value="John Doe">
  <input name="email" value="[email protected]">
  <input type="file" name="attachment">
  <button type="submit">Submit</button>
</form>

✅ File uploads supported
✅ Mixed content types
❌ Larger payload size

File Upload Support

FormFeeder provides comprehensive file upload capabilities with security and performance optimizations.

Default File Limits

Supported File Types

Images

• .jpg, .jpeg - JPEG images
• .png - PNG images
• .gif - GIF images
• .webp - WebP images
• .svg - SVG vector graphics (sanitized)

Documents

• .pdf - PDF documents
• .doc, .docx - Microsoft Word
• .txt - Plain text files
• .rtf - Rich text format

Spreadsheets

• .xls, .xlsx - Microsoft Excel
• .csv - Comma-separated values
• .ods - OpenDocument Spreadsheet

Archives

• .zip - ZIP archives
• .rar - RAR archives (read-only)

Custom Types

Additional file types can be configured per form through the dashboard or API.

File Validation

FormFeeder performs multiple validation layers:

1. MIME Type Detection: Server-side content type validation
2. Extension Verification: File extension allowlist checking
3. Size Limits: Per-file and total size enforcement
4. Content Scanning: Basic malware detection (enterprise plans)

File Storage Architecture

Privacy Mode (Default for Private Forms)

graph LR
    A[Form Submission] --> B[Temporary Storage]
    B --> C[Connector Processing]
    C --> D[Automatic Cleanup]
    
    B -.-> E[24hr Cleanup Job]
    E --> D

• Files stored in temporary Azure Blob container
• Available during connector execution only
• Automatically deleted after processing
• No permanent file storage or access URLs
• Perfect for GDPR compliance

Regular Mode (Dashboard Forms)

graph LR
    A[Form Submission] --> B[Permanent Storage]
    B --> C[Connector Processing]
    B --> D[File Access URLs]
    B --> E[Configurable Retention]

• Files stored in persistent Azure Blob container
• Access URLs generated for downloads
• Configurable retention periods
• Analytics and management features
• Team sharing capabilities

File Handling by Destination

Email (MailJet)

• Attachments: Files attached directly to email
• Size Limits: 8MB total across all attachments
• File Limits: Maximum 5 files per email
• Behavior: Files exceeding limits are skipped with warning logs
• Format: Files sent as email attachments with original names

Configuration Example

{
  "type": "MailJet",
  "config": {
    "to": "[email protected]",
    "subject": "New Form with Attachments",
    "includeAttachments": true,
    "maxAttachments": 5,
    "maxAttachmentSize": 8388608
  }
}

Slack

• File Metadata: Shows file information in message
• No Uploads: Files are not uploaded to Slack workspace
• Display Format: Filename, size, content type shown in attachments
• File Links: Download links included (regular mode only)

Example Slack Message

📝 New Form Submission

Name: John Doe
Email: [email protected]
Message: Please find my resume attached.

📎 Attachments:
• resume.pdf (245 KB, application/pdf)
• portfolio.zip (1.2 MB, application/zip)

Webhooks

• File URLs: Temporary or permanent URLs provided in payload
• Access Duration: 24 hours (privacy) or configurable (regular)
• Metadata: Complete file information included
• Download: Your webhook endpoint downloads files using provided URLs

Webhook Payload Example

{
  "formId": "abc123",
  "submissionId": "sub_def456",
  "data": {
    "name": "John Doe",
    "email": "[email protected]"
  },
  "files": [
    {
      "fieldName": "resume",
      "filename": "resume.pdf",
      "contentType": "application/pdf",
      "size": 245760,
      "url": "https://files.formfeeder.io/temp/abc123/resume.pdf"
    }
  ]
}

Form Field Types

FormFeeder handles various HTML form field types automatically:

Text Fields

<input type="text" name="name">
<input type="email" name="email">
<input type="tel" name="phone">
<input type="url" name="website">

Selection Fields

<select name="country">
  <option value="us">United States</option>
  <option value="ca">Canada</option>
</select>

<input type="radio" name="size" value="small">
<input type="radio" name="size" value="large">

<input type="checkbox" name="newsletter" value="yes">

File Fields

<!-- Single file -->
<input type="file" name="document">

<!-- Multiple files -->
<input type="file" name="images" multiple>

<!-- Restricted types -->
<input type="file" name="resume" accept=".pdf,.doc,.docx">

Advanced Fields

<textarea name="message"></textarea>
<input type="number" name="quantity">
<input type="date" name="birthdate">
<input type="hidden" name="source" value="website">

Data Processing Rules

Field Name Normalization

• Field names are case-sensitive and preserved as-is
• Special characters allowed: -, _, .
• Unicode field names supported
• Array notation supported: items[], person[name]

Value Processing

// String fields
"name" => "John Doe"

// Multiple values (checkboxes, multi-select)
"interests[]" => ["coding", "music", "travel"]

// File fields
"resume" => {
  "filename": "resume.pdf",
  "contentType": "application/pdf",
  "size": 245760
}

Empty Field Handling

• Empty strings are preserved
• Unchecked checkboxes are omitted
• Unselected radio buttons are omitted
• Empty file fields are omitted

Security Considerations

File Upload Security

1. Content Type Validation: MIME type detection prevents disguised files
2. Extension Filtering: Allowlist prevents execution of dangerous files
3. Size Limits: Prevent resource exhaustion attacks
4. Virus Scanning: Enterprise plans include malware detection
5. Sandboxed Storage: Files stored in isolated environment

Form Injection Protection

• XSS Prevention: All form data sanitized before processing
• SQL Injection: Parameterized queries used throughout
• CSRF Protection: Origin validation required
• Rate Limiting: Prevents spam and abuse

Best Practices

For File Uploads

• Always specify accept attribute on file inputs
• Set reasonable file size limits for your use case
• Use HTTPS for all form submissions
• Validate file types on client side for better UX

For Form Design

• Use appropriate input types (email, tel, etc.)
• Include client-side validation for immediate feedback
• Implement proper error handling for failed submissions
• Consider progressive enhancement for JavaScript-dependent features

Testing File Uploads

Local Development

# Test basic form submission
curl -X POST "https://api.formfeeder.io/v1/form/test123" \
  -F "name=Test User" \
  -F "[email protected]" \
  -F "file=@/path/to/test.pdf"

Browser Testing

// JavaScript file upload test
const formData = new FormData();
formData.append('name', 'Test User');
formData.append('file', fileInput.files[0]);

fetch('https://api.formfeeder.io/v1/form/test123', {
  method: 'POST',
  body: formData
}).then(response => {
  console.log('Upload successful:', response.ok);
});

Error Scenarios

Test these common error scenarios:

• File too large (should return 413 status)
• Unsupported file type (should return 400 status)
• Too many files (should return 400 status)
• Network timeout during upload
• Invalid form data combined with files