The rendering linter for email
Quick Start · What It Catches · Why Emailens · Supported Clients · API Docs
Your email looks perfect in Apple Mail. Gmail strips half the CSS. Outlook renders it in Word.
@emailens/engine analyzes HTML, React Email, MJML, and Maizzle against 21 email clients and scores compatibility before your email goes out. It catches the issues in the engine, in the terminal, in CI, and inside AI coding workflows.
If you want the fastest path to trying it locally, start with the CLI:
npx @emailens/cli lint email.html
The CLI is the recommended entry point for open-source usage. The engine is the lower-level library for builders, tools, and custom integrations.
emailens.dev is the hosted SaaS for shared previews, screenshots, visual diffs, and team workflows. The open-source packages are the local developer tooling.
Quick Start
Option 1: Try the CLI first
npx @emailens/cli lint email.html
Option 2: Use the engine as a library
npm install @emailens/engine
import { auditEmail } from "@emailens/engine";
const html = `<html><body><div style="display:flex; gap: 12px;">...</div></body></html>`;
const report = auditEmail(html, { framework: "jsx" });
console.log(report.compatibility.scores["outlook-windows"]);
The main entry runs in the browser as well as in Node, and a test keeps it that
way. The Node-only parts live in subpaths: @emailens/engine/compile (React
Email, MJML and Maizzle compilers) and @emailens/engine/server (DNS and
SpamAssassin checks).
What It Catches
- CSS compatibility across 21 clients
- Spam scoring and content hygiene signals
- Accessibility checks for contrast and semantics
- Image and link validation
- Inbox preview and client-specific rendering issues
- Template variable and overflow problems
- AI fix generation for structural issues
Every finding may include source positions, so a result can be pointed at, annotated, or fixed in place.
Why Emailens?
- Offline-first: runs locally with no account required
- Unified audit: a single tool checks CSS, spam, accessibility, links, images, and more
- Framework-aware: works with raw HTML, React Email, MJML, and Maizzle
- AI-ready: structural fixes can be generated with any model provider
- Programmable: use it in CI, editors, scripts, or custom tooling
Supported Email Clients
Each client links to its support page on emailens.dev, built from this package's data. Every feature across all 21 clients: emailens.dev/email-css.
Ecosystem
License
MIT, Copyright 2025 Emailens
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