HTML Email Compatibility Check
Checks an email’s HTML against what each mail client actually supports, points at the element that breaks, and shows what survives Gmail, Outlook and the rest side by side.
Paste the HTML of a message you are about to send and this says, per client, what will not survive it — and points at the element that did it. The support data is caniemail’s: tests run on real devices, each carrying the date it was last run. This site owns no rendering farm and never claims a preview is a screenshot.
Plain-text alternative (optional)
How to use it
Paste the HTML
The whole message, as it will be sent. If you also send a text/plain part, paste that too — otherwise you will be told, correctly, that you have none.
Read the findings in severity order
“Breaks” means it goes out wrong in a client people use; “cosmetic” means one client differs slightly. Each finding names the clients it applies to and the caniemail feature it rests on.
Jump to the element and take the rewrite
Clicking a finding highlights the exact run in your source. Where a rewrite can be generated it is built from that element’s own content — the flex row becomes the table holding your columns — and “apply” splices it in, leaving the rest of your file untouched.
Check the two panes
Left is what you wrote; right is what the selected client leaves. Turn images off — that is what most readers see first — and try the dark and phone toggles.
Common questions
Is the preview a screenshot of Gmail?
No, and nothing here will ever say it is. It is your HTML with that client’s documented stripping rules applied, drawn by the browser you are using. For Outlook on Windows the difference matters most: it renders through Microsoft Word, so the pane can tell you what Word would still have and not how Word would lay it out.
Why does it warn about size before 102 KB?
Because Gmail measures the assembled message, not your file. Transfer encoding, headers and a sending platform’s link rewriting all add to it, so a draft at 100 KB here goes out over the limit and gets cut, with the footer and the unsubscribe link behind “전체 메시지 보기”.
What about Naver, Daum and Kakao?
They are listed and they carry no verdicts, because no public test matrix covers them and this site has not measured them. Choosing one applies only the universal rules — scripts and forms removed — and the panel says the result is unverified. A confident row about Naver would be worse than an empty one.
Does my draft leave the browser?
No. The parsing, the rules and the preview all run in the tab, and the draft is kept only in this browser’s local storage so a reload does not lose it. Clearing the box removes it.
Feed it from
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What Gmail, Outlook, Apple Mail, Yahoo, Samsung Mail and Thunderbird support in HTML email, from caniemail’s device tests, with the date each was last tested.
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Email Client Support Table
What Gmail, Outlook, Apple Mail, Yahoo, Samsung Mail and Thunderbird support in HTML email, from caniemail’s device tests, with the date each was last tested.
Sent vs Delivered Comparison
Send a draft to a disposable address from your own account and see what the sending path rewrote — links wrapped in redirects, dropped style blocks, added beacons, the encoding used.
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Builds an email from blocks as table-based, inline-styled HTML with a VML-backed button, and writes the plain-text alternative from the same blocks.
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