border-collapse
CSS property · 14 supported, 0 partial, 0 unsupported across 15 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 |
| Apple Mail | desktop | WebKit | Supported |
| Apple Mail iOS | mobile | WebKit | Supported |
| Yahoo Mail | webmail | Yahoo | Supported |
| Samsung Mail | mobile | Samsung | Supported |
| Thunderbird | desktop | Gecko | Supported |
| HEY Mail | webmail | WebKit | Unknown |
| Superhuman | desktop | Blink | Supported |
Client-by-client behaviour for border-collapse
Fully supports border-collapse (14): Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook (New), Outlook Classic, Outlook iOS, Outlook Android, Apple Mail, Apple Mail iOS, Yahoo Mail, Samsung Mail, Thunderbird, Superhuman.
Behaviour unverified in: HEY Mail.
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.