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Litmus alternatives

Litmus sends back pictures of your email, for a price. Hyper Elements builds it right, checks it as it renders, and previews it in Outlook, Gmail, Apple Mail and more, free and in milliseconds, with results your agent can read.

Try the free previews →Get started
  1. 1Hyper ElementsThe Litmus alternative built for coding agents
  2. 2ParcelBest for hand-coding emails, with real inbox screenshots
  3. 3MailosaurBest for real-device screenshots in automated tests

Litmus and its alternatives, side by side

FeatureHyper ElementsLitmusParcelMailosaur
What it isEmail engine, free previewsBuilder and testingEmail code editorQA testing
Results your agent can readYesFindings as JSONPartlyImages, API by requestNoImagesPartlyImages, API
Free previews on every changeYesUnlimitedNoContact salesNoPaid per previewNoPaid plan
Previews of real email clientsYesModeled, up to 99% matchYesScreenshotsYesScreenshotsYesScreenshots
Your email stays on your machineYesNoNoNo
In your tests and CIYesnpm package, CLIPartlyAPI by requestNoNot documentedYesAPI, SMTP
Build emailsYesReact componentsYesBuilderYesCode editorNo
Problems caught as you buildYesEach render, with the fixPartlyPre-send checklistYesProblem checkerPartlyCompatibility tests
Accessibility checksYesLintYesYesYesWCAG
Dark mode previewsPartlyOutlook for Mac, Apple Mail, YahooYesYesYes

Why pay for screenshots?

A screenshot service takes your email, renders it on its servers and sends back pictures. Hyper Elements draws each client on your machine and tells you, and your agent, what changed.

Screenshot services

  • Rendered on their servers, a test at a time
  • Paid per preview or per seat
  • Your email uploaded to them
  • A picture for someone to look at
  • Checked once, before you send

Hyper Elements

  • Milliseconds per preview, on your machine
  • Free and unlimited
  • Nothing leaves your machine
  • What each client changed, as data your agent fixes
  • Checked on every change, in CI

Its previews match the real clients up to 99%.

Try the free previews →

Your email in Outlook, Gmail and Apple Mail, previewed free

Drawn by Hyper Elements on your machine, from the email's HTML, on every change. No test send, no account, nothing uploaded.

The launch email as the emulator draws it in Classic Outlook
Classic Outlook97%
The launch email as the emulator draws it in Gmail
Gmail99%
The launch email as the emulator draws it in Apple Mail
Apple Mail98%
The launch email as the emulator draws it in Gmail app
Gmail app98%

The percentage is how closely each preview matches the real client. Outlook.com, Outlook for Mac, Yahoo Mail and AOL Mail are previewed too, and more clients are on the way.

Paste your email and preview it free →

The Litmus alternative built for coding agents

An agent can't look at a screenshot and know what to fix. With Hyper Elements it writes the email, checks it and reads what each client changed, in one loop.

What your agent reads
  • infoemail/outlook-degradedborderRadius on this Column in classic Outlook: square corners
  • infoemail/degradedhover on this Button in some email clients: no change (where it shows, keyboard focus gets it too)
  • infoemail/outlook-degradedletterSpacing on this Text in classic Outlook: normal spacing: Word keeps letter spacing but doesn't draw it

What a screenshot gives it: a PNG.

  • An agent skillnpx skills add hyper-elements/hyper-elementsTeaches your agent the components, the checks and how to fix what they find
  • A CLI made for loopsnpx hyper-elements check --jsonJSON lines and exit codes: it fixes each error until the run passes
  • WebMCP in the browsercheck_html_emailBrowser agents check any HTML email on the email testing page
  • 2.6× fasterAn agent reached a passing email 2.6× faster than with React Email, in our benchmark
Try the free previews →Set up your agent
1

Hyper Elements

The Litmus alternative built for coding agents

Build emails as React components, check each one as it renders, and preview it in Outlook, Gmail, Apple Mail and more in milliseconds, free, on your machine, with findings your agent reads and fixes.

