HTML Elements

<dialog>

HTML element · 6 supported, 0 partial, 14 unsupported across 21 clients

As of Sep 2, 2026, <dialog> fails or degrades in 15 of 21 email clients, treat it as progressive enhancement, never structure.

0/7 webmail, 3/6 desktop, 3/8 mobile clients support <dialog> fully.
Unsupported in Gmail, Gmail iOS, Outlook 365, Outlook (New) and 10 more.
Outlook Classic (Word engine, supported to at least 2029) does not fully support <dialog>, and its replacement changes little here; see the deprecation diff.
Across all clients, only 6 of 298 tracked HTML/CSS features render identically everywhere.

Source: caniemail.com (MIT), via the Emailens engine. Last tested upstream Feb 28, 2019, synced by Emailens Sep 2, 2026.

The <dialog> element represents a modal or non-modal dialog. It is unsupported in essentially every email client because email is not an interactive surface. Including <dialog> in email markup is harmless , the content inside renders as a regular block , but the open/close behavior never works.

Client Support

Client	Category	Engine	Support
Gmail	webmail	Gmail Web	Unsupported
Gmail Android	mobile	Gmail Mobile	Supported
Gmail iOS	mobile	Gmail Mobile	Unsupported
Outlook 365	webmail	Outlook Web	Unsupported
Outlook (New)	desktop	Outlook Web	Unsupported
Outlook Classic	desktop	Microsoft Word	Unsupported
Outlook iOS	mobile	Outlook Mobile	Unsupported
Outlook Android	mobile	Outlook Mobile	Unsupported
Outlook for Mac	desktop	WebKit	Supported
Apple Mail	desktop	WebKit	Supported
Apple Mail iOS	mobile	WebKit	Supported
Yahoo Mail	webmail	Yahoo	Unsupported
Yahoo Mail Android	mobile	Yahoo	Unsupported
Yahoo Mail iOS	mobile	Yahoo	Unsupported
Samsung Mail	mobile	Samsung	Supported
Thunderbird	desktop	Gecko	Supported
HEY Mail	webmail	WebKit	Unsupported
Proton Mail	webmail	Proton	Unsupported
AOL Mail	webmail	AOL	Unsupported
Fastmail	webmail	Fastmail	Unsupported
Superhuman	desktop	Blink	Unknown

Client-by-client behaviour for <dialog>

Fully supports <dialog> (6): Gmail Android, Outlook for Mac, Apple Mail, Apple Mail iOS, Samsung Mail, Thunderbird.

No support (14): Gmail, Gmail iOS, Outlook 365, Outlook (New), Outlook Classic, Outlook iOS, Outlook Android, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, HEY Mail, Proton Mail, AOL Mail, Fastmail. Plan fallbacks for these clients before relying on <dialog> in production sends.

Behaviour unverified in: Superhuman.

When to use <dialog> in email

Including <dialog> as a semantic wrapper for fallback content that renders as block-level text.
AMP for Email contexts where lightbox-style interactions are supported (rare and Gmail-only).
Future-proofing markup for clients that may eventually honor dialog semantics.

Rendering behaviour and edge cases

<dialog> renders as a block-level element with default styling, but no clients honor its open/show behavior.
Most clients ignore the open attribute entirely.
AMP for Email provides interactive lightboxes through dedicated AMP components, not native <dialog>.

Recommended fallback strategy

Avoid <dialog> in production email. If you need a 'modal' visual treatment, build a styled card with table cells and let it render inline in the email flow.