# E04046 — EmailTemplateSlugInvalid

This is not a valid slug.

- **HTTP status**: `422`
- **Type**: `validation_error`
- **Name**: `EmailTemplateSlugInvalid`

## What to do

A slug can contain lowercase letters, numbers, hyphens and underscores. It has to start and end with a letter or a number, and it can be up to 63 characters long. Pick it carefully, because a slug cannot be changed after the template is created. The display name has no such rules and you can change it whenever you like.

## Related

- [E04xxx — Email sending & delivery](/docs/api/errors/E04xxx): every code in this range
- [Errors](/docs/api/errors): the full wire contract, status mapping, and error catalog
- [Error handling](/docs/guides/errors): branching on `type` and `code`, validation details, and `vendor_code`

## Related resources

- [Should I use a Bird SDK or call the API directly?](/explained/platform/should-i-use-an-sdk-or-call-the-api-directly) (answer)
- [Build your first integration](/learn/paths/integration) (course)
- [Send your first email](/docs/get-started/send-your-first-email) (docs)

[Get an implementation brief](/learn/workspace?topic=api-basics)