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wtf is altcha?

andersk/altcha — explained in plain English

Analysis updated 2026-07-18 · repo last pushed 2025-06-03

Audience · developerComplexity · 3/5StaleSetup · moderate

TL;DR

ALTCHA is a self-hosted, privacy-first spam and bot protection widget that uses an invisible proof-of-work puzzle instead of tracking cookies or visual CAPTCHAs.

Mindmap

mindmap
  root((ALTCHA))
    What it does
      Proof-of-work challenge
      Blocks spam and bots
      No tracking or cookies
    Tech Stack
      JavaScript widget
      TypeScript backend
      Python PHP Go Java Ruby Elixir
    Use Cases
      Signup form protection
      Donation form spam block
      API abuse prevention
    Audience
      Web developers
      Privacy conscious teams
    Features
      GDPR CCPA compliant
      WCAG accessible
      Lightweight 29KB

Code map

Detail Auto

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filefunction / class

Why would anyone build with this?

REASON 1

Replace a third-party CAPTCHA on a signup or contact form with a privacy-friendly, cookie-free alternative.

REASON 2

Add adaptive spam filtering to an API or donation form using ALTCHA Sentinel.

REASON 3

Protect a React, Vue, Svelte, or Angular app from bots using a ready-made starter template.

What's in the stack?

JavaScriptTypeScriptPythonPHPGoJavaRubyElixir

How it stacks up

andersk/altcha0verflowme/alarm-clock0verflowme/seclists
Language—CSS—
Last pushed2025-06-032022-10-032020-05-03
MaintenanceStaleDormantDormant
Setup difficultymoderateeasyeasy
Complexity3/52/51/5
Audiencedevelopervibe coderops devops

Figures from each repo's GitHub metadata at analysis time.

How do you spin it up?

Difficulty · moderate Time to first run · 30min

Requires running your own backend verification server and embedding the widget script.

The explanation does not specify the license terms.

Yoink these prompts

Prompt 1
Show me how to add the ALTCHA widget to a signup form in my React app so it verifies submissions without cookies.
Prompt 2
How do I set up an ALTCHA backend verification server using one of the TypeScript or Python libraries?
Prompt 3
Explain how ALTCHA's proof-of-work challenge works and why it doesn't need to track or fingerprint users.
Prompt 4
Help me add an accessible ALTCHA code-challenge fallback with audio playback to my form.

Frequently asked questions

wtf is altcha?

ALTCHA is a self-hosted, privacy-first spam and bot protection widget that uses an invisible proof-of-work puzzle instead of tracking cookies or visual CAPTCHAs.

Is altcha actively maintained?

Stale — no commits in 1-2 years (last push 2025-06-03).

What license does altcha use?

The explanation does not specify the license terms.

How hard is altcha to set up?

Setup difficulty is rated moderate, with roughly 30min to a first successful run.

Who is altcha for?

Mainly developer.

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