Build, lint, and ship flawless HTML emails in every inbox.
EMLinter is the free, browser-based toolkit email developers actually use. Validate HTML, simulate dark mode, generate bulletproof Outlook code, and edit templates visually — all without a signup.
Everything you need to build email — in one place
A focused toolkit that replaces three subscriptions. Lint, minify, preview, generate, and edit — without leaving the browser.
HTML Email Linter
Catch unclosed tags, broken nesting, and Outlook-specific bugs the second you paste your code.
Validate codeNo-Code Visual Editor
Let marketing teams edit text, swap images, and update links on coded templates — without touching HTML.
Open editorTemplate Library
Free, fully responsive HTML email templates you can edit, export, and drop into any ESP.
Browse templatesBulletproof Outlook Tools
Generate VML buttons and background images that render in every Microsoft Outlook version.
Open Outlook kitDark Mode Tester
Simulate Outlook and Gmail dark modes side-by-side and flag low-contrast text automatically.
Test dark modeBeautify + Minify
Format messy code for debugging, then minify the final build to slip under Gmail's 102KB clip.
Optimize codeThe four-step EMLinter workflow
From blank canvas to send — without context-switching between Litmus, Stripo, and a manual VML cheat sheet.
Build or paste
Start from a free template, paste your existing HTML, or open the no-code Visual Editor.
Lint & optimize
Run the linter for tag errors, beautify for readability, minify for deliverability, simulate dark mode.
Bulletproof for Outlook
Wrap CTAs and hero images in VML so every Outlook version renders exactly what you designed.
Send & ship
Fire a real test to your inbox, copy the final HTML, and paste it into your ESP. Done.
A code-first toolkit, not another drag-and-drop builder.
- Validate against 40+ client-specific rendering bugs
- Beautify or minify to slide under Gmail's 102KB cap
- Generate Outlook VML buttons and backgrounds in one click
- Auto-flag dark-mode contrast failures (WCAG AA)
Edit coded templates without ever opening a code editor.
- Click any block to update text, images, and links
- Pixel-perfect templates that survive Gmail clipping
- Hand off to developers without losing brand integrity
- Auto-save to your browser — pick up where you left off
What is an HTML email toolkit, and why do you need one?
An HTML email toolkit is a collection of utilities that helps developers and marketers build, validate, and optimize email campaigns for inbox rendering. Unlike web browsers, email clients (Gmail, Outlook, Apple Mail, Yahoo) parse HTML in wildly inconsistent ways — Outlook uses Microsoft Word as its rendering engine, Gmail strips style tags, and most clients ignore modern CSS entirely.
A good toolkit solves the three core problems of email development: validation (catching errors before they break a send), compatibility (generating VML fallbacks for Outlook), and deliverability (minifying to stay under Gmail's 102KB clipping threshold). EMLinter wraps all three into one free, browser-based workflow.
We built EMLinter because the existing market is split between expensive preview platforms (Litmus, Email on Acid) and drag-and-drop builders (BEE, Stripo) that produce bloated code. If you write HTML email by hand — or maintain templates someone else wrote — you need a fast, focused, code-first toolkit. That's what we shipped.
HTML email toolkit FAQs
Answers to the questions developers and marketers ask before they ship a campaign.
EMLinter is a free, browser-based HTML email toolkit built for email developers, marketers, and designers. It bundles a linter, beautifier, minifier, dark-mode tester, visual editor, and bulletproof Outlook generators into one workflow — so you can validate, debug, and ship pixel-perfect email campaigns without juggling six different tools.
Yes — every tool on EMLinter is 100% free with no signup required. Paste your HTML, click a button, copy the result. We don't gate features behind a login, and we don't store your code or personal data.
All processing happens locally in your browser. Your HTML never touches our servers — the linter, minifier, beautifier, dark-mode tester, and Outlook generators all run client-side. Nothing is uploaded, logged, or stored.
The toolkit targets every major client and rendering engine: Gmail (web, iOS, Android), Apple Mail, Outlook 2007–2024 (Word + WebView), Outlook.com, Yahoo Mail, Samsung Mail, Thunderbird, ProtonMail, and HEY. Our Outlook tools specifically generate VML fallbacks for the trickiest of the bunch.
Litmus and Email on Acid are paid rendering-preview platforms. Stripo and BEE are drag-and-drop builders. EMLinter sits between them — a free, code-first toolkit for people who already write or maintain HTML email and need fast, focused utilities (lint, minify, dark-mode preview, VML generators) without subscriptions or onboarding.
Yes. Every template in our library is plain, responsive HTML compatible with major ESPs — Mailchimp, Klaviyo, HubSpot, Constant Contact, Salesforce Marketing Cloud, Campaign Monitor, ActiveCampaign, and more. Edit the copy and images in our Visual Editor, copy the HTML, paste it into your ESP's code editor.
Ready to ship better emails?
Open the toolkit, paste your HTML, and see why thousands of email developers swapped their paid tools for EMLinter.