Phone Validation Best Practices

Build custom phone validation workflows using the Loqate API. This guide covers implementation patterns and integration strategies for JavaScript, PHP, and .NET. For pre-built solutions, see Tag integrations or platform integrations. Security and configuration details are in API Security.

These examples demonstrate core integration patterns. Adapt error handling and configuration for your production environment.

Architecture Decisions

Client-side validation
Quick to implement and requires less technical expertise, but exposes your API key in client code. Mitigate with domain restrictions in account settings. Best for real-time form validation. Server-side validation
Keeps credentials secure and provides full control over validation logic. Best for backend workflows and batch processing.

API Overview

Phone Validation uses a single endpoint that returns validation status, carrier information, and formatted numbers. Endpoint: POST /PhoneNumberValidation/Interactive/Validate/v2.20/json6.ws Parameters:

Key - Your API key
Phone - Phone number to validate
Country - ISO country code (optional if number includes country prefix)

Response:

{
  "Items": [{
    "PhoneNumber": "+441244657333",
    "IsValid": "Yes",
    "NetworkName": "BT",
    "NetworkCountry": "GB",
    "NationalFormat": "01244 657333",
    "NumberType": "Landline"
  }]
}

Basic Implementation

const validatePhone = async (phone, country = "GB") => {
    const response = await fetch(
        'https://services.postcodeanywhere.co.uk/PhoneNumberValidation/Interactive/Validate/v2.20/json3.ws',
        {
            method: 'POST',
            headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
            body: new URLSearchParams({
                Key: process.env.LOQATE_API_KEY,
                Phone: phone,
                Country: country
            })
        }
    );
    
    const data = await response.json();
    return data.Items[0];
};

<?php
function validatePhone($phone, $country = 'GB') {
    $ch = curl_init('https://services.postcodeanywhere.co.uk/PhoneNumberValidation/Interactive/Validate/v2.20/json3.ws');
    
    curl_setopt_array($ch, [
        CURLOPT_POST => true,
        CURLOPT_POSTFIELDS => http_build_query([
            'Key' => getenv('LOQATE_API_KEY'),
            'Phone' => $phone,
            'Country' => $country
        ]),
        CURLOPT_RETURNTRANSFER => true
    ]);
    
    $response = curl_exec($ch);
    curl_close($ch);
    
    return json_decode($response, true)['Items'][0];
}
?>

public async Task<PhoneValidationResult> ValidatePhone(string phone, string country = "GB")
{
    using var client = new HttpClient();
    
    var parameters = new Dictionary<string, string>
    {
        ["Key"] = Environment.GetEnvironmentVariable("LOQATE_API_KEY"),
        ["Phone"] = phone,
        ["Country"] = country
    };
    
    var response = await client.PostAsync(
        "https://services.postcodeanywhere.co.uk/PhoneNumberValidation/Interactive/Validate/v2.20/json3.ws",
        new FormUrlEncodedContent(parameters)
    );
    
    var data = await response.Content.ReadAsStringAsync();
    return JsonSerializer.Deserialize<PhoneValidationResponse>(data).Items[0];
}

Handling Results

The IsValid field returns "Yes", "No", or "Maybe". A "Maybe" response indicates temporary carrier network issues—treat it as potentially valid.

const result = await validatePhone("+441244657333");

if (result.IsValid === "Yes") {
    console.log(`Valid ${result.NumberType}: ${result.NationalFormat}`);
} else if (result.IsValid === "Maybe") {
    console.log("Validation incomplete - network unavailable");
} else {
    console.log("Invalid number");
}

<?php
$result = validatePhone('+441244657333');

if ($result['IsValid'] === 'Yes') {
    echo "Valid {$result['NumberType']}: {$result['NationalFormat']}";
} elseif ($result['IsValid'] === 'Maybe') {
    echo "Validation incomplete - network unavailable";
} else {
    echo "Invalid number";
}
?>

var result = await ValidatePhone("+441244657333");

if (result.IsValid == "Yes")
{
    Console.WriteLine($"Valid {result.NumberType}: {result.NationalFormat}");
}
else if (result.IsValid == "Maybe")
{
    Console.WriteLine("Validation incomplete - network unavailable");
}
else
{
    Console.WriteLine("Invalid number");
}

Error Handling

The API returns standard HTTP status codes. Handle errors based on your application’s requirements.

Status	Meaning	Action
400	Bad request	Check request parameters
401	Unauthorized	Verify API key
403	Forbidden	Check service permissions or rate limits
500	Server error	Retry with exponential backoff

Retry logic:

const validateWithRetry = async (phone, country, maxRetries = 3) => {
    for (let i = 0; i < maxRetries; i++) {
        try {
            return await validatePhone(phone, country);
        } catch (error) {
            if (error.status < 500 || i === maxRetries - 1) throw error;
            await new Promise(r => setTimeout(r, Math.pow(2, i) * 1000));
        }
    }
};

Integration Patterns

Real-Time Form Validation

Validate phone numbers on blur with debouncing to reduce API calls.

let timeout;
phoneInput.addEventListener('blur', (e) => {
    clearTimeout(timeout);
    timeout = setTimeout(async () => {
        const result = await validatePhone(e.target.value);
        updateUI(result.IsValid === "Yes");
    }, 500);
});

Batch Validation

Process multiple numbers with rate limiting.

function validateBatch($phones, $country = 'GB') {
    $results = [];
    foreach ($phones as $phone) {
        $results[] = [
            'phone' => $phone,
            'result' => validatePhone($phone, $country)
        ];
        usleep(100000); // 100ms delay between requests
    }
    return $results;
}

Multi-Country Support

Auto-detect user location and adjust validation accordingly.

const detectCountry = async () => {
    const response = await fetch('https://ipapi.co/json/');
    const data = await response.json();
    return data.country_code;
};

const country = await detectCountry();
const result = await validatePhone(phoneNumber, country);

Data Storage

Store validated numbers in international format for consistency.

CREATE TABLE phone_numbers (
    id SERIAL PRIMARY KEY,
    international VARCHAR(20),
    national VARCHAR(20),
    country_code VARCHAR(3),
    number_type VARCHAR(10),
    is_valid BOOLEAN,
    validated_at TIMESTAMP DEFAULT NOW()
);

Testing

Test with numbers in various formats and countries:

Number	Country	Expected	Type
+441244657333	GB	Valid	Landline
+447700900123	GB	Valid	Mobile
+14155552671	US	Valid	Mobile
+441234567	GB	Invalid	N/A

Security

Configure API key restrictions in your account settings:

Add domain restrictions for client-side implementations
Use IP allowlists for server-side implementations
Set rate limits to prevent abuse
Rotate keys periodically

See API Security for detailed guidance.

Overview

Location Solutions

Data Validation

Resources

Phone Validation Best Practices

Architecture Decisions

API Overview

Basic Implementation

Handling Results

Error Handling

Integration Patterns

Real-Time Form Validation

Batch Validation

Multi-Country Support

Data Storage

Testing

Security

Additional Resources

​Architecture Decisions

​API Overview

​Basic Implementation

​Handling Results

​Error Handling

​Integration Patterns

​Real-Time Form Validation

​Batch Validation

​Multi-Country Support

​Data Storage

​Testing

​Security

​Additional Resources

Architecture Decisions

API Overview

Basic Implementation

Handling Results

Error Handling

Integration Patterns

Real-Time Form Validation

Batch Validation

Multi-Country Support

Data Storage

Testing

Security

Additional Resources