Selector or pseudo-class · data last changed 10 Nov 2026
:chaining in email clients
Works in 14 of 21. Not supported in Outlook 365, Outlook (New), Outlook Classic and 1 more. Partial in Gmail Android and Gmail iOS. Untested in Superhuman.
Your reader in Outlook Classic sees the email without :chaining, even if it looks right where you tested it.
caniemail (MIT) via @emailens/engine 0.18.22
What to do instead in Outlook Classic
Use chained selectors in <style> blocks for progressive enhancement only. For Outlook compatibility, inline the equivalent styles on the matching elements directly.
- Buggy. Styles will be applied to the first selector of the chain.
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:chaining is not among the 24 features we have screenshotted on real installs. The ones we have →
All 21 clients, problems first
| Client | Support |
|---|---|
| Outlook 365 | Not supported See caveat 2 |
| Outlook (New) | Not supported See caveat 2 |
| Outlook Classic | Not supported See caveat 3 |
| Proton Mail | Not supported |
| Gmail Android | Partial See caveat 1 |
| Gmail iOS | Partial See caveat 1 |
| Superhuman | Untested |
Works in 14: Gmail, Outlook iOS, Outlook Android and 11 more. Show all
| Client | Support |
|---|---|
| Gmail | Works |
| Outlook iOS | Works |
| Outlook Android | Works |
| Outlook for Mac | Works |
| Apple Mail | Works |
| Apple Mail iOS | Works |
| Yahoo Mail | Works |
| Yahoo Mail Android | Works |
| Yahoo Mail iOS | Works |
| Samsung Mail | Works |
| Thunderbird | Works |
| HEY Mail | Works |
| AOL Mail | Works |
| Fastmail | Works |
Caveats (3)
- 1. Gmail Android, Gmail iOS: Partial. Not supported with non Google accounts.
- 2. Outlook 365, Outlook (New): Buggy. Only the first selector of the chain is prefixed in the styles, but all classes are prefixed in the HTML.
- 3. Outlook Classic: Buggy. Styles will be applied to the first selector of the chain.
Caveats as recorded by caniemail (MIT), one entry per wording.
How :chaining behaves
Selector chaining (combining classes or tags without a separator, e.g., .button.primary) increases specificity by requiring multiple conditions on the same element. In email, chained selectors live in <style> blocks and only apply where <style> is preserved.
- Outlook strips <style>, so chained selectors do not apply there.
- Gmail's class-rewriting can break selectors that depend on multiple class names matching.
- Specificity from chaining is additive, a chained selector outranks a single class.
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