CSS Properties

gap

CSS property · 8 supported, 7 partial, 6 unsupported across 21 clients

8 of 21 email clients render gap fully (Sep 2, 2026 data); it breaks outright in Outlook (New), Outlook Classic, Yahoo Mail and 3 more.

2/7 webmail, 4/6 desktop, 2/8 mobile clients support gap fully.
Unsupported in Outlook (New), Outlook Classic, Yahoo Mail, Yahoo Mail Android and 2 more.
Partial in Gmail, Gmail Android, Gmail iOS, Outlook 365 and 3 more, behavior differs from browsers, test before relying on it.
Outlook Classic (Word engine, supported to at least 2029) does not fully support gap, and its replacement changes little here; see the deprecation diff.
Documented before/after fixes on this page cover 21 clients, including Gmail and Gmail Android.
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 28, 2022, synced by Emailens Sep 2, 2026.

Client Support

Client	Category	Engine	Support
Gmail	webmail	Gmail Web	Partial^{See caveat 1}
Gmail Android	mobile	Gmail Mobile	Partial^{See caveat 1}
Gmail iOS	mobile	Gmail Mobile	Partial^{See caveat 1}
Outlook 365	webmail	Outlook Web	Partial^{See caveat 1}
Outlook (New)	desktop	Outlook Web	Unsupported
Outlook Classic	desktop	Microsoft Word	Unsupported
Outlook iOS	mobile	Outlook Mobile	Partial^{See caveat 1}
Outlook Android	mobile	Outlook Mobile	Partial^{See caveat 1}
Outlook for Mac	desktop	WebKit	Supported
Apple Mail	desktop	WebKit	Supported
Apple Mail iOS	mobile	WebKit	Supported
Yahoo Mail	webmail	Yahoo	Unsupported
Yahoo Mail Android	mobile	Yahoo	Unsupported
Yahoo Mail iOS	mobile	Yahoo	Unsupported
Samsung Mail	mobile	Samsung	Supported
Thunderbird	desktop	Gecko	Supported
HEY Mail	webmail	WebKit	Supported
Proton Mail	webmail	Proton	Supported
AOL Mail	webmail	AOL	Unsupported
Fastmail	webmail	Fastmail	Partial^{See caveat 2}
Superhuman	desktop	Blink	Supported

Documented caveats (2)

1.Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook iOS, Outlook Android: Partial. Supports column-gap for flexbox.
2.Fastmail: Partial. Supports gap and column-gap for flexbox. Supports gap for multi-column layout (i.e. in conjunction with CSS column-count property)

Caveats recorded by caniemail.com (MIT) and carried verbatim, one entry per wording rather than per client.

Client-by-client behaviour for gap

Fully supports gap (8): Outlook for Mac, Apple Mail, Apple Mail iOS, Samsung Mail, Thunderbird, HEY Mail, Proton Mail, Superhuman.

Partial support (7): Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook iOS, Outlook Android, Fastmail. Expect rendering quirks unique to each engine. Partial support typically means a subset of values, an ignored shorthand, or sanitizer-specific rewrites.

No support (6): Outlook (New), Outlook Classic, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, AOL Mail. Plan fallbacks for these clients before relying on gap in production sends.

Fixes & Workarounds

Outlook (New)

Unsupported

Use padding/margin on child elements instead of gap.

Before (Broken)

before.html

5 lines

<div style="display: flex; gap: 16px;">
  <div>Item 1</div>
  <div>Item 2</div>
  <div>Item 3</div>
</div>

After (Fixed)

fixed.html

8 lines

<table role="presentation" cellpadding="0"
  cellspacing="0" border="0">
  <tr>
    <td style="padding-right: 16px;">Item 1</td>
    <td style="padding-right: 16px;">Item 2</td>
    <td>Item 3</td>
  </tr>
</table>

Use padding or margin on child elements instead of gap

Outlook Classic

Unsupported

Use cellpadding/cellspacing on tables, or padding on cells.

