CSS property · data last changed 17 Oct 2026
css-comments in email clients
Works in 14 of 21. Partial in Gmail Android, Yahoo Mail Android, Yahoo Mail iOS and 1 more. Untested in HEY Mail, Fastmail and Superhuman.
caniemail (MIT) via @emailens/engine 0.16.1
What to do instead in Gmail Android
- Partial.
<style>tag not supported with non-google account. Comment insidestyle:attribute works.
No signup · Five clients free, Outlook Classic included · All 21 with an account
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css-comments is not among the 24 features we have screenshotted on real installs. The ones we have →
All 21 clients, problems first
| Client | Support |
|---|---|
| Gmail Android | Partial See caveat 1 |
| Yahoo Mail Android | Partial See caveat 2 |
| Yahoo Mail iOS | Partial See caveat 2 |
| AOL Mail | Partial See caveat 2 |
| HEY Mail | Untested |
| Fastmail | Untested |
| Superhuman | Untested |
Works in 14: Gmail, Gmail iOS, Outlook 365 and 11 more. Show all
| Client | Support |
|---|---|
| Gmail | Works |
| Gmail iOS | Works |
| Outlook 365 | Works |
| Outlook (New) | Works |
| Outlook Classic | Works |
| Outlook iOS | Works |
| Outlook Android | Works |
| Outlook for Mac | Works |
| Apple Mail | Works |
| Apple Mail iOS | Works |
| Yahoo Mail | Works |
| Samsung Mail | Works |
| Thunderbird | Works |
| Proton Mail | Works |
Caveats (2)
- 1. Gmail Android: Partial.
<style>tag not supported with non-google account. Comment insidestyle:attribute works. - 2. Yahoo Mail Android, Yahoo Mail iOS, AOL Mail: Buggy. The first <head> in the HTML is removed, so comment needs to be in the
<style>tag of a second<head>element.
Caveats as recorded by caniemail (MIT), one entry per wording.
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