NuGet Package CAPTCHA

BotDetect CAPTCHA Generator protects ASP.NET/Core forms from spam.

The Captcha protection is available on .NET/Core for jQuery, Angular & React frontends and ASP.NET MVCCore, MVC1-5, WebForms & WebPages backends. It works in China; doesn't stalk; nor does it slurp your form-data -- think: GDPR & LGPD!

BotDetect uses many different image and sound algorithms for the generation of Captcha codes.

While each Captcha algorithm is easily comprehensible to human users, generating Captcha codes by random algorithm makes the Captcha challenge extremely difficult to pass automatically.

BotDetect provides an audio Captcha alternative to keep ASP.NET web applications accessible to the blind and other people for whom reading the Captcha code could be a problem, enabling you to make WCAG and Section 508 compliant websites.

BotDetect is a self-hosted .NET Captcha Component -- no 3rd-party servers are involved in the generation, displaying, and validation of Captcha challenges.
Therefore, BotDetect neither identify nor stalk your users and visitors -- nor does it slurp logins, passwords, and other data they fill in your forms.
This allows for the GDPR, LGPD, and CCPA compliant sites -- and also does miracles for the forms on any of the national security-sensitive ones.

* Out-of-the-box integrations with Angular, AngularJS, jQuery, and React frontend frameworks
* Produces XHTML 1.1 Strict, Section 508 and WCAG AAA compliant markup
* Fully compatible with ASP.NET Core 1.x and 2.x
* Fully compatible with legacy .NET 2.0 and onwards, .NET Core 1.x and .NET Core 2.x
* Fully compatible with ASP.NET MVC 1-5 and ASP.NET Core MVC (MVC 6)
* Fully compatible with ASP.NET WebForms
* Fully compatible with ASP.NET Web Pages
* Fully compatible with ASP.NET Ajax and jQuery Ajax validation
* Fully compatible with SharePoint Server / Foundation
* Visual Studio .NET 2017, 2015, 2013, 2012, 2010, 2008, 2005 and 2003 Designer support
* Medium trust environment support for shared servers
* Tested in Chrome, Firefox, Safari, IE, Edge and Opera browsers
* Full support for all Android & iOS devices
* Localized Captcha generation, using various Unicode character sets and downloadable multi-language sound pronunciations
* Custom Captcha image size, format, color scheme...
* Custom Captcha code length, style, character set, timeouts, generated code filtering...
* Many other randomization & customization options
* 60 secure & readable Captcha image styles
* 20 secure & accessible audio Captcha sound styles
* It works in China
* It does not identify and stalk your users and visitors
* It does not slurp your form data
* It allows for the GDPR, LGPD, and CCPA compliant sites
* Licensable source code

What nuget to use?
Please note that from the version 4.2 onward we have two BotDetect CAPTCHA nugets on the
* Use THIS nuget for ASP.NET applications running on the legacy .NET (non-Core) Frameworks
* Use THIS nuget for ASP.NET Core applications running on the .NET Core Frameworks
However, there is one special case that required the separate nuget.
* Use our NEW helper nuget INSTEAD OF this one for the special case of ASP.NET Core applications running on the legacy .NET (non-Core) Frameworks.
The new helper nuget name is and it is available at


Version: 4.4.2
Author(s): Captcha, Inc.
Last Update: Monday, July 22, 2019
.NET Fiddle: Create the first Fiddle
Project Url:
NuGet Url:

Install-Package Captcha
dotnet add package Captcha
paket add Captcha
Captcha Download (Unzip the "nupkg" after downloading)