Outlook (New)
The new Outlook for Windows uses a Chromium-based web engine identical to Outlook.com/365, replacing the legacy Word rendering engine. This means dramatically better CSS support — flexbox, grid, border-radius, background images, and most modern CSS properties work correctly. Microsoft is rolling this out as the default Windows mail client.
Microsoft's replacement for classic Outlook on Windows. Uses the same web engine as Outlook.com. Being rolled out to all Windows users — classic Outlook reaches end of life October 2026.
CSS coverage profile for Outlook (New)
Outlook (New) renders with the Outlook Web engine and supports 45 of 251 tracked CSS and HTML features fully, with 24 partially supported and 181 unsupported. That places it in a narrow coverage band.
Most modern CSS is unsupported. This client effectively requires a separate, table-based fallback path for any non-trivial layout.
45
Supported
24
Partial
181
Unsupported
251
Total
Key gotchas in Outlook (New)
position (absolute/fixed)Position properties are partially supported. Use table-based positioning for critical layout elements.
transformCSS transforms are stripped. Pre-render visual effects as images.
animation / transitionCSS animations and transitions are removed. Use static designs.
How Outlook (New) renders email
- New Outlook on Windows shares its rendering engine with Outlook.com web, so any CSS that works in the web client should produce identical results in the desktop app — a major upgrade from the Word-based legacy client.
- CSS animations and transforms are stripped at parse time. Any motion-based brand element should be pre-rendered as a static image fallback.
- Position properties beyond static and relative are partially supported; absolute and fixed are dropped in some layouts. Keep critical visual positioning inside table cells.
- Microsoft's data-ogsc dark-mode attribute applies here as well, mirroring Outlook 365 web behaviour.
Dark mode behaviour in Outlook (New)
Outlook (New) applies partial color inversion in dark mode, similar to Outlook.com. Use [data-ogsc] or [data-ogsb] CSS attribute selectors to override dark mode color changes.
QA checklist for Outlook (New)
- Confirm that any animation or transition in the design has a sensible static fallback for New Outlook.
- Test absolute-positioned overlays — they may collapse in this client even though they work in the modern web Outlook.
- Check rendering of conditional <!--[if mso]> blocks; the new engine ignores them, which is correct behaviour but easy to overlook in mixed templates.
Related clients
HTML Elements40
| Feature | Support |
|---|---|
| <abbr> | Unsupported |
| <acronym> | Unsupported |
| <address> | Supported |
| <audio> | Unsupported |
| <base> | Supported |
| <bdi> | Unsupported |
| <blockquote> | Supported |
| <body> | Supported |
| <code> | Supported |
| <del> | Supported |
| <dfn> | Partial |
| <dialog> | Unsupported |
| <div> | Supported |
| <form> | Unsupported |
| <h1> | Supported |
| <hr> | Supported |
| <img> | Supported |
| <link> | Supported |
| <marquee> | Unsupported |
| <meter> | Unsupported |
| <object> | Unsupported |
| <p> | Supported |
| <picture> | Unsupported |
| <pre> | Supported |
| <progress> | Unsupported |
| <rp> | Unsupported |
| <rt> | Unsupported |
| <ruby> | Unsupported |
| <select> | Unsupported |
| <small> | Supported |
| <span> | Supported |
| <strike> | Supported |
| <strong> | Supported |
| <style> | Partial |
| <svg> | Unsupported |
| <table> | Supported |
| <textarea> | Unsupported |
| <ul> | Partial |
| <video> | Unsupported |
| <wbr> | Unsupported |
CSS At-Rules5
| Feature | Support |
|---|---|
| @font-face | Partial |
| @import | Supported |
| @keyframes | Unsupported |
| @media | Unsupported |
| @supports | Unsupported |
Pseudo-Elements6
| Feature | Support |
|---|---|
| ::after | Unsupported |
| ::before | Unsupported |
| ::first-letter | Unsupported |
| ::first-line | Unsupported |
| ::marker | Unsupported |
| ::placeholder | Unsupported |
Pseudo-Classes & Selectors32
| Feature | Support |
|---|---|
| :adjacent-sibling | Unsupported |
| :attribute-selector | Unsupported |
| :chaining | Unsupported |
| :checked | Unsupported |
| :child-combinator | Unsupported |
| :class-selector | Supported |
| :descendant-combinator | Supported |
| :first-child | Unsupported |
| :first-of-type | Unsupported |
| :focus | Unsupported |
| :general-sibling | Unsupported |
| :grouping | Supported |
| :has | Unsupported |
| :hover | Unsupported |
| :id-selector | Supported |
| :lang | Unsupported |
| :last-child | Unsupported |
| :last-of-type | Unsupported |
| :link | Supported |
| :not | Unsupported |
| :nth-child | Unsupported |
| :nth-last-child | Unsupported |
| :nth-of-type | Unsupported |
| :only-child | Unsupported |
| :only-of-type | Unsupported |
| :target | Unsupported |
| :type-selector | Supported |
| :universal-selector | Unsupported |
| :visited | Unsupported |
| pseudo-class-active | Unsupported |
| pseudo-class-default | Unsupported |
| pseudo-class-nth-last-of-type | Unsupported |
CSS Functions8
| Feature | Support |
|---|---|
| calc | Unsupported |
| clamp | Unsupported |
| conic-gradient | Unsupported |
| fit-content | Unsupported |
| linear-gradient | Unsupported |
| max | Unsupported |
| min | Unsupported |
| radial-gradient | Unsupported |
CSS Properties160
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Try Emailens FreeSupport data last updated Apr 27, 2026 · synced from caniemail.com via @emailens/engine.