User-friendly and GDPR-compliant CAPTCHA for Java Servlet made in EU: privacy-first and easy to integrate
Start free trial3 easy steps
A Private Captcha account is needed to issue CAPTCHA challenges and to verify their solutions. Inside you can register a new domain and create an API key. Check out everything for free during 14 days without a credit card.
Getting started guideTo enable protection, you need to add our widget to your website page or form and disable form submit until CAPTCHA is solved. Works with native HTML as well as React and Vue. Widget is easy to install and customize.
Check docsYou need to verify CAPTCHA solution before form submission is processed in the backend. Install our library for Java Servlet (batteries included) and check out the copy-and-paste snippets for your backend code.
Check docs
import com.privatecaptcha.*;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.*;
import java.io.IOException;
@WebServlet("/submit")
public class FormServlet extends HttpServlet {
private final PrivateCaptchaClient client = new PrivateCaptchaClient(
new PrivateCaptchaConfiguration("YOUR_API_KEY")
);
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws IOException {
try {
VerifyOutput output = client.verifyRequest(request::getParameter, "YOUR_SITEKEY");
if (!output.ok()) {
response.sendError(403, "Captcha verification failed");
return;
}
} catch (Exception e) {
response.sendError(403, "Captcha verification failed");
return;
}
// Verification passed. Process your form submission here.
response.getWriter().println("Success!");
}
}
Backend
Add the official library to your project:
// build.gradle
implementation 'com.privatecaptcha:private-captcha-java:0.0.1'Initialize a client with your API key and Sitekey. Keep the API key as your server secret.
Verify the private-captcha-solution form field before running any business logic. Continue only when verification passes.
Frontend
Load the deferred script directly from our CDN. The widget adds the solution to your form automatically, ready for backend verification.
Place the widget inside your form and replace YOUR_SITE_KEY with your property's sitekey from the Portal.
Keep the submit button disabled. Set data-finished-callback to a function that enables it once the captcha is solved.
<script defer
src="https://cdn.privatecaptcha.com/widget/js/privatecaptcha.js">
</script>
<form action="/submit" method="POST">
<!-- Your form fields go here. -->
<div class="private-captcha"
data-sitekey="YOUR_SITE_KEY"
data-finished-callback="onCaptchaSolved"></div>
<button id="formSubmit" type="submit" disabled>Submit</button>
</form>
<script>
function onCaptchaSolved() {
document.querySelector("#formSubmit").disabled = false;
}
</script>After implementing the basics, here's what else you can do.
Customize CAPTCHA puzzle difficulty for your unique use-case
Different visual themes, more than 10 localizations, popup/hidden modes and more
Protect the whole website from AI scrapers and bots
Question zone
Instead of asking users to solve complex puzzles or track their behavior, Private Captcha solves an invisible cryptographic task in the background. The system automatically adjusts the task difficulty, ensuring smooth access for real users while making it too costly for bots to attempt. Cryptographic task provides equal security regardless of bot's intelligence level, making it effective even as AI technology improves. Which is hard to say about image/sound recognition tasks of other captchas.
On scale, bots exhibit different usage patterns and fingerprints statistics than real users. Detection of those patterns is part of the Private Captcha solution as we process a lot of request data on behalf of our clients.
No. Scraping protection issues a signed cookie with validity period that you configure in the dashboard. During that period all requests do not incur additional API calls.
Unlike other solutions, that only have client-side code open, Private Captcha's backend code is also publicly available, making it easy to verify how user data is handled. Additionally, you can host Private Captcha on premises inside your own organization.
Private Captcha comes with many pre-built integrations for popular online platforms, such as WordPress, and packages for many popular programming languages (Javascript, Python, etc.). Additionally, our documentation provides detailed setup and migration guides and integration examples.
The Private Captcha widget offers two color themes (light and dark) and also allows to do lower-level customization, using CSS, ensuring seamless integration with your website. Additionally, you can hide the captcha widget altogether and make your custom UI integration, all while keeping security benefits.
Independent, privacy-first, user-friendly CAPTCHA service made in EU