Before (Broken)

before.html

5 lines

<div style="display: flex; gap: 16px;">
  <div>Item 1</div>
  <div>Item 2</div>
  <div>Item 3</div>
</div>

After (Fixed)

fixed.html

8 lines

<table role="presentation" cellpadding="0"
  cellspacing="0" border="0">
  <tr>
    <td style="padding-right: 16px;">Item 1</td>
    <td style="padding-right: 16px;">Item 2</td>
    <td>Item 3</td>
  </tr>
</table>

Use padding or margin on child elements instead of gap

Yahoo Mail

Unsupported

Use padding/margin on child elements instead of gap.

Before (Broken)

before.html

5 lines

<div style="display: flex; gap: 16px;">
  <div>Item 1</div>
  <div>Item 2</div>
  <div>Item 3</div>
</div>

After (Fixed)

fixed.html

8 lines

<table role="presentation" cellpadding="0"
  cellspacing="0" border="0">
  <tr>
    <td style="padding-right: 16px;">Item 1</td>
    <td style="padding-right: 16px;">Item 2</td>
    <td>Item 3</td>
  </tr>
</table>

Use padding or margin on child elements instead of gap

Yahoo Mail Android

Unsupported

Use padding/margin on child elements instead of gap.

Before (Broken)

before.html

5 lines

<div style="display: flex; gap: 16px;">
  <div>Item 1</div>
  <div>Item 2</div>
  <div>Item 3</div>
</div>

After (Fixed)

fixed.html

8 lines

<table role="presentation" cellpadding="0"
  cellspacing="0" border="0">
  <tr>
    <td style="padding-right: 16px;">Item 1</td>
    <td style="padding-right: 16px;">Item 2</td>
    <td>Item 3</td>
  </tr>
</table>

Use padding or margin on child elements instead of gap

Yahoo Mail iOS

Unsupported

Use padding/margin on child elements instead of gap.

Before (Broken)

before.html

5 lines

<div style="display: flex; gap: 16px;">
  <div>Item 1</div>
  <div>Item 2</div>
  <div>Item 3</div>
</div>

After (Fixed)

fixed.html

8 lines

<table role="presentation" cellpadding="0"
  cellspacing="0" border="0">
  <tr>
    <td style="padding-right: 16px;">Item 1</td>
    <td style="padding-right: 16px;">Item 2</td>
    <td>Item 3</td>
  </tr>
</table>

Use padding or margin on child elements instead of gap

AOL Mail

Unsupported

Use padding/margin on child elements instead of gap.

Before (Broken)

before.html

5 lines

<div style="display: flex; gap: 16px;">
  <div>Item 1</div>
  <div>Item 2</div>
  <div>Item 3</div>
</div>

After (Fixed)

fixed.html

8 lines

<table role="presentation" cellpadding="0"
  cellspacing="0" border="0">
  <tr>
    <td style="padding-right: 16px;">Item 1</td>
    <td style="padding-right: 16px;">Item 2</td>
    <td>Item 3</td>
  </tr>
</table>

Use padding or margin on child elements instead of gap

Gmail

Partial

Use padding/margin on child elements instead of gap.

Before (Broken)

before.html

5 lines

<div style="display: flex; gap: 16px;">
  <div>Item 1</div>
  <div>Item 2</div>
  <div>Item 3</div>
</div>

After (Fixed)

fixed.html

8 lines

<table role="presentation" cellpadding="0"
  cellspacing="0" border="0">
  <tr>
    <td style="padding-right: 16px;">Item 1</td>
    <td style="padding-right: 16px;">Item 2</td>
    <td>Item 3</td>
  </tr>
</table>

Use padding or margin on child elements instead of gap

Gmail Android

Partial

Use padding/margin on child elements instead of gap.

Before (Broken)

before.html

5 lines

<div style="display: flex; gap: 16px;">
  <div>Item 1</div>
  <div>Item 2</div>
  <div>Item 3</div>
</div>

After (Fixed)

fixed.html

8 lines

<table role="presentation" cellpadding="0"
  cellspacing="0" border="0">
  <tr>
    <td style="padding-right: 16px;">Item 1</td>
    <td style="padding-right: 16px;">Item 2</td>
    <td>Item 3</td>
  </tr>
</table>

Use padding or margin on child elements instead of gap

Gmail iOS

Partial

Use padding/margin on child elements instead of gap.

