ALTCHA

Key features

• Silent proof-of-work challenge The browser proves itself computationally in the background, so legitimate visitors never see a puzzle while bots and form spam get filtered before submission.[1][2]

• No cookies, fingerprinting, or third-party sharing Verification runs without tracking visitors, which is the core of the product's GDPR-conscious positioning for EU-facing sites.[1][2]

• WCAG 2.2 AA conformant widget Keyboard navigation, screen-reader labels, and an audio option for interactive checks keep the challenge usable for visitors with disabilities.[1][2]

• 50-plus languages with automatic detection The widget localizes itself, including right-to-left language support, without per-language configuration.[1]

• Server libraries across ten ecosystems Official verification libraries cover TypeScript, PHP, Python, Go, Java, Rust, Ruby, Dart, Elixir, and C++, plus starters for React, Vue, Svelte, Solid, Lit, and Angular.[1][2]

• Adaptive escalation in Cloud and Sentinel Low-risk traffic passes silently while elevated-risk traffic faces an interactive check, backed by risk scoring and threat intelligence.[1][2]

• Self-hosted verification on your infrastructure Challenge generation and checking run on the operator's own server via npm, CDN script tag, Docker, Kubernetes, AWS, or Azure installs, with offline license verification for Sentinel.[1][2]

• WordPress coverage without code The plugin protects logins, comments, and more than 22 form plugins, with a Professional tier for advanced needs.[1][2]

Who will love it

• Teams replacing image puzzles with silent verification remove the abandonment and frustration of puzzle CAPTCHAs on logins, sign-ups, and checkout forms.[1][2]

• Self-hosted verification with EU-built provenance fits GDPR-conscious organizations that cannot send traffic data to a foreign CAPTCHA vendor.[1][2][3]

• One plugin spans logins, comments, and dozens of form integrations on WordPress without custom development work.[1][2]

Who should avoid it

• The core requires building a challenge endpoint and verifying submissions with a library; only the managed Cloud edition removes that operational burden.[1][2]

• With no Reddit or G2 reports found in this pass and adoption figures limited to the vendor's own 300000-sites claim, there is little third-party confirmation of day-to-day behavior under attack.[1]

• Single sign-on is scoped to Sentinel Enterprise, and human support beyond basic email is a paid add-on, so small-plan buyers should budget accordingly.[1]

Alternatives and compatibility