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HTML Quiz Practice
Active Recall Drill Session
← Exit Session
Question 1 of 1
medium
HTML
Why must every custom element name contain a hyphen (e.g. `user-card`, not `usercard`)?
A
It's a stylistic convention with no functional requirement
B
The spec reserves all-lowercase-no-hyphen names for current and future native HTML elements, guaranteeing custom elements can never collide with them
C
Hyphens are required for CSS selector performance
D
It's only required in Firefox
Check Answer