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Open Source Application Security Tools

A curated collection of the best open source tools for securing software applications during development and runtime..

See also:CAPTCHA & Bot ProtectionFeature Flags

Unleash

Feature flags for rapid, risk-free software deployment

  • Stars

    13,934

  • Last commit

    23 hours ago

  • License

    AGPL-3.0
A powerful feature management platform enabling gradual rollouts, A/B testing, and seamless integration for continuous delivery.

Open Source Alternative to:

LaunchDarkly

Cap

Privacy-first CAPTCHA alternative with proof-of-work

  • Stars

    Stars growing over the last 30 days8,254

  • Last commit

    7 days ago

  • License

    Apache-2.0
Lightweight open-source CAPTCHA solution using SHA-256 proof-of-work. 250x smaller than hCaptcha, fully customizable, and privacy-focused with zero telemetry.

Open Source Alternative to:

reCAPTCHA

GrowthBook

Open-source A/B testing and feature flagging platform

  • Stars

    8,566

  • Last commit

    13 hours ago

  • License

    MIT
Powerful, developer-friendly experimentation tool for data-driven product decisions. Seamless integration, real-time insights, and flexible deployment.

Open Source Alternative to:

LaunchDarkly

Flagsmith

Feature flags and remote config for rapid deployment

  • Stars

    6,640

  • Last commit

    15 hours ago

  • License

    BSD-3-Clause
Powerful feature management platform for seamless software releases, A/B testing, and personalized user experiences.

Open Source Alternative to:

LaunchDarkly

Flipt

Git-native feature management for developers

  • Stars

    4,938

  • Last commit

    13 hours ago

  • License

    GPL-3.0
A feature flag platform that integrates with Git workflows, enabling developers to manage features directly in their codebase.

Open Source Alternative to:

LaunchDarkly

ALTCHA

Next-Gen CAPTCHA and Spam Protection, GDPR compliant

  • Stars

    2,877

  • Last commit

    14 days ago

  • License

    MIT
ALTCHA offers cutting-edge spam and abuse protection for websites and apps, with privacy-friendly CAPTCHA alternatives designed for GDPR compliance.

Open Source Alternative to:

reCAPTCHA

FeatBit

Open-source feature flag management for seamless deployments

  • Stars

    1,953

  • Last commit

    9 hours ago

  • License

    MIT
FeatBit is a fast, scalable feature flag service that enables risk mitigation and fosters business growth through controlled feature releases.

Open Source Alternative to:

LaunchDarkly

mCaptcha

Privacy-first proof-of-work CAPTCHA without user friction

  • Stars

    2,499

  • Last commit

    1 year ago

  • License

    AGPL-3.0
Privacy-focused proof-of-work CAPTCHA system that silently protects websites without tracking users or requiring image solving. Drop-in replacement for reCAPTCHA.

Open Source Alternative to:

reCAPTCHA

Featurevisor

Feature management with GitOps for developers

  • Stars

    814

  • Last commit

    17 hours ago

  • License

    MIT
Featurevisor is an open-source tool for managing feature flags, experiments, and remote configuration directly from your Git repository.

Open Source Alternative to:

LaunchDarkly

Procaptcha

Decentralized CAPTCHA for enhanced web security

  • Stars

    303

  • Last commit

    17 hours ago

  • License

    Apache-2.0
A blockchain-based CAPTCHA solution offering improved security, user experience, and resistance to bot attacks for web applications.

Open Source Alternative to:

reCAPTCHA

Private Captcha

GDPR-compliant bot protection without user friction

  • Stars

    199

  • Last commit

    1 day ago

  • License

    Unknown
Privacy-first CAPTCHA service that blocks bots while keeping forms accessible. No puzzles, no tracking, no cookies - just invisible cryptographic protection.

Open Source Alternative to:

reCAPTCHA

Abby

Type-safe feature flags and remote config for developers

  • Stars

    167

  • Last commit

    1 year ago

  • License

    AGPL-3.0
Abby offers open-source, fully typed feature flagging and remote configuration for React and Next.js, with multi-environment testing and debugging tools.

Open Source Alternative to:

LaunchDarkly

Friendly Captcha

Invisible bot protection that respects user privacy

  • Stars

    37

  • Last commit

    3 days ago

  • License

    MPL-2.0
Privacy-compliant CAPTCHA alternative using proof-of-work technology. Protects websites from bots and spam without user interaction or data tracking.

Open Source Alternative to:

reCAPTCHA

OneHuman

Access control for AI agents your customers log in with

  • Stars

    23

  • Last commit

    2 days ago

  • License

    BUSL-1.1
Detects AI agents using customer credentials, masks private fields, holds risky actions for passkey approval, and signs every decision on your own server.

Open Source Alternative to:

HUMAN Security
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