How many email clients support opacity?

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

Does opacity work in Outlook (New)?

opacity works in Outlook (New). Closest to Outlook for Mac: Outlook (New), which agrees on 279 of the 299 features both are tested on.

opacity in Outlook for Mac

Works opacity works in Outlook for Mac.

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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Your next question

Every feature in Outlook for Mac · opacity in every client

Questions

How many email clients support opacity?: It works in 19 of 21, not supported in Outlook Classic and AOL Mail.
Does opacity work in Outlook (New)?: opacity works in Outlook (New). Closest to Outlook for Mac: Outlook (New), which agrees on 279 of the 299 features both are tested on.

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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