> ## Documentation Index
> Fetch the complete documentation index at: https://docs.qedproof.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Trust levels

> What a checker can actually confirm about a receipt, from a signature alone up to a hardware- or web-proven observation.

export const NotBuilt = ({what}) => <Note>{what ? `${what} is not built yet.` : "This is not built yet."} It's described here so you know what to expect, not as something you can use today.</Note>;

Every receipt carries a `trust_level` from 1 to 4. It's the issuer's claim about which guarantees it provides — a
checker should always compute the level it can actually confirm ("achieved" trust level) and report the lower of
the two.

| Level | Name       | The issuer additionally provides                 | A checker can confirm                                                                          |
| ----- | ---------- | ------------------------------------------------ | ---------------------------------------------------------------------------------------------- |
| 1     | Signed     | The Ed25519 signature over the receipt body      | The issuer stated this, and it hasn't been altered                                             |
| 2     | Anchored   | A Merkle inclusion proof and an on-chain anchor  | ...and it existed no later than the anchor time. It can't be backdated or silently deleted     |
| 3     | Attested   | An `attestation` plus the verifier's `code_hash` | ...and a specific, published verifier build produced the observation inside a hardware enclave |
| 4     | Web-proven | A zero-knowledge TLS proof inside `attestation`  | ...and the facts came from the destination's TLS session, without trusting hardware            |

## Status today

* **Level 1 (Signed)** and **level 2 (Anchored)** are implemented. Anchoring currently runs on Base Sepolia — see
  [anchoring](/concepts/anchoring).
* **Levels 3 (Attested) and 4 (Web-proven)** are specified in the protocol but not implemented.

<NotBuilt what="Trust levels 3 and 4" />

## Why a checker recomputes the level

`trust_level` in a receipt's body is only what the issuer claims. A checker that verifies a receipt should
independently confirm inclusion and the anchor before reporting level 2, and should never present a higher level than
what actually verified. This is why [checking a receipt yourself](/concepts/check-a-receipt) reports an "achieved"
trust level alongside the verdict.