box-sizing in Superhuman
Works box-sizing works in Superhuman.
Works in 16 of 21 · not supported in 5
Which clients
- Works
- Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook (New), Outlook iOS, Outlook Android, Outlook for Mac, Apple Mail, Apple Mail iOS, Samsung Mail, Thunderbird, HEY Mail, Proton Mail, Fastmail, Superhuman
- Not supported
- Outlook Classic, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, AOL Mail
The fix for the clients that need it
Needed in 5 of 21: Outlook Classic, Yahoo Mail, Yahoo Mail Android and 2 more.
Account for padding in width manually (no box-sizing)
<div style="width: 300px;">
<div style="padding: 20px;">
Content; padding on inner element
</div>
</div>Show the original
<div style="width: 300px; padding: 20px;
box-sizing: border-box;">
Content; total width stays 300px
</div>A free account opens all 21 clients and keeps your checks for 7 days. Create a free account →
Your next question
- Does resize work in Superhuman?
Works in 1 of 21 · partial in 1 · not supported in 16 · 3 untested
- Does <form> work in Superhuman?
Works in 10 of 21 · partial in 4 · not supported in 7
fix - Does <link> work in Superhuman?
Works in 3 of 21 · not supported in 18
fix - Does <video> work in Superhuman?
Works in 3 of 21 · partial in 2 · not supported in 16
fix - Does @import work in Superhuman?
Works in 4 of 21 · not supported in 17
- Does <audio> work in Superhuman?
Works in 4 of 21 · not supported in 17
Questions
- How many email clients support box-sizing?
- It works in 16 of 21, not supported in 5.
To see what in your email Superhuman does not support, paste the whole email.
No signup · Five clients free, Outlook Classic included · All 21 with an account
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Real captures 14 Oct 2026 on 11 installs · caniemail (MIT) via @emailens/engine 0.18.22 · tested upstream 28 Feb 2019 · data last changed 10 Nov 2026 · Outlook (New) cells are the engine's mapping