.Net Captcha

Microsoft’s cross-platform runtime and libraries for creating cloud, desktop and server solutions in languages like C# and F#.Drop TrustCaptcha into any .NET workload for privacy-friendly, GDPR-aligned protection that blocks bots with proof-of-work and scoring yet stays invisible to customers.

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TrustCaptcha is the privacy friendly and user focused CAPTCHA for .Net

Security & Bot-ScoreTrustCaptcha combines a proof-of-work with a bot score — similar to the reCAPTCHA score — and custom security configurations for maximum security. Learn more about the CAPTCHA security concept

Privacy Friendly & GDPR-CompliantTrustCaptcha is a privacy-first CAPTCHA solution with a clear focus on data protection and GDPR compliance. Learn more about the GDPR-compliant CAPTCHA

CustomizationAll features of the CAPTCHA widget are fully customizable such as translations or design. The branding or the entire widget can also be hidden. Learn more about the customization

AccessibilityThe CAPTCHA completely dispenses with puzzles or image marking tasks. The CAPTCHA works fully automated and complies with international accessibility standards. Learn more about the accessibility

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Integrate TrustCaptcha in .Net

Integrate TrustCaptcha with .Net quickly and easily into your website, application or platform in just a few steps and effectively protect your online presence and services from bot abuse.

1 – Sign in or sign up
The first thing you need to do is sign in to your Trustcomponent account. If you do not yet have a Trustcomponent account, you can register with us quickly and easily in just a few steps. After that, go to your dashboard. Here you will see all existing CAPTCHAs and can create new CAPTCHAs.
2 – Choose existing CAPTCHA or create a new CAPTCHA
If you already have a CAPTCHA that you want to use, skip this step. If you don't have a CAPTCHA yet, create a new CAPTCHA now.Create a new CAPTCHADuring the creation process, select the “TrustCaptcha” product category and choose your preferred pricing plan. If you are not yet sure which pricing plan to choose, no problem! The plan can be extended at any time. Then decide whether you want to start with the 30-day trial version or go straight to a paid subscription. If you want to start directly with a paid CAPTCHA, all you have to do is add your billing details and optionally a payment method and you're ready to go.30-day trail periodIf you opt for the 30-day trial period, you can test CAPTCHA for 30 days risk-free. At the end of the 30-day trial period, CAPTCHA locks itself. During the 30-day trial period or up to 30 days after the end of the trial period, you can unsubscribe from CAPTCHA at any time for a fee or delete it with immediate effect. If you neither subscribe to the CAPTCHA for a fee nor delete it within 30 days of the end of the free trial period, it will be deleted automatically.Non-Commercial PlanIn addition to our standard plans, we also offer a permanently free “Non Commercial“ plan with 1 website and up to 500 free verifications for non-commercial websites and projects.
3 – Add your websites and check your credentials
On the dashboard of your CAPTCHA you will find all the important information, statistics and setting options. Here you will also find your site-key, the secret-key and, if available, the license-key. You will need these later on when integrating your CAPTCHA.Add your websitesYour CAPTCHA may only be accessed by websites that you explicitly authorise. To allow websites to access the CAPTCHA, enter all the websites on which you want to integrate the CAPTCHA in the settings.
4 – Solve the CAPTCHA in your frontend
Integrate the CAPTCHA widget into your website or app. You can find detailed instructions for the frontend integration in our documentation. The CAPTCHA widget will then be displayed on your website or app.
Prebuild frontend integrationsYou can use one of our pre-built integrations to integrate the CAPTCHA widget into your website or application. If there is no pre-built integration from us for your preferred frontend technology, your software developers can integrate the CAPTCHA themselves using our documentation or ask our support-team for a pre-built integration solution.
5 – Validate the CAPTCHA result in your backend
When the CAPTCHA has finished, take the verification token and send it to your backend. Then retrieve the verification result from our servers and determine your next steps. You can find detailed information on backend integration in our documentation.Basic steps for .NetThe basic steps for your .Net integration are as follows. For detailed instructions, please read our documentation.Install Dependency
Select a tab
Dotnet
Fetch Result
Select a tab
Fetch Result
Handle Result
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Handle Result
Other backend technology instead of .Net?If you do not want to use .Net or have several backend services you can select a different language or framework here. If there is no pre-built integration from us for your preferred backend technology, your software developers can integrate the CAPTCHA themselves using our documentation or ask our support-team for a pre-built integration solution.
6 – Congratulations 🎉
You are now protected by TrustCaptcha - congratulations!

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Frequently Asked Questions

What is a .NET CAPTCHA?

A .NET CAPTCHA is a security challenge you embed into ASP.NET or .NET Core forms and APIs to confirm that the visitor is human before your server processes the request. Unlike classic image puzzles, TrustCaptcha’s .NET integration runs automatically in the browser, then sends a signed token that you validate with just a few lines of C# code. Behind that simple flow, it layers dynamic proof-of-work, an AI-driven bot-score and customizable security policies to block advanced bots.

What is the best .NET CAPTCHA?

The best .NET CAPTCHA balances rock-solid bot defence with a friction-free user experience and full legal compliance. Pure proof-of-work services like CaptchaFox or FriendlyCaptcha slow attackers but cannot actively detect sophisticated headless bots, so their protection is limited. TrustCaptcha outperforms those options thanks to its multi-layered security stack and AI-driven bot score while remaining fully EU-hosted and GDPR-ready. Deep theming and white-label options further let you match your brand without extra CSS.

How does a .NET CAPTCHA work?

When the TrustCaptcha script loads, it starts a lightweight proof-of-work in the browser and collects anonymised behavioural signals. These signals are hashed into a signed token that your .NET backend verifies against the bot-score API, so no personal data ever leaves the EU. Developers simply read the token and call TrustCaptcha’s verification endpoint or .NET SDK, receiving a boolean and score within milliseconds.

Do I need a .NET CAPTCHA?

If your site exposes public forms, logins, search boxes or APIs, bots will eventually exploit them for spam, credential-stuffing or scraping. The 2025 threat landscape includes AI-driven headless browsers that bypass legacy image puzzles in seconds, so rate-limiting alone is no longer enough. Adding a multi-layered solution like TrustCaptcha stops both commodity and sophisticated attacks while staying invisible to genuine users.

Is TrustCaptcha GDPR-compliant and EU-hosted?

Yes—TrustCaptcha processes all CAPTCHA data exclusively in EU-based, ISO 27001-certified data centres and provides a standard Data Processing Agreement for every customer. It stores no cookies, encrypts all traffic and even offers an optional Minimal Data Mode for privacy-critical projects. That means you can deploy it without international data transfers or extra consent banners.

Can I customise the look and feel of TrustCaptcha?

TrustCaptcha supports more than 35 languages, light, dark or auto themes, full colour overrides and an invisible mode. You can also hide the branding, supply your own privacy-policy link and fine-tune size, border radius and autostart behaviour. These options help you maintain brand consistency and meet accessibility guidelines while still deterring bots.

Does TrustCaptcha impact performance or accessibility?

The TrustCaptcha script is up to three times lighter than image-heavy CAPTCHAs, improving load-time metrics and Core Web Vitals. Because it solves itself automatically and complies with WCAG 2.2, users with screen readers or motor impairments never face puzzle grids or timeouts. Client-side proof-of-work runs in the background and has negligible CPU impact on modern devices, providing strong security without hurting performance. That lean footprint aligns with Google’s Helpful Content guidance, which prioritises speed and accessibility when ranking support pages.