PrivateCaptcha/README.md

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Private Captcha is an independent, privacy-first, self-hostable Proof-of-Work CAPTCHA service made in EU.

## About

### Project goals

- provide powerful means to fight bots, including AI scrapers, and spam even as AI improves
- make web a slightly better place by replacing existing frustrating CAPTCHAs
- stay focused on privacy and GDPR compliance as well as on-prem deployment
- provide stable, backward-compatible and reliable API and integrations
- be sustainable financially to fulfill previous goals long enough

### Features

- adaptive challenge difficulty (including various configuration options)
- optimized backend (low resource requirements)
- lightweight, customizable widget (including "invisible" version)
- usage statistics (backend)
- privacy-focused, no behavior tracking or PII processing

## Documentation

Please refer to the [official documentation](https://docs.privatecaptcha.com).

### Getting started

To spin up a local version of Private Captcha _for development_, clone this repository and run `make run-docker` in the root (it requires to have Docker installed). You can check [Makefile](./Makefile) for details of what it does exactly.

### OpenAPI / Swagger

OpenAPI spec is [available](./docs/openapi.yaml).

### Project structure

```
├── cmd/                              Main executable of the server and few helpers
├── docker/                           Development-only docker files
├── docs/                             Developer documentation snippets
├── Makefile
├── pkg/                              Backend part of the project (API and Portal)
├── web/                              Frontend part of the project (Portal)
└── widget/                           Client-side widget code
```

### Built with

- _Go_ for backend (API and Portal)
- _JavaScript_ (inevitably) for client widget, including WASM workers (where possible)
- _Postgres_ for "business" data (accounts, properties etc.)
- _ClickHouse_ for "operational" data (difficulty scaling, statistics etc.)
- TailwindCSS for Portal (backend)

### Self-hosting

Self-hosting setup is in [another repository](https://github.com/PrivateCaptcha/self-hosting) and documentation - on main docs website.

## Alternatives

Private Captcha is a private and open alternative to:

- [Google reCAPTCHA](https://www.google.com/recaptcha/about/)
- [hCaptcha](https://www.hcaptcha.com/)
- [CloudFlare Turnstile](https://developers.cloudflare.com/turnstile/)

### Comparisons

> DISCLAIMER: just like other similar tables, this reflects an author's opinion more than "legal reality"

Feature | Private Captcha | Friendly Captcha | Cap | Altcha | CloudFlare Turnstile | Google reCAPTCHA | hCAPTCHA
--- | --- | --- | --- | --- | --- | --- | ---
User-friendly | :white_check_mark: | :white_check_mark: | :white_check_mark: | :white_check_mark: | :white_check_mark: | :x: | :x:
GDPR-compliant | :white_check_mark: | :white_check_mark: | :white_check_mark: | :white_check_mark: | :yellow_circle: | :yellow_circle:* | :yellow_circle:*
Self-hostable | :white_check_mark: | :yellow_circle:* | :white_check_mark: | :white_check_mark: | :x: | :x: | :x:
Difficulty scaling | :white_check_mark: | :white_check_mark: | :yellow_circle: | :white_check_mark: | :white_check_mark: | :yellow_circle: | :yellow_circle:
High-throughput* | :white_check_mark: | :white_check_mark: | :x: | :x: | :white_check_mark: | :yellow_circle: | :yellow_circle:
Sustainable* | :white_check_mark: | :white_check_mark: | :x: | :white_check_mark: | :white_check_mark: | :white_check_mark: | :white_check_mark:

> NOTE: Friendly Captcha actually offers some kind of abandoned PHP implementation of static (no scaling) difficulty puzzles, but it's obviously unusable in real production

> NOTE: "High-throughput" means low-latency backend (e.g. no Javascript on the backend, like in Cap and Altcha), profiled and optimized

> NOTE: "Sustainable" means this project has means to survive (which, for example, in Google/CloudFlare case is "indefinitely" due to other kinds of revenue). Private Captcha, Altcha have a managed/SaaS offering that is fueling the development.

> NOTE: reCAPTCHA and hCAPTCHA both self-declare to be GDPR-compliant, but since there was no court precedent to prove otherwise at the time of writing, they both collect excessive amounts of user tracking data.

## License

This project is distributed under a PolyForm Noncommercial License (see [LICENSE](./LICENSE) for more information). This allows you to self-host community edition of Private Captcha for non-commercial use. Commercial licenses available for enterprise edition - please contact us at hello@privatecaptcha.com

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