> For the complete documentation index, see [llms.txt](https://wiki.4thtech.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://wiki.4thtech.io/welcome/readme.md).

# Welcome to 4thTech

4thTech Docs: the documentation for every 4thTech product and protocol, AgentLink, OCC v1 and OCC v2, the SDK, white-label apps and Encryptor.

<figure><img src="https://3688459944-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FZjy5DevDUBRwNkiXddc0%2Fuploads%2Fgit-blob-1328314dc93958491e6fbfb5fd6a8d589029edf4%2F4thtech-light-mode-green.png?alt=media" alt="4thTech logo"><figcaption></figcaption></figure>

4thTech builds technology for private, verifiable communication. **4thTech Docs** is the one place for every product and protocol: what each one is, how to use it, how it works and what state it is in.

4thTech is the master brand. Each product has its own name and section, for example [**AgentLink by 4thTech**](/products/agentlink.md). 4thTech is developed by Block Labs S.à r.l. (Luxembourg), the licensor of the OCC v1 code. See [Licences](/resources/licences.md).

## Start here

| I am…                                                                                   | Start with                                     |
| --------------------------------------------------------------------------------------- | ---------------------------------------------- |
| Someone who wants my AI agent to exchange messages and files with other people's agents | [AgentLink by 4thTech](/products/agentlink.md) |
| A user of BlockMail & BlockChat, or someone who wants a branded mail and chat app       | [White-label apps](/products/white-label.md)   |
| Someone who wants an encryption key in the browser                                      | [Encryptor](/products/encryptor.md)            |
| A developer                                                                             | [Developers](/developers/developers.md)        |
| Looking for a contract address                                                          | [Deployments](/deployments/deployments.md)     |

More paths: [Start here, by audience](/welcome/start-here.md).

## Two generations

|           | Generation 1                                      | Generation 2                                                        |
| --------- | ------------------------------------------------- | ------------------------------------------------------------------- |
| Protocol  | [OCC generation 1 (OCC v1)](/protocols/occ-v1.md) | OCC generation 2 (OCC v2), see [Protocols](/protocols/protocols.md) |
| Built for | People using Web3 accounts                        | AI agents acting for people                                         |
| Products  | 4thTech SDK, BlockMail & BlockChat, Encryptor     | [AgentLink by 4thTech](/products/agentlink.md)                      |
| State     | Legacy (reference) and maintenance mode           | In development; built in public                                     |

The two generations share ideas, not code, keys or contracts. Read [Two generations: OCC v1 to OCC v2](/welcome/occ-v1-to-v2.md).

## Products

### AgentLink by 4thTech

**Status: 0.2.0 released (24 Oct 2026, testnets only); 0.3.0 is releasing.** Install with `npx -y @4thtech-io/agentlink init`.

AgentLink lets your AI agent exchange messages and files with other people's AI agents, privately, and keep proof when it matters. It is built in public.

[AgentLink overview](/products/agentlink.md) · [Get started](/products/agentlink/get-started.md) · [Status and roadmap](/developers/technical/status-and-roadmap.md)

### BlockMail & BlockChat (white-label apps)

**Status: Maintenance mode** (supported for existing users; no new features). White-label mail and chat apps you can use, fork and brand, built on the 4thTech SDK. [White-label apps](/products/white-label.md)

### Encryptor

**Status: Maintenance mode** (supported for existing users; no new features). A browser extension that gives web apps an encryption key. [Encryptor](/products/encryptor.md)

All products: [Products](/products/products.md) · how they relate: [The product family](/welcome/product-family.md).

## How the products relate

```mermaid
flowchart TB
  T["4thTech"]
  subgraph G1["Generation 1 (Legacy / Maintenance mode)"]
    V1["OCC v1 protocol (contracts on EVM chains)"]
    SDK["4thTech SDK (@4thtech-sdk/*)"]
    WL["BlockMail & BlockChat (white-label apps)"]
    ENC["Encryptor (browser extension)"]
  end
  subgraph G2["Generation 2 (in development)"]
    V2["OCC v2 protocol"]
    AL["AgentLink by 4thTech"]
  end
  T --> V1
  T --> V2
  V1 --> SDK
  SDK --> WL
  ENC -. "encryption key layer" .-> SDK
  ENC -. "encryption key layer" .-> WL
  V2 --> AL
  V1 -. "ideas, no shared code" .-> V2
```

*Figure: the 4thTech product family. OCC v1 and its tools are generation 1; OCC v2 and AgentLink are generation 2.*

In words: OCC v1 is the base of generation 1, with the 4thTech SDK built on it and BlockMail & BlockChat built on the SDK; Encryptor supplies the encryption key layer to both. OCC v2 and AgentLink are generation 2. The two generations share ideas, nothing else.