border-collapse
CSS property · 19 supported, 0 partial, 0 unsupported across 21 clients
border-collapse is supported in every email client where behavior is verified, 19 of 21 as of Sep 2, 2026; HEY Mail, Fastmail remain untested.
- 5/7 webmail, 6/6 desktop, 8/8 mobile clients support border-collapse fully.
- Across all clients, only 6 of 298 tracked HTML/CSS features render identically everywhere.
Source: caniemail.com (MIT), via the Emailens engine. Last tested upstream Dec 20, 2023, synced by Emailens Sep 2, 2026.
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
Check your own HTML for border-collapse
Paste your own, or run the sample below. Analyzed in this page, with no signup and nothing stored.
Test your border-collapse layout across 21 email clients
Preview rendering, catch CSS issues, and see how border-collapse displays across Outlook, Gmail, and Apple Mail. Free, no account needed.
Instant live preview · No signup required · 21 email engines
Last tested upstream: · Last synced by Emailens:
caniemail.com (MIT) records Dec 20, 2023 as the last time border-collapse was tested in a real client, 2 years before this sync. Syncing copies that result forward, it does not re-test it. Carried in @emailens/engine data v0.12.2.