ip-api.io .NET SDK
dotnet add package IpApiIo

Add the official IpApiIo package from NuGet. It has zero package dependencies — it's built on the framework's own HttpClient and System.Text.Json.

dotnet add package IpApiIo

# ...or add to your .csproj:
# <PackageReference Include="IpApiIo" Version="1.*" />

Bring the namespace into scope and build one IpApiClient with your API key. Read the key from an environment variable — never hardcode it. The API rejects keyless requests with 401.

using IpApiIo;

var apiKey = Environment.GetEnvironmentVariable("IP_API_IO_KEY")!;
var client = new IpApiClient(apiKey);

// ... use the client ...

IpApiClient wraps a single HttpClient and is thread-safe — register it as a singleton (or reuse one instance) instead of creating one per request. In ASP.NET Core, add it once in Program.cs:

builder.Services.AddSingleton(
    new IpApiClient(builder.Configuration["IpApiIo:Key"]!));

Call LookupAsync(ip) for any IPv4 or IPv6 address, or LookupAsync() to resolve the caller's own IP. Responses are strongly-typed objects; nullable fields are string? / double? — null-check before use.

var info = await client.LookupAsync("8.8.8.8");

Console.WriteLine(info.Ip);                          // "8.8.8.8"
Console.WriteLine(info.Isp);                         // "Google LLC"
Console.WriteLine(info.Location.Country);            // "United States"
Console.WriteLine(info.SuspiciousFactors.IsDatacenter); // True

// Resolve the caller's own IP:
var me = await client.LookupAsync();
Console.WriteLine(me.Ip);

The SuspiciousFactors object carries seven boolean fields on every lookup — this is what sets ip-api.io apart from plain geolocation APIs. You get security intelligence in the same call, at no extra cost.

var info = await client.LookupAsync("185.220.101.45"); // example Tor exit node
var f = info.SuspiciousFactors;

if (f.IsVpn || f.IsProxy || f.IsTorNode)
    Console.WriteLine("Anonymized traffic — consider a CAPTCHA or block");
if (f.IsDatacenter)
    Console.WriteLine("Cloud/datacenter IP — likely automated");
if (f.IsThreat)
    Console.WriteLine("Active threat signal — block this request");

var risky = f.IsVpn || f.IsProxy || f.IsTorNode || f.IsThreat;

Need to check many IPs at once? LookupBatchAsync takes up to 100 addresses in a single request:

var batch = await client.LookupBatchAsync(
    new[] { "8.8.8.8", "1.1.1.1", "9.9.9.9" });

Console.WriteLine($"{batch.TotalProcessed} {batch.SuccessfulLookups}");

foreach (var (ip, result) in batch.Results)
    Console.WriteLine($"{ip} {result.SuspiciousFactors.IsVpn}");

The client throws typed exceptions that all derive from IpApiException and never retries on its own, so on a rate limit RateLimitException.Reset tells you exactly when to try again.

using IpApiIo;
using IpApiIo.Exceptions;

try
{
    var info = await client.LookupAsync("8.8.8.8");
    Console.WriteLine(info.Ip);
}
catch (RateLimitException ex)
{
    Console.WriteLine($"Rate limited. Remaining: {ex.Remaining}. Resets at {ex.Reset}");
}
catch (AuthenticationException)
{
    Console.WriteLine("Invalid or missing API key — get one free at https://ip-api.io");
}
catch (IpApiException ex)
{
    // Invalid request, server error, or transport failure
    Console.WriteLine($"ip-api.io error: {ex.Message}");
}

In an ASP.NET Core minimal API, run the lookup server-side and pass the real client IP from the X-Forwarded-For header:

app.MapGet("/check", async (HttpContext ctx, IpApiClient client) =>
{
    var clientIp = ctx.Request.Headers["X-Forwarded-For"]
        .FirstOrDefault()?.Split(',')[0].Trim()
        ?? ctx.Connection.RemoteIpAddress?.ToString()
        ?? "0.0.0.0";

    try
    {
        var info = await client.LookupAsync(clientIp);
        return Results.Ok(new
        {
            ip = info.Ip,
            country = info.Location.Country,
            isVpn = info.SuspiciousFactors.IsVpn,
            isThreat = info.SuspiciousFactors.IsThreat
        });
    }
    catch (IpApiException)
    {
        // Treat ip-api.io as a non-critical dependency
        return Results.Ok(new { ip = clientIp, country = (string?)null });
    }
});