CSS property · 11 real installs 14 Oct 2026 · data last changed 10 Nov 2026

visibility in email clients

Works in 13 of 21. Not supported in Gmail, Gmail Android, Gmail iOS and 5 more.

Your reader in Outlook Classic sees the email without visibility, even if it looks right where you tested it.

caniemail (MIT) via @emailens/engine 0.18.22

The fix for Outlook Classic

Use conditional comments or remove hidden content

The engine still flags this in the fix: Outlook Classic does not support "max-height".

after

5 lines

<!-- For screen readers, use font-size: 0 trick -->
<div style="font-size: 0; max-height: 0; overflow: hidden;
            mso-hide: all;" aria-hidden="true">
  Preheader text
</div>

Show the original

before

3 lines

<div style="visibility: hidden;">
  Hidden content for screen readers
</div>

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visibility on 11 real installs

One Emailens probe, screenshotted on each install on 14 October 2026, next to our live preview of the same client. Where visibility is supported you should see: a, gap, b (no hidden word).

The Emailens probe for visibility on a real Outlook 2019 (Windows) — Outlook Classic

The Emailens probe for visibility on a real Outlook 2016 (Windows) — Outlook Classic

The Emailens probe for visibility on a real Yahoo Mail — Yahoo Mail

The same probe in the Emailens live preview of Yahoo Mail — Yahoo Mail

The Emailens probe for visibility on a real Outlook.com — Outlook 365

The same probe in the Emailens live preview of Outlook 365 — Outlook 365

The Emailens probe for visibility on a real Apple Mail (macOS) — Apple Mail

The same probe in the Emailens live preview of Apple Mail — Apple Mail

The Emailens probe for visibility on a real Apple Mail (iPhone 13) — Apple Mail iOS

The same probe in the Emailens live preview of Apple Mail iOS — Apple Mail iOS

Also captured, not counted as evidence (4)

Outlook for Microsoft 365 · not mapped to an engine client yet Real screenshot
Outlook 2019 for Mac (legacy app) · not counted as Outlook for Mac Real screenshot
This is the legacy Outlook for Mac app. The new Outlook for Mac, which the table describes, drops gradients, grid sizing functions, var() and more.
Gmail (web) · not counted as Gmail Real screenshot
This Gmail install does not apply Gmail's sanitiser, so it shows more than real Gmail does.
Windows Mail · not mapped to an engine client yet Real screenshot

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All 21 clients, problems first

Client	Support
Gmail	Not supported
Gmail Android	Not supported
Gmail iOS	Not supported
Outlook Classic	Not supported
Outlook Android	Not supported ^{See caveat 2}
Yahoo Mail	Not supported ^{See caveat 3}
Yahoo Mail Android	Not supported ^{See caveat 4}
AOL Mail	Not supported

Works in 13: Outlook 365, Outlook (New), Outlook iOS and 10 more. Show all

Client	Support
Outlook 365	Works
Outlook (New)	Works
Outlook iOS	Works ^{See caveat 1}
Outlook for Mac	Works ^{See caveat 1}
Apple Mail	Works ^{See caveat 1}
Apple Mail iOS	Works ^{See caveat 1}
Yahoo Mail iOS	Works ^{See caveat 1}
Samsung Mail	Works
Thunderbird	Works
HEY Mail	Works
Proton Mail	Works ^{See caveat 1}
Fastmail	Works
Superhuman	Works

Caveats (4)

1. Outlook iOS, Outlook for Mac, Apple Mail, Apple Mail iOS, Yahoo Mail iOS, Proton Mail: Buggy. visibility:collapse applied to a <tr> only hides content and does not "remove" it from layout.
2. Outlook Android: Observed 2026-11-08 (Emailens probe sheets 20-22, the Outlook Android app, our own seed inbox): An element at visibility:hidden stayed visible. Use display:none (or remove the element) to hide it.
3. Yahoo Mail: Observed 2026-11-08 (Emailens probe sheets 20-22, Yahoo Mail web (Chrome), our own seed inbox): An element at visibility:hidden stayed visible. Use display:none (or remove the element) to hide it.
4. Yahoo Mail Android: Observed 2026-11-08 (Emailens probe sheets 20-22, the Yahoo Mail Android app, our own seed inbox): An element at visibility:hidden stayed visible. Use display:none (or remove the element) to hide it.

Caveats as recorded by caniemail (MIT), one entry per wording.

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