Blazorise Captcha component

Integrate simple captchas into your Blazor applications with the Blazorise Captcha component.

This extension supports multiple captcha providers, enabling the addition of captcha functionality with provider-specific settings.

Supported Captcha providers

  • Google reCAPTCHA Implemented via Blazorise.Captcha.ReCaptcha


1. General Installation

Install the base captcha extension from NuGet.
Install-Package Blazorise.Captcha

2. Provider-Specific Installation

Install the ReCaptcha provider extension from NuGet.
Install-Package Blazorise.Captcha.ReCaptcha

3. Registering Services for reCAPTCHA

Incorporate ReCaptcha services by adding the following code to the relevant sections of Program.cs.
using Blazorise.Captcha.ReCaptcha;

	.AddBlazorise( options =>
		options.Immediate = true;
	} )
	.AddBlazoriseGoogleReCaptcha( reCaptchaOptions =>
		reCaptchaOptions.SiteKey = Configuration["ReCaptchaSiteKey"]
		//Set any other ReCaptcha options here...

4. Imports

In your main _Imports.razor, ensure you include:
@using Blazorise.Captcha

5. Static Files - ReCaptcha

Modify your project's HTML template to include the google reCAPTCHA js files. The files you add depend on whether you're working with a WebAssembly or Server project:

  • For WebAssembly, update index.html.
  • For Server, update _Layout.cshtml or _Host.cshtml.
  • For .NET 8, update App.razor.

Google reCAPTCHA docs recommend adding the script to the end of the <head> tag with async and defer attributes.

<script src="" async defer></script>


ReCaptcha Checkbox

The following example demonstrates how to use the ReCaptcha integration. You can use the ReCaptchaOptions to configure the widget according to your needs.
@using Microsoft.Extensions.Options
@using System.Text.Json

<Div Flex="Flex.AlignItems.Center" Gap="Gap.Is3">
    <Captcha @ref="@captcha" Solved="@Solved" Validate="@Validate" Expired="Expired" />

    <Button Background="Background.Primary" Clicked="@Reset">
@code {
    [Inject] IOptions<AppSettings> AppSettings { get; set; }

    [Inject] IHttpClientFactory HttpClientFactory { get; set; }

    private Captcha captcha;

    private void Solved( CaptchaState state )
        Console.WriteLine( $"Captcha Success: {state.Valid}" );

    private void Expired()
        Console.WriteLine( "Captcha Expired" );

    private async Task<bool> Validate( CaptchaState state )
        Console.WriteLine( "Captcha Validate" );

        //Perform server side validation
        //You should make sure to implement server side validation
        //Here's a simple example:
        var content = new FormUrlEncodedContent( new[]
            new KeyValuePair<string, string>("secret", AppSettings.Value.ReCaptchaServerKey),
            new KeyValuePair<string, string>("response", state.Response),
         } );

        var httpClient = HttpClientFactory.CreateClient();
        var response = await httpClient.PostAsync( "", content );

        var result = await response.Content.ReadAsStringAsync();
        var googleResponse = JsonSerializer.Deserialize<GoogleResponse>( result, new JsonSerializerOptions()
                PropertyNamingPolicy = JsonNamingPolicy.CamelCase
            } );

        return googleResponse.Success;

    private async Task Reset()
        await captcha.Reset();

    public class GoogleResponse
        public bool Success { get; set; }
        public double Score { get; set; } //V3 only - The score for this request (0.0 - 1.0)
        public string Action { get; set; } //v3 only - An identifier
        public string Challenge_ts { get; set; }
        public string Hostname { get; set; }
        public string ErrorCodes { get; set; }



Name Description Type Default
State The current state of the Captcha. CaptchaState
Solved A Captcha solved event. Provides contextual information about the Captcha state after the user has solved. EventCallback<CaptchaState>
Validate A Captcha validation event. Further validation may be performed here. Func<CaptchaState, Task<bool>>
Expired The Captcha expired event. EventCallback


Name DescriptionReturnParameters
Submit Submits the Captcha. Task
Reset Resets the Captcha. Task


Name Description Type Default
SiteKey The client side api key for google reCAPTCHA. string
Size The size of the widget. ReCaptchaSize ReCaptchaSize.Normal
Theme The color theme of the widget. ReCaptchaTheme ReCaptchaTheme.Light
BadgePosition Reposition the reCAPTCHA badge. 'inline' lets you position it with CSS. This option is only available for invisible reCAPTCHA. ReCaptchaBadgePosition ReCaptchaBadgePosition.BottomEnd
LanguageCode Refer to: Defaults to: 'en' (English (US)) string en
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