← CSS Support IndexDoes CSS
Does CSS initial unit Work in HTML Email?
Support for initial keyword value.
Quick Answer
Does initial unit work in HTML email?
The CSS initial unit property is supported in Outlook (Mac / Web), Apple Mail, Samsung Email, Thunderbird, and others. It is NOT supported in Outlook (Windows), Yahoo! Mail. Always include a safe fallback for unsupported clients.
Which Email Clients Support CSS initial unit?
CSS support for initial unit across email clients
| Email Client | Desktop | Mobile / Web | Notes |
|---|---|---|---|
| Gmail | ~ Partial | ~ Partial | — |
| Outlook (Windows) | ✗ No | ? | — |
| Outlook (Mac / Web) | ✓ Yes | ✓ Yes | — |
| Apple Mail | ✓ Yes | ✓ Yes | — |
| Yahoo! Mail | ✗ No | ✗ No | — |
| Samsung Email | ? | ✓ Yes | — |
| Thunderbird | ✓ Yes | ? | — |
| ProtonMail | ✓ Yes | ✓ Yes | — |
| Fastmail | ✓ Yes | ? | — |
Notes
- #1 Partial. Webmail rendering doesn't work in IE.
- #2 Partial. Not supported with non Google accounts.
Frequently Asked Questions
Test Your Email Now
Paste your HTML and see how it renders in clients that don't support initial unit.