Email renderer for Node.js: compile JSON designs to MJML & HTML

1Install the SDK

Add the backend SDK to your Node service. It runs server-side and holds your secret server key.

npm install email-craft-sdk

2Render a design to MJML or HTML

Given a design (the JSON your users built in the editor, or one you store as a template), render it two ways: MJML for tooling that expects it, or ready-to-send email-safe HTML.

Rendering is a pure function, no client to construct, no secret key, no headless browser, and no network round-trip per element.

import { renderDesign, renderMjml } from "email-craft-sdk";

const design = await loadDesignFromYourDb(id);

const html = renderDesign(design, { fullDocument: true }); // inbox-safe HTML (inlined)
const mjml = renderMjml(design);                           // MJML markup

3Compile the MJML with mjml2html

If your pipeline already uses the mjml package, hand it the MJML from renderMjml and compile it with mjml2html as usual. The output is valid MJML: every starter template compiles with no validation errors in strict mode (checked with mjml 4.15.3).

You only need this step if you want MJML in the middle. renderDesign already returns inbox-safe HTML on its own.

import mjml2html from "mjml";
import { renderMjml } from "email-craft-sdk";

const { html, errors } = mjml2html(renderMjml(design), { validationLevel: "strict" });

4Personalize with merge tags

Pass merge tags at render time and they're substituted into the output, so each recipient gets a personalized email from a single design.

(Separately, the SDK's Mailkaro client, constructed with a secret sk_live_ key, resolves entitlements and handles asset uploads server-to-server, like firebase-admin. Pure rendering above needs none of that.)

const html = renderDesign(design, {
  fullDocument: true, mergeTags: { first_name: "Ada", order_id: "#1024" },
});

5Send with your provider

The rendered HTML is already inlined and table-based, so any ESP can send it as-is. Use MJML output instead if your pipeline compiles MJML downstream.

import { Resend } from "resend";
const resend = new Resend(process.env.RESEND_API_KEY);

await resend.emails.send({
  from: "you@yourapp.com", to: "customer@example.com", subject: "Your receipt", html, // from renderDesign(design, { fullDocument: true })
});