API Reference

Update template

PATCH /templates/:id — edit a template's name, subject, or body.

PATCH/templates/:id

Updates only the fields you provide; omitted fields are left unchanged.

Body parameters

namestringoptional

New name.

aliasstring | nulloptional

New alias. Pass null to clear. Must be unique across your templates.

subjectstring | nulloptional

New default subject. Pass null to clear.

htmlstring | nulloptional

New HTML body. Pass null to clear.

textstring | nulloptional

New plain-text body. Pass null to clear.

fromstring | nulloptional

New default sender address. Use "Your Name <sender@domain.com>" for a friendly name. Pass null to clear.

reply_tostring | string[] | nulloptional

New default Reply-To address, or an array of addresses (an array is stored and returned as a single comma-separated string). Pass null to clear.

variablesarrayoptional

Replaces the template's variables (up to 50). Each is an object with key, type, and optional fallback_value — same shape as on create.

variables[] object

keystringrequired

The variable key. Reserved names that cannot be used: FIRST_NAME, LAST_NAME, EMAIL, UNSUBSCRIBE_URL, contact, this. Keys must start with a letter or underscore and contain only letters, digits, underscores, or dots.

type'string' | 'number'optional

The type of the variable. Defaults to string when omitted.

fallback_valuestring | number | nulloptional

The value used when none is supplied at send time. Must match type.

import { Mailblastr } from 'mailblastr';

const mb = new Mailblastr('mb_xxxxxxxxx');

const { data, error } = await mb.templates.update('43f68331-0622-4e15-8202-246a0388854b', { "subject": "Welcome aboard, {{first_name}}!" });
console.log({ data, error });

Also edits a draft (does not auto-publish). Returns { object: "template", id }. A published template keeps serving its last published snapshot until you publish again.

Field limits

These caps are enforced at the API boundary. Exceeding one returns a validation_error naming the field, e.g. *subject must be 998 characters or fewer.*

Field	Maximum length
`name`	255
`subject`	998
`from`	320
`reply_to`	320
`alias`	255

Errors: not_found if no template with that id (or alias) belongs to you; validation_error if a field exceeds its maximum length, if the new alias is already used by another of your templates, or if variables is invalid (not an array, more than 50 entries, reserved/duplicate/invalid key, unknown type, or a fallback_value that does not match its type). See Errors.