border-collapse
CSS property · 19 supported, 0 partial, 0 unsupported across 21 clients
border-collapse controls whether adjacent table-cell borders share a single line or render as separate boxes. In email, it is essential to set border-collapse: collapse on every layout table to prevent unwanted gaps between cells in Outlook and Yahoo.
Client Support
| Client | Category | Engine | Support |
|---|---|---|---|
| Gmail | webmail | Gmail Web | Supported |
| Gmail Android | mobile | Gmail Mobile | Supported |
| Gmail iOS | mobile | Gmail Mobile | Supported |
| Outlook 365 | webmail | Outlook Web | Supported |
| Outlook (New) | desktop | Outlook Web | Supported |
| Outlook Classic | desktop | Microsoft Word | Supported |
| Outlook iOS | mobile | Outlook Mobile | Supported |
| Outlook Android | mobile | Outlook Mobile | Supported |
| Outlook for Mac | desktop | WebKit | Supported |
| Apple Mail | desktop | WebKit | Supported |
| Apple Mail iOS | mobile | WebKit | Supported |
| Yahoo Mail | webmail | Yahoo | Supported |
| Yahoo Mail Android | mobile | Yahoo | Supported |
| Yahoo Mail iOS | mobile | Yahoo | Supported |
| Samsung Mail | mobile | Samsung | Supported |
| Thunderbird | desktop | Gecko | Supported |
| HEY Mail | webmail | WebKit | Unknown |
| Proton Mail | webmail | Proton | Supported |
| AOL Mail | webmail | AOL | Supported |
| Fastmail | webmail | Fastmail | Unknown |
| Superhuman | desktop | Blink | Supported |
Client-by-client behaviour for border-collapse
Fully supports border-collapse (19): Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook (New), Outlook Classic, Outlook iOS, Outlook Android, Outlook for Mac, Apple Mail, Apple Mail iOS, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, Samsung Mail, Thunderbird, Proton Mail, AOL Mail, Superhuman.
Behaviour unverified in: HEY Mail, Fastmail.
When to use border-collapse in email
- Collapsing borders on layout tables to eliminate Outlook's default cellspacing.
- Building a clean grid of pricing tiers where adjacent cells share borders without doubling up.
- Separating cells visually with cellspacing instead of collapsed borders for card-style layouts.
Rendering behaviour and edge cases
- Without border-collapse: collapse, Outlook on Windows can render visible gaps between cells even when cellspacing="0" is set.
- Outlook 2007–2019 sometimes ignores border-collapse on nested tables , apply it explicitly to every <table>.
- border-collapse: separate enables border-spacing, but border-spacing itself is poorly supported in Outlook.
Recommended fallback strategy
Always set border-collapse: collapse via inline style on every layout <table>. Combine with cellspacing="0" cellpadding="0" border="0" attributes for full Outlook coverage.
Related Features
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Try Emailens FreeSupport data last updated Apr 27, 2026 · synced from caniemail.com via @emailens/engine.