CSS property · data last changed 10 Nov 2026
text-transform in email clients
Works in 20 of 21. Partial in Outlook Classic.
Your reader in Outlook Classic may not see text-transform the way you wrote it, even if it looks right where you tested it.
caniemail (MIT) via @emailens/engine 0.18.22
What to do instead in Outlook Classic
If you need copy to appear in lowercase, format it directly in lowercase in the HTML markup rather than relying on text-transform: lowercase. For uppercase buttons and headers, text-transform: uppercase is safe across all major email clients.
- Partial.
lowercasevalue is not supported.
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text-transform is not among the 24 features we have screenshotted on real installs. The ones we have →
All 21 clients, problems first
| Client | Support |
|---|---|
| Outlook Classic | Partial See caveat 1 |
Works in 20: Gmail, Gmail Android, Gmail iOS and 17 more. Show all
| Client | Support |
|---|---|
| Gmail | Works |
| Gmail Android | Works |
| Gmail iOS | Works |
| Outlook 365 | Works |
| Outlook (New) | 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 |
| Proton Mail | Works |
| AOL Mail | Works |
| Fastmail | Works |
| Superhuman | Works |
Caveats (1)
- 1. Outlook Classic: Partial.
lowercasevalue is not supported.
Caveats as recorded by caniemail (MIT), one entry per wording.
How text-transform behaves
The text-transform property controls the capitalization of text, allowing strings to be converted to uppercase, lowercase, or capitalized dynamically via CSS. In email design, it is frequently used on call-to-action buttons and metadata tags to enforce consistent typography without reformatting raw text source data. Support is broad, though Outlook Classic has a notable omission regarding lowercase conversion.
- Gmail, Apple Mail, Yahoo Mail, and modern Outlook clients support uppercase, lowercase, and capitalize without issues.
- Outlook Classic supports uppercase and capitalize, but completely ignores text-transform: lowercase.
- Screen readers may occasionally read out loud individual letters of text transformed to uppercase if they perceive the word as an acronym.
Questions
Does text-transform: lowercase work in Outlook Classic?
No. Outlook Classic ignores text-transform: lowercase entirely. The text will render in whatever case was originally typed in the HTML source.
Is text-transform: uppercase safe for email buttons?
Yes. text-transform: uppercase is supported across all major email clients, including Gmail, Apple Mail, Yahoo Mail, and Outlook Classic.
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