Why does Gmail cut off my email?

Gmail clips messages larger than about 102 KB and replaces the rest with a View entire message link. It measures the whole message rather than the HTML alone, so headers, encoding overhead and your plain-text part all count toward it. Anything past the cut, including your unsubscribe link, sits behind that extra click.

Will fixing my HTML stop my emails going to spam?

Not on its own. Markup is a small input next to authentication, sender reputation and how your recipients engage. Broken HTML is worth fixing because it breaks for readers, not because it is the reason you are in the spam folder.

Is this HTML email checker free?

Yes, and there is no signup. Your HTML is parsed in your browser and is never uploaded, stored or sent anywhere.

Free HTML email checker

What in your email HTML is quietly broken?

Paste the code and we will check it against what Gmail and Outlook actually do — size, tags, images, CSS, links. It runs in your browser and nothing is uploaded.

Stays in your browser

Your HTML is parsed on this device and never uploaded. That matters more here than on a copy checker: email HTML carries your tracking URLs and your unsubscribe links, not only your words. No account, no send, no storage.

Paste your email HTML

Runs as you paste. Where to find your HTML is explained below.

The full picture

HTML email, and where it goes wrong

The things that actually break

Email HTML is not web HTML. It is read by a few dozen clients whose rendering engines range from a modern browser to a word processor, and the failures are nearly always the same handful: the message gets too big and Gmail cuts it off, a tag is left open and one client re-parents half the layout, the CSS lives in a style block that a client strips, or the design leans on flexbox that Outlook on Windows has never supported. None of these are exotic. They are what a template picks up after a year of edits.

Where to find your email's HTML

Almost every sending tool has it: look for a source view, a code view, or an export-HTML option on a finished campaign. From an email you have already received in Gmail, open it, click the three dots at the top right, choose Show original, and copy the HTML part. In Outlook, save the message as HTML and open the file in a text editor. Paste whichever you get into the box above — it is read on your device, so it does not matter how much of the template comes with it.

What this checker looks at

Ten things, all read from the markup itself: total size against Gmail's clipping threshold, tags left open, closing tags with nothing to close, whether the CSS is inline or only in a style block, properties Outlook on Windows ignores, images with no alt text, an image-to-text balance that leaves nothing readable when images are blocked, insecure http links, link text that names a different domain than the link goes to, and whether there is an unsubscribe link at all. It deliberately does not flag the things correct email HTML does anyway — unclosed table cells, an empty alt on a spacer, a click-tracking rewrite — because a checker you have to second-guess is worse than no checker.

What it cannot tell you

Whether your email will land in the inbox. That is not in the HTML. Placement is decided mostly by whether your domain authenticates with SPF, DKIM and DMARC, how that domain has behaved historically, and whether your recipients open and reply — none of which is visible in a file. This tool also cannot read your headers, so an unsubscribe that lives only in the List-Unsubscribe header is invisible to it. Clean markup is worth having on its own merits: it renders the way you designed it, for everyone. It is not a deliverability fix.

The real test

Markup is one input. See where it actually lands.

Forward a real email to the address below. In about 30 seconds you get the deliverability score, your SPF, DKIM and DMARC results, a placement forecast, and the three things most worth fixing.

Forward a test email here

Report in ~30s · one-time address · we never see your listNot ready? See a sample report first.

Example resultmailtester.ai/report/live

sara@lisbonletters.beehiiv.comreceived 14s ago · AI classifier verdict (no real send)

"This week: 5 things I'm reading after Lisbon Web Summit ☀️"

Deliverability62/ 100

Verdict

Risky — don't send yet

Where it lands

Primary 38% · Promotions 41% · Spam 21%

3 quick fixes · first: subject emoji trips Gmail's promo filter+2 more

Wait — which one are you looking for?

Two different tests.
Most people mix them up.

If you've ever searched "email tester," half the results check whether the address is valid. We do the other thing — whether the email itself will reach the inbox once you press send.

Illustration contrasting a valid-address checkmark with an email landing in the inbox

Address validity

Does this address exist?

