How many email clients support opacity?

It works in 19 of 21, not supported in Outlook Classic and AOL Mail.

opacity in Superhuman

Works opacity works in Superhuman.

Works in 19 of 21 · not supported in 2

Which clients

Works: Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook (New), Outlook iOS, Outlook Android, Outlook for Mac, Apple Mail, Apple Mail iOS, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, Samsung Mail, Thunderbird, HEY Mail, Proton Mail, Fastmail, Superhuman
Not supported: Outlook Classic, AOL Mail

The fix for the clients that need it

Needed in 2 of 21: Outlook Classic and AOL Mail.

Replace opacity with solid color equivalents

instead

5 lines

.overlay {
  /* Use a semi-transparent color instead of opacity */
  background-color: #808080;
  /* Or for modern clients: rgba(0, 0, 0, 0.5) */
}

Show the original

before

4 lines

.overlay {
  background-color: #000;
  opacity: 0.5;
}

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Questions

How many email clients support opacity?: It works in 19 of 21, not supported in Outlook Classic and AOL Mail.

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caniemail (MIT) via @emailens/engine 0.18.22 · tested upstream 28 Feb 2019 · data last changed 10 Nov 2026 · Outlook (New) cells are the engine's mapping