> ## Documentation Index
> Fetch the complete documentation index at: https://tfh-codex-yc-world-id-guide.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# World ID for YC Startups

> Simple ways to build trust into your startup with World ID.

The World stack is a privacy-preserving trust layer for companies that need to know whether a real, unique, present, or eligible person is behind an action.

## Start with the trust question you need to answer

| Question                    | Use                       | What it helps you do                                                                                                      |
| --------------------------- | ------------------------- | ------------------------------------------------------------------------------------------------------------------------- |
| Who can participate?        | **World ID**              | Prove a user is a real, unique human.                                                                                     |
| Who is present right now?   | **Selfie Check**          | Confirm that a human is approving an important action.                                                                    |
| Who meets the requirements? | **Identity Attestations** | Verify an attribute such as age, nationality, residency, or document validity without collecting the underlying document. |
| When can an agent act?      | **AgentKit**              | Let an AI agent act after the required human trust checks are satisfied.                                                  |

## Why startups use World ID

1. **Stop bots and duplicate accounts.** Make rewards, referrals, voting, reviews, promotions, and social participation one-person-one-action.
2. **Protect sensitive moments.** Add human presence when someone approves a payment, recovers an account, deploys software, or authorizes a high-risk transaction.
3. **Check eligibility privately.** Confirm that someone meets a policy without asking your product to store their full identity documents.
4. **Match trust to risk.** Start with a lightweight check, then require stronger proof of humanity, presence, or eligibility where the stakes are higher.
5. **Build safer AI products.** Distinguish people from agents and make human approval an explicit boundary for consequential actions.
6. **Make communities more accountable.** Reduce impersonation, fake accounts, reputation manipulation, and fraudulent content while preserving privacy.

## Where it fits in YC startups

| If you're building...                      | The simplest place to use World ID                                                                 |
| ------------------------------------------ | -------------------------------------------------------------------------------------------------- |
| Proving you're human                       | Require one human per account to reduce Sybil attacks.                                             |
| An AI consumer product                     | Protect a free trial, referral, reward, or limited promotion from duplicate claims.                |
| Multiplayer AI                             | Distinguish verified people from AI agents in a shared environment.                                |
| An operating system for the physical world | Make sure tasks are assigned to real, unique workers.                                              |
| A real-world data product                  | Limit data contribution and rewards to one unique contributor.                                     |
| AI-native compliance                       | Add a privacy-preserving proof that a user is a real human before a regulated or high-risk action. |
| Crypto or stablecoins                      | Run fair allocations, grants, governance, airdrops, or incentives.                                 |
| Cloud tools for small software             | Reduce fake workspaces, spam, and abuse before privileged access.                                  |
| Education                                  | Protect scholarships, subsidized access, rewards, and student benefits.                            |
| Products for the aging population          | Reduce impersonation of patients, family members, and caregivers.                                  |
| Self-maintaining APIs                      | Add human accountability before critical code changes, merges, or deployments.                     |
| Defense or physical infrastructure         | Add a human trust signal to safety-critical operations.                                            |

## Keep the first use case simple

Choose the one action where abuse would most change the outcome—such as creating an account, claiming a reward, receiving a referral benefit, voting, or accessing a scarce resource. Start there, then add stronger trust signals only when the risk calls for them.

<Note>
  World ID helps you know that a unique human can participate. Use Selfie Check when you need a signal that someone is present now, Identity Attestations when you need to know whether they meet a requirement, and AgentKit when an agent needs to act on their behalf.
</Note>

## Ready to build?

[Start integrating World ID](/world-id/idkit/integrate) to bring the right trust signal into your product.