Pick it if

  • A coding agent writes or edits your emails, and needs results it can read, not pictures
  • You want a preview on every change, in milliseconds, not a paid screenshot before each send
  • You want problems caught as each email renders, in tests and CI, with what to write instead
  • Your emails can't leave your machine: customer data, unreleased products, regulated content

Keep in mind

  • Modeled previews: for a pixel check on a rare client, keep a real inbox
  • No spam tests or analytics
Get started →Try the free previews
2

Parcel

Best for hand-coding emails, with real inbox screenshots

An email code editor with live preview, components, an HTML problem checker and an accessibility checker, plus screenshots from real inboxes and devices.

Pick it if

  • You hand-code email HTML and want an editor built for it
  • You want screenshots from real inboxes, in light and dark

Keep in mind

  • Every screenshot is paid, on top of a paid plan
  • No documented API, so no agent or CI loop
parcel.io →
3

Mailosaur

Best for real-device screenshots in automated tests

Email testing for QA teams: capture test emails over SMTP or an API, check them in CI, and screenshot them on real devices.

Pick it if

  • Your QA team tests emails end to end in CI
  • You want screenshots made on real devices, in light and dark

Keep in mind

  • No tools for building emails
  • Screenshots are made on its servers, on a paid plan
mailosaur.com →

Questions about Litmus alternatives

What is the best Litmus alternative?

For teams that build emails in code, and for coding agents, Hyper Elements: it builds each email, checks it as it renders, and previews it in Outlook, Gmail, Apple Mail and more, free and in milliseconds, with results an agent can read. If you hand-code email HTML and want screenshots from real inboxes, Parcel. If your QA team wants screenshots from real devices in its tests, Mailosaur.

Which Litmus alternative works best with AI coding agents?

Hyper Elements. Its agent skill teaches an agent the components and the checks, its CLI returns JSON and exit codes an agent acts on, and its previews report what each email client changed as data, where a screenshot is a picture an agent has to interpret. Browser agents can call its WebMCP tool, check_html_email, on the email testing page. In our benchmark, an agent reached a passing email 2.6× faster with Hyper Elements than with React Email.

Is there a free Litmus alternative?

Hyper Elements is free, with no account and no limit: the engine, its checks, and previews of classic Outlook, Outlook.com, Gmail, Apple Mail, Yahoo Mail and more on your machine. Parcel's free plan has its code editor and checks, but its inbox screenshots are a paid add-on. Mailosaur has a free trial.

How accurate are Hyper Elements' previews?

Each preview is modeled on the real client, not a screenshot of it. How closely it matches the real client: 97% for classic Outlook, 99% for Outlook.com, Gmail, Yahoo Mail and AOL Mail, and 97 to 98% for Outlook for Mac, the Gmail app and Apple Mail. Use them on every change, and real-device screenshots or a real inbox for a final check across many clients.

Can I preview emails I didn't build with Hyper Elements?

Yes. The previews take any complete HTML email: from MJML, React Email, an email builder's export or written by hand. Paste it into the email testing playground, or pass it to renderInEmailClients() from @hyper-elements/email-clients. React isn't needed.

Can I check emails in CI?

Yes. npx hyper-elements check fails the run on a template's errors, and npx hyper-elements preview email.html --findings writes a preview per client and reports what each one changed, so a test, a CI job or a coding agent can check every change.

Is my email uploaded anywhere?

Not with Hyper Elements. The engine, the previews and the CLI run on your machine, and the email testing playground runs in your browser. Only the images and fonts your email links to load from their own hosts.

When should I still use Litmus?

When you need screenshots of 100+ clients and devices, spam filter tests, team proofing or open analytics. Litmus doesn't publish prices: its pricing page asks you to contact sales, and Litmus is now part of Validity Engage.

Stop paying for screenshots

Build with Hyper Elements, check every render, and preview Outlook, Gmail and Apple Mail free, on every change.

Get started →Try the free previews

Also see: React Email alternatives · MJML alternatives · Hyper Elements vs React Email