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Write CSS rules for Firefox only

Written byPhuoc Nguyen
04 Mar, 2021
If you want to add a few CSS rules that fix issues on Firefox only, then this trick might be useful. It introduces two ways to detect Firefox:
@-moz-document url-prefix() {
h1 {
color: blue;

/* Or use `@support` */
@supports (-moz-appearance: none) {
h1 {
color: blue;
The sample code above will add the blue color to `h1` on Firefox.

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