Before (Broken)

before.html

5 lines

<div style="display: flex; gap: 16px;">
  <div>Item 1</div>
  <div>Item 2</div>
  <div>Item 3</div>
</div>

After (Fixed)

fixed.html

8 lines

<table role="presentation" cellpadding="0"
  cellspacing="0" border="0">
  <tr>
    <td style="padding-right: 16px;">Item 1</td>
    <td style="padding-right: 16px;">Item 2</td>
    <td>Item 3</td>
  </tr>
</table>

Use padding or margin on child elements instead of gap

Outlook 365

Partial

Use padding/margin on child elements instead of gap.

Before (Broken)

before.html

5 lines

<div style="display: flex; gap: 16px;">
  <div>Item 1</div>
  <div>Item 2</div>
  <div>Item 3</div>
</div>

After (Fixed)

fixed.html

8 lines

<table role="presentation" cellpadding="0"
  cellspacing="0" border="0">
  <tr>
    <td style="padding-right: 16px;">Item 1</td>
    <td style="padding-right: 16px;">Item 2</td>
    <td>Item 3</td>
  </tr>
</table>

Use padding or margin on child elements instead of gap

Outlook iOS

Partial

Use padding/margin on child elements instead of gap.

Before (Broken)

before.html

5 lines

<div style="display: flex; gap: 16px;">
  <div>Item 1</div>
  <div>Item 2</div>
  <div>Item 3</div>
</div>

After (Fixed)

fixed.html

8 lines

<table role="presentation" cellpadding="0"
  cellspacing="0" border="0">
  <tr>
    <td style="padding-right: 16px;">Item 1</td>
    <td style="padding-right: 16px;">Item 2</td>
    <td>Item 3</td>
  </tr>
</table>

Use padding or margin on child elements instead of gap

Outlook Android

Partial

Use padding/margin on child elements instead of gap.

Before (Broken)

before.html

5 lines

<div style="display: flex; gap: 16px;">
  <div>Item 1</div>
  <div>Item 2</div>
  <div>Item 3</div>
</div>

After (Fixed)

fixed.html

8 lines

<table role="presentation" cellpadding="0"
  cellspacing="0" border="0">
  <tr>
    <td style="padding-right: 16px;">Item 1</td>
    <td style="padding-right: 16px;">Item 2</td>
    <td>Item 3</td>
  </tr>
</table>

Use padding or margin on child elements instead of gap

Fastmail

Partial

Use padding/margin on child elements instead of gap.

Before (Broken)

before.html

5 lines

<div style="display: flex; gap: 16px;">
  <div>Item 1</div>
  <div>Item 2</div>
  <div>Item 3</div>
</div>

After (Fixed)

fixed.html

8 lines

<table role="presentation" cellpadding="0"
  cellspacing="0" border="0">
  <tr>
    <td style="padding-right: 16px;">Item 1</td>
    <td style="padding-right: 16px;">Item 2</td>
    <td>Item 3</td>
  </tr>
</table>

Use padding or margin on child elements instead of gap

Production guidance for gap

gap is a CSS property. Across the email client matrix, 8 of 21 tracked clients support it fully, 7 only partially, and 6 not at all. The clients most likely to require a workaround for this feature are Outlook (New), Outlook Classic, Yahoo Mail. Each of them needs a tailored fallback. See the per-client examples above for the specific code fix Emailens recommends.

When in doubt, ship a baseline that renders without gap and treat it as progressive enhancement on clients where support is verified. Emailens automatically detects cross-client divergence on this feature when you preview an email, so you can see exactly which template paths break before a campaign goes out.

Related Features

!important accent-color align-items animation aspect-ratio backdrop-filter background background-blend-mode

Check your own HTML for gap

Paste your own, or run the sample below. Analyzed in this page, with no signup and nothing stored.

Zero-Friction Engine Preview

Test your gap layout across 21 email clients

Preview rendering, catch CSS issues, and see how gap displays across Outlook, Gmail, and Apple Mail. Free, no account needed.

Instant live preview · No signup required · 21 email engines

Last tested upstream: Dec 28, 2022 · Last synced by Emailens: Sep 2, 2026

caniemail.com (MIT) records Dec 28, 2022 as the last time gap was tested in a real client, 3 years before this sync. Syncing copies that result forward, it does not re-test it. Carried in @emailens/engine data v0.12.2.