Proton Mail
CSS coverage profile for Proton Mail
Proton Mail renders with the Proton engine and supports 198 of 298 tracked CSS and HTML features fully, with 18 partially supported and 82 unsupported. That places it in a moderate coverage band.
A meaningful portion of CSS is unsupported or partially supported. Plan fallbacks for layout-critical features and validate every template before send.
198
Supported
18
Partial
82
Unsupported
298
Total
Breaks here, works nearly everywhere else
18 features that Proton Mail drops while most other clients render them. This is usually what is behind an email that looks correct everywhere but here.
- min-height 18
- :class-selector 17
- :descendant-combinator 17
- :grouping 17
- :id-selector 17
- :type-selector 17
- text-decoration 16
- <input type="checkbox"> 15
- <input type="hidden"> 15
- <input type="radio"> 15
- image-maps 15
- :adjacent-sibling 15
- :child-combinator 15
- :general-sibling 15
- :link 15
- :universal-selector 15
- <input type="reset"> 14
- :chaining 14
Renders here, dropped almost everywhere else
Safe in Proton Mail and almost nowhere else, so it needs a fallback the moment the send is not Proton Mail-only.
Where Proton Mail is weakest
- Pseudo-Classes & Selectors 28
- CSS Properties 25
- HTML Elements 20
- CSS At-Rules 9
- HTML Attributes 6
Closest client: Superhuman
Superhuman agrees with Proton Mail on 79% of verified features. They still differ on 20: <picture>, <style>, @font-face, @keyframes, @media, @supports, and 14 more.
Side by side
HTML Elements48
| Feature | Support |
|---|---|
| <abbr> | Supported |
| <acronym> | Supported |
| <address> | Supported |
| <audio> | Unsupported |
| <base> | Unsupported |
| <bdi> | Supported |
| <blockquote> | Supported |
| <body> | Unsupported |
| <button type="reset"> | Unsupported |
| <button type="submit"> | Unsupported |
| <code> | Supported |
| <del> | Supported |
| <dfn> | Supported |
| <dialog> | Unsupported |
| <div> | Supported |
| <form> | Unsupported |
| <h1> | Supported |
| <hr> | Supported |
| <img> | Supported |
| <input type="checkbox"> | Unsupported |
| <input type="hidden"> | Unsupported |
| <input type="radio"> | Unsupported |
| <input type="reset"> | Unsupported |
| <input type="submit"> | Unsupported |
| <input type="text"> | Unsupported |
| <link> | Unsupported |
| <marquee> | Partial |
| <meter> | Supported |
| <object> | Unsupported |
| <p> | Supported |
| <picture> | Unsupported |
| <pre> | Supported |
| <progress> | Supported |
| <rp> | Supported |
| <rt> | Supported |
| <ruby> | Supported |
| <select> | Supported |
| <small> | Supported |
| <span> | Supported |
| <strike> | Supported |
| <strong> | Supported |
| <style> | Partial |
| <svg> | Supported |
| <table> | Supported |
| <textarea> | Partial |
| <ul> | Supported |
| <video> | Unsupported |
| <wbr> | Supported |
HTML Attributes22
| Feature | Support |
|---|---|
| [align] | Partial |
| [aria-describedby] | Supported |
| [aria-hidden] | Supported |
| [aria-label] | Supported |
| [aria-labelledby] | Supported |
| [aria-live] | Supported |
| [background] | Supported |
| [cellpadding] | Supported |
| [cellspacing] | Supported |
| [command] | Unsupported |
| [dir] | Supported |
| [height] | Supported |
| [hidden] | Supported |
| [lang] | Supported |
| [loading] | Unsupported |
| [popover] | Supported |
| [required] | Unsupported |
| [role] | Supported |
| [srcset] | Unsupported |
| [target] | Unsupported |
| [valign] | Supported |
| [width] | Supported |
HTML & Email Structure8
| Feature | Support |
|---|---|
| amp4email | Unsupported |
| anchor-links | Unsupported |
| doctype | Unsupported |
| html-comments | Supported |
| html5-semantics | Supported |
| image-maps | Unsupported |
| mailto-links | Partial |
| meta-color-scheme | Unsupported |
CSS At-Rules10
| Feature | Support |
|---|---|
| @font-face | Unsupported |
| @import | Unsupported |
| @keyframes | Unsupported |
| @media | Partial |
| @media device-pixel-ratio | Unsupported |
| @media hover | Supported |
| @media orientation | Unsupported |
| @media prefers-color-scheme | Unsupported |
| @media prefers-reduced-motion | Partial |
| @supports | Unsupported |
Pseudo-Elements6
| Feature | Support |
|---|---|
| ::after | Unsupported |
| ::before | Unsupported |
| ::first-letter | Unsupported |
| ::first-line | Unsupported |
| ::marker | Unsupported |
| ::placeholder | Unsupported |
Pseudo-Classes & Selectors34
| Feature | Support |
|---|---|
| :adjacent-sibling | Unsupported |
| :attribute-selector | Unsupported |
| :chaining | Unsupported |
| :checked | Unsupported |
| :child-combinator | Unsupported |
| :class-selector | Unsupported |
| :descendant-combinator | Unsupported |
| :first-child | Unsupported |
| :first-of-type | Unsupported |
| :focus | Supported |
| :focus-visible | Supported |
| :focus-within | Supported |
| :general-sibling | Unsupported |
| :grouping | Unsupported |
| :has | Unsupported |
| :hover | Supported |
| :id-selector | Unsupported |
| :lang | Supported |
| :last-child | Unsupported |
| :last-of-type | Unsupported |
| :link | Unsupported |
| :not | Unsupported |
| :nth-child | Unsupported |
| :nth-last-child | Unsupported |
| :nth-of-type | Unsupported |
| :only-child | Unsupported |
| :only-of-type | Unsupported |
| :target | Unsupported |
| :type-selector | Unsupported |
| :universal-selector | Unsupported |
| :visited | Unsupported |
| pseudo-class-active | Supported |
| pseudo-class-default | Unsupported |
| pseudo-class-nth-last-of-type | Unsupported |
CSS Functions8
| Feature | Support |
|---|---|
| calc | Supported |
| clamp | Supported |
| conic-gradient | Supported |
| fit-content | Supported |
| linear-gradient | Supported |
| max | Supported |
| min | Supported |
| radial-gradient | Supported |
CSS Properties162
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Support data last updated Sep 2, 2026 - synced from caniemail.com (MIT) via @emailens/engine.