---
title: MetaExpression type | Wartiva GraphQL API
description: MetaExpression represents an nftables expression for accessing meta-data about the packet, the network device, or the system context.
url: https://wartiva.com/api-docs/types/meta-expression.html
updated: 2026-10-07
---

Endpoint configuration · GraphQL type

# `MetaExpression` type

MetaExpression represents an nftables expression for accessing meta-data about the packet, the network device, or the system context.

## Fields

| Field Name | Description |
|---|---|
| `key` - [`NftMetaKey!`](https://wartiva.com/api-docs/types/nft-meta-key.html) | The specific meta-data key to access (e.g., packet length, interface name, connection mark). |
| `sourceRegister` - [`Boolean!`](https://wartiva.com/api-docs/types/boolean.html) | If true, the 'register' field is used as a source register for the meta-data operation. If false, 'register' is used as a destination register for storing the meta-data. |
| `register` - [`NftRegister!`](https://wartiva.com/api-docs/types/nft-register.html) | The register used to either store the retrieved meta-data (if 'sourceRegister' is false) or to provide input for a meta-data operation (if 'sourceRegister' is true). |

## Used by

- [`ChainExpression`](https://wartiva.com/api-docs/types/chain-expression.html) union: A union of all possible nftables chain expression types.

## Example

### Example

```json
{"key": "LEN", "sourceRegister": true, "register": "VERDICT"}

```

---

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