---
title: "For developers — Check Twice"
description: "Let your AI agent, shop or app verify anyone from their Check Twice link. One request tells you who made it, checked against their photo ID."
url: https://www.check-twice.com/developers
---

# Verify people without asking for their ID

One API call with their Check Twice link returns who they are.

```http
POST /v1/links/check
Authorization: Bearer ctk_…
Content-Type: application/json

{
  "link":
    "https://www.check-twice.com/l#…"
}
```

```http
HTTP/1.1 200 OK

{
  "name": "Olivia B.",
  "document_kind": "passport",
  "chip_verified": true
}
```

[Get started](https://www.check-twice.com/sign-in)

## Easy identity verification for your agent, shop or app

### Know exactly who you’re dealing with

Only accept links that show what you need, like a full name, a face photo or a chip-checked ID.

```ts
POST /v1/links/check

{
  "link": "https://www.check-twice.com/l#…",
  "require": {
    "full_name": true,
    "face_photo": true,
    "chip_verified": true
  }
}
```

[How to ask for details](https://www.check-twice.com/docs/check-a-link#ask-for-details)

### Make sure it’s still them

Only accept people who took a quick photo within a time frame you choose, like the last hour, day or six months.

```ts
POST /v1/links/check

{
  "link": "https://www.check-twice.com/l#…",
  "require": {
    "proved_within_seconds": 86400
  }
}
```

[How to ask for recent proof](https://www.check-twice.com/docs/check-a-link#ask-for-recent-proof)

## Common developer questions

### How do I get an API key?

Sign up to create a workspace on check-twice.com, then create API keys in your workspace.

### How much does it cost?

Nothing. It’s free, with tiers and rate limits in place to stop abuse.

### Do the people I check need Check Twice?

Yes. They make their link in the Check Twice app after proving who they are with a quick photo and their ID. It’s free for them too.

### How can I test it?

Make a link in the Check Twice app yourself and check it with your own key.

### What stops a link being reused?

Whoever makes a link can see each time it’s opened, and whether a person or a system opened it. They can also choose how many times it opens, from once to unlimited, so it can’t be reused.

### Can I tell if it’s the same person again?

Yes. Each check returns a code for the person who made the link. Their links always give you the same code, so you’ll know when it’s them again. Anyone else checking gets a different one.

### Can I keep what a check returns?

No. It must only be used to verify who they are, never stored, copied or shared.

### What if a link isn’t valid?

You get “link_not_valid” if it was deleted or never existed. Just ask them to generate a new one.

### How do I keep my key safe?

Keep it on your server, never in a browser or an app. If it’s ever exposed, delete it and make a new one.

## Let people prove it’s them with just a link

[Get started](https://www.check-twice.com/sign-in)

By [FusedFrames](https://fusedframes.com)