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

> Source Substrate runtime metadata via types bundles — handle runtime upgrades, custom pallet types, and deprecated metadata format gracefully.

# Substrate types bundles

### Where do I get a types bundle for my chain?

Types bundle is only needed for pre-Metadata v14 blocks and only if SQD does not offer a built-in support for the chain in question.

Most chains publish their type bundles as an npm package (for example: [Edgeware](https://www.npmjs.com/package/@edgeware/node-types)). One of the best places to check for the latest version is the [polkadot-js/app](https://github.com/polkadot-js/apps/tree/master/packages/apps-config/src/api/spec) and [polkadot-js/api](https://github.com/polkadot-js/api/tree/master/packages/types-known/src/spec) repositories.

<Note>
  The type bundle format for typegen is slightly different from `OverrideBundleDefinition` of `polkadot.js`. The structure is as follows, all the fields are optional.
</Note>

```javascript theme={"system"}
{
  types: {}, // top-level type definitions, as `.types` option of `ApiPromise`
  typesAlias: {}, // top-level type aliases, as `.typesAlias` option of `ApiPromise`
  versions: [ // spec version specific overrides, same as `OverrideBundleDefinition.types` of `polkadot.js`
    {
       minmax: [0, 1010] // spec range
       types: {}, // type overrides for the spec range
       typesAlias: {}, // type alias overrides for the spec range
    }
  ]
}
```