CSS Properties

background-size

CSS property · 17 supported, 2 partial, 2 unsupported across 21 clients

Client Support

Client	Category	Engine	Support
Gmail	webmail	Gmail Web	Supported
Gmail Android	mobile	Gmail Mobile	Partial
Gmail iOS	mobile	Gmail Mobile	Partial
Outlook 365	webmail	Outlook Web	Supported
Outlook (New)	desktop	Outlook Web	Unsupported
Outlook Classic	desktop	Microsoft Word	Unsupported
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	Supported
Proton Mail	webmail	Proton	Supported
AOL Mail	webmail	AOL	Supported
Fastmail	webmail	Fastmail	Supported
Superhuman	desktop	Blink	Supported

Client-by-client behaviour for background-size

Fully supports background-size (17): Gmail, Outlook 365, Outlook iOS, Outlook Android, Outlook for Mac, Apple Mail, Apple Mail iOS, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, Samsung Mail, Thunderbird, HEY Mail, Proton Mail, AOL Mail, Fastmail, Superhuman.

Partial support (2): Gmail Android, Gmail iOS. Expect rendering quirks unique to each engine. Partial support typically means a subset of values, an ignored shorthand, or sanitizer-specific rewrites.

No support (2): Outlook (New), Outlook Classic. Plan fallbacks for these clients before relying on background-size in production sends.

Fixes & Workarounds

Outlook (New)

Unsupported

Not supported in many clients. Set image dimensions directly.

Before

<td style="background: url('bg.jpg') center/cover no-repeat;">
  Content
</td>

After

<!--[if gte mso 9]>
<v:rect xmlns:v="urn:schemas-microsoft-com:vml" fill="true"
  stroke="false" style="width:600px; height:400px;">
  <v:fill type="frame" src="bg.jpg" />
  <v:textbox inset="0,0,0,0">
<![endif]-->
<td style="background: url('bg.jpg') center/cover no-repeat;
            background-color: #333;">
  Content
</td>
<!--[if gte mso 9]>
  </v:textbox>
</v:rect>
<![endif]-->

Outlook ignores background-size — use VML or sized images

Outlook Classic

Unsupported

Not supported in many clients. Set image dimensions directly.

Before

<td style="background: url('bg.jpg') center/cover no-repeat;">
  Content
</td>

After

<!--[if gte mso 9]>
<v:rect xmlns:v="urn:schemas-microsoft-com:vml" fill="true"
  stroke="false" style="width:600px; height:400px;">
  <v:fill type="frame" src="bg.jpg" />
  <v:textbox inset="0,0,0,0">
<![endif]-->
<td style="background: url('bg.jpg') center/cover no-repeat;
            background-color: #333;">
  Content
</td>
<!--[if gte mso 9]>
  </v:textbox>
</v:rect>
<![endif]-->

Outlook ignores background-size — use VML or sized images

Gmail Android

Partial

Not supported in many clients. Set image dimensions directly.

Before

<td style="background: url('bg.jpg') center/cover no-repeat;">
  Content
</td>

After

<!--[if gte mso 9]>
<v:rect xmlns:v="urn:schemas-microsoft-com:vml" fill="true"
  stroke="false" style="width:600px; height:400px;">
  <v:fill type="frame" src="bg.jpg" />
  <v:textbox inset="0,0,0,0">
<![endif]-->
<td style="background: url('bg.jpg') center/cover no-repeat;
            background-color: #333;">
  Content
</td>
<!--[if gte mso 9]>
  </v:textbox>
</v:rect>
<![endif]-->

Outlook ignores background-size — use VML or sized images

Gmail iOS

Partial

Not supported in many clients. Set image dimensions directly.

Before

<td style="background: url('bg.jpg') center/cover no-repeat;">
  Content
</td>

After

<!--[if gte mso 9]>
<v:rect xmlns:v="urn:schemas-microsoft-com:vml" fill="true"
  stroke="false" style="width:600px; height:400px;">
  <v:fill type="frame" src="bg.jpg" />
  <v:textbox inset="0,0,0,0">
<![endif]-->
<td style="background: url('bg.jpg') center/cover no-repeat;
            background-color: #333;">
  Content
</td>
<!--[if gte mso 9]>
  </v:textbox>
</v:rect>
<![endif]-->

Outlook ignores background-size — use VML or sized images

Production guidance for background-size

background-size is a CSS property. Across the email client matrix, 17 of 15 tracked clients support it fully, 2 only partially, and 2 not at all. The clients most likely to require a workaround for this feature are Outlook (New), Outlook Classic, Gmail Android. 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 background-size 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

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Support data last updated Apr 27, 2026 · synced from caniemail.com via @emailens/engine.