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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.

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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.

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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"
  }]
}

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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];
};

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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");
}

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Error Handling

The API returns standard HTTP status codes. Handle errors based on your application’s requirements.
StatusMeaningAction
400Bad requestCheck request parameters
401UnauthorizedVerify API key
403ForbiddenCheck service permissions or rate limits
500Server errorRetry 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));
        }
    }
};

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Integration Patterns

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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);
});

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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;
}

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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);

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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()
);

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Testing

Test with numbers in various formats and countries:
NumberCountryExpectedType
+441244657333GBValidLandline
+447700900123GBValidMobile
+14155552671USValidMobile
+441234567GBInvalidN/A

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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.

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Additional Resources