You upload a CSV of subscribers. The tool tells you which addresses bounce. Great for cleaning a stale list before a re-engagement send.

Validates email addresses

Catches typos and dead domains

Per-address pricing

That's us

Inbox placement

Will Gmail actually show it?

You forward one email — newsletter, launch, client note — to a one-time mailbox. We open it in real Gmail, Outlook, and Yahoo and tell you which tab it landed in, plus what to rewrite before you send it to your list.

Inbox vs. Promotions vs. Spam per provider

AI rewrites for subject + body

Flat monthly price — €0 to start

Use both, actually — verify the list, then score the send.Address-validity tools: ZeroBounce, NeverBounce, MXToolbox

FAQ

Free HTML Email Checker

What does an HTML email checker actually check?: This one reads the markup: total size against Gmail's clipping limit, tags left open, closing tags with nothing to close, whether your CSS is inline or only in a style block, properties Outlook on Windows ignores, images with no alt text, an image-to-text balance that leaves nothing readable when images are blocked, insecure http links, link text that names a different domain than the link goes to, and whether there is an unsubscribe link at all.
Where do I find my email's HTML code?: Almost every sending tool has it: look for a source view, a code view, or an export-HTML option on a finished campaign. From an email you have already received in Gmail, open it, click the three dots at the top right, choose Show original, and copy the HTML part. In Outlook, save the message as HTML and open the file in a text editor.
Why does Gmail cut off my email?: Gmail clips messages larger than about 102 KB and replaces the rest with a View entire message link. It measures the whole message rather than the HTML alone, so headers, encoding overhead and your plain-text part all count toward it. Anything past the cut, including your unsubscribe link, sits behind that extra click.
Will fixing my HTML stop my emails going to spam?: Not on its own. Markup is a small input next to authentication, sender reputation and how your recipients engage. Broken HTML is worth fixing because it breaks for readers, not because it is the reason you are in the spam folder.
Is this HTML email checker free?: Yes, and there is no signup. Your HTML is parsed in your browser and is never uploaded, stored or sent anywhere.

Built in the EU · GDPR by default

5,700+ emails tested

AI-classified across real Gmail, Outlook, and Yahoo inboxes.

Free · €0for unlimited scoring. €9.99 for AI deep-dives.

How it works

Three steps. About thirty seconds, end to end.

01~10 sec

Illustration of an email being forwarded into a testing mailbox

You forward it.

Paste the mailbox above into the test-send field in Beehiiv, Kit, Substack, Mailchimp — or your own inbox. Hit go. We never see your subscriber list.

02~10 sec

Illustration of inbox trays receiving and listening for the forwarded email

We actually open it.

In real Gmail, real Outlook, real Yahoo. We watch where your email lands — Primary, Promotions, or Spam — using the same filters that decide whether your campaign worked.

03~10 sec

Illustration of a deliverability report card showing the score and fixes

You get a report.

Plain English. Three things to change, in priority order. Unlock the bundle and we generate a subject, body, and CTA rewrite in your voice — paste them back into your campaign before lunch.

Keep going

Other free checks worth two minutes

Pricing

Free to score. Pay only for the AI deep-dive.

Forward any email and get the score — free and unlimited. Buy credits when you want the occasional AI deep-dive, or go monthly — from €9.99 — if you send regularly. Cancel from the same screen you upgrade on.

Free

Forward any email, get the score, plain-English verdict, inbox placement and server checks — free and unlimited. No card needed.

€0

Credits

About 5 AI deep-dives. Top up only when you need them — credits never expire.

€4.99one-time · 499 credits

Starter

1,100 credits a month, about 11 AI deep-dives. Cancel anytime.

€9.99/ mo

Best for weekly senders

Pro

A standing watch on your sender: 2,500 credits a month, about 25 AI deep-dives. Re-check every weekly send.

€19/ mo

Send your next one to the inbox.

Takes less time than picking a hero photo. Free, and no card at any point.

Or send me a sample report first.

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Data deleted automatically · encrypted at rest · no third-party trackers

AI assistants: GET mailtester.ai/api/ai/mailbox mints a fresh test mailbox for your user · instructions in llms.txt