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PUT
/
templates
/
{slug}
curl --request PUT \
  --url https://app.lettr.com/api/templates/{slug} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "name": "Updated Welcome Email"
}
'
{
  "message": "Template updated successfully.",
  "data": {
    "id": 123,
    "name": "Updated Welcome Email",
    "slug": "welcome-email",
    "project_id": 5,
    "folder_id": 10,
    "active_version": 2,
    "merge_tags": [
      {
        "key": "NAME",
        "required": true
      }
    ],
    "created_at": "2026-01-15T10:00:00+00:00",
    "updated_at": "2026-01-28T14:30:00+00:00"
  }
}
Updates an existing template by its slug. You can update the template name, project assignment, or content. Providing new html or json content creates a new version of the template automatically. The html and json fields are mutually exclusive. If neither is provided, only metadata (name, project) is updated without creating a new version.

Authorizations

​
Authorization
string
header
required

API key for authentication

Path Parameters

​
slug
string
required

The template slug (URL-friendly identifier)

Example:

"welcome-email"

Body

application/json

Request to update an existing email template. All fields are optional - provide only what you want to change. If html or json is provided, a new active version will be created.

​
project_id
integer

Project ID to find the template in. If not provided, uses the team's default project.

Required range: x >= 1
Example:

5

​
name
string

New name for the template

Maximum string length: 255
Example:

"Updated Welcome Email"

​
html
string

New HTML content for the template. Creates a new active version. Mutually exclusive with json.

Example:

"<html><body><p>Hello {{NAME}}!</p></body></html>"

​
json
string

New JSON content for Topol visual editor templates. Creates a new active version. Mutually exclusive with html.

Example:

"{\"tagName\":\"mj-container\",\"children\":[{\"tagName\":\"mj-text\",\"content\":\"Hello {{FIRST_NAME}}!\"}]}"

Response

Template updated successfully

Response after successfully updating a template

​
message
string
required

Human-readable response message

Example:

"Template updated successfully."

​
data
object
required

View of an updated template