Validate Customer Data

Validation helps ensure customers enter correct information, reducing fulfillment errors and support requests. Fungies supports two validation methods: regex patterns and custom validation URLs.

Regex Validation

Use regular expressions to validate text field input directly in the browser. Invalid input is rejected before the customer can submit.

How to Add Regex Validation

Edit your custom field in the Dashboard
Enter a regex pattern in the Regex field
Save your changes

Regex validation happens client-side, providing instant feedback to customers.

Common Patterns

Use Case	Pattern	Matches
Numbers only	`^[0-9]+$`	`12345`
Letters only	`^[a-zA-Z]+$`	`PlayerOne`
Alphanumeric	`^[a-zA-Z0-9]+$`	`Player123`
Username (3-20 chars)	`^[a-zA-Z0-9_]{3,20}$`	`cool_player_99`
Email	`^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$`	`user@example.com`
UUID	`^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$`	`550e8400-e29b-...`
Date (YYYY-MM-DD)	`^\d{4}-\d{2}-\d{2}$`	`2024-01-15`

Regex Tips

// Start (^) and end ($) anchors ensure the entire input matches
^[a-zA-Z0-9]+$   // ✓ Matches: "abc123"
                 // ✗ Rejects: "abc 123" (space not allowed)

// Character classes define allowed characters
[a-zA-Z]         // Any letter
[0-9] or \d      // Any digit
[a-zA-Z0-9_]     // Letters, digits, or underscore

// Quantifiers specify length
{3,20}           // Between 3 and 20 characters
+                // One or more
*                // Zero or more

Test your regex patterns at regex101.com before adding them to Fungies.

Custom Validation URL

For complex validation that can’t be expressed as regex—like checking if a player ID exists in your database—use a custom validation endpoint.

How It Works

Customer enters a value
Fungies sends a POST request to your validation URL
Your API checks if the value is valid
Return 200 OK for valid, any other status for invalid

Request Format

Fungies sends a POST request with the field value:

{
  "playerId": "Player_12345"
}

The key is your custom field’s identifier, and the value is what the customer entered.

Response

Status	Meaning
`200`	Valid - customer can proceed
`4xx` / `5xx`	Invalid - customer sees an error

Example Endpoint

// Express.js example
app.post('/validate/player-id', async (req, res) => {
  const { playerId } = req.body;
  
  // Check if player exists in your database
  const player = await db.players.findById(playerId);
  
  if (player) {
    return res.status(200).json({ valid: true });
  }
  
  return res.status(400).json({ 
    valid: false, 
    message: 'Player not found' 
  });
});

Securing Your Validation Endpoint

Without signature verification, anyone could call your validation endpoint. Always verify the signature in production.

Fungies signs validation requests the same way as webhooks. The signature is in the x-fngs-signature header:

x-fngs-signature: sha256_6808ed5be1262b60818359fa586145810d0793e8a677f1326520d3844e21b640

Verify the Signature

Use your validation URL secret (set in the Dashboard) to verify requests:

import crypto from 'crypto';

function verifySignature(payload, signature, secret) {
  const expectedSignature = 'sha256_' + crypto
    .createHmac('sha256', secret)
    .update(payload)
    .digest('hex');
    
  return crypto.timingSafeEqual(
    Buffer.from(signature),
    Buffer.from(expectedSignature)
  );
}

app.post('/validate/player-id', (req, res) => {
  const signature = req.headers['x-fngs-signature'];
  const rawBody = req.rawBody; // Must be raw, unparsed body
  
  if (!verifySignature(rawBody, signature, process.env.VALIDATION_SECRET)) {
    return res.status(401).json({ error: 'Invalid signature' });
  }
  
  // ... validation logic
});

See the webhook signature verification guide for more details.

Combining Validation Methods

You can use both regex and URL validation on the same field:

Regex runs first - Catches format errors instantly (client-side)
URL validation runs second - Checks business logic (server-side)

This gives customers fast feedback on format errors while still validating against your backend.

Developer Guides

Validate Customer Data

Regex Validation

How to Add Regex Validation

Common Patterns

Regex Tips

Custom Validation URL

How It Works

Request Format

Response

Example Endpoint

Securing Your Validation Endpoint

Verify the Signature

Combining Validation Methods

Next Steps

Custom Fields Setup

Webhook Setup

​Regex Validation

​How to Add Regex Validation

​Common Patterns

​Regex Tips

​Custom Validation URL

​How It Works

​Request Format

​Response

​Example Endpoint

​Securing Your Validation Endpoint

​Verify the Signature

​Combining Validation Methods

​Next Steps

Custom Fields Setup

Webhook Setup

Regex Validation

How to Add Regex Validation

Common Patterns

Regex Tips

Custom Validation URL

How It Works

Request Format

Response

Example Endpoint

Securing Your Validation Endpoint

Verify the Signature

Combining Validation Methods

Next Steps