wagtail/client/scss/components/_header.scss

header {
    padding-top: 1em;
    padding-bottom: 1em;
    background-color: $color-header-bg;
    margin-bottom: 2em;
    color: $color-white;

    a {
        color: $color-white;
    }

    h1,
    h2 {
        margin: 0;
        color: $color-white;
    }

    h1 {
        padding: 0.2em 0;

        &.icon:before {
            width: 1em;
            display: none;
            margin-right: 0.4em;
            font-size: 1.5em;
        }
    }

    .col {
        float: left;
        margin-right: 2em;
    }

    .left {
        float: left;

        .hasform &:first-child {
            padding-bottom: 0.5em;
            float: none;
        }
    }

    .right {
        text-align: right;
        float: right;
    }

    // For case where content below header should merge with it
    &.merged {
        margin-bottom: 0;
    }

    &.tab-merged,
    &.no-border {
        border: 0;

        @include media-breakpoint-down(xs) {
            // To all hamburger menu to be visible
            padding-left: $desktop-nice-padding;
            padding-top: 11px;
        }

    }

    &.merged.no-border {
        padding-bottom: 0;
    }

    &.no-v-padding {
        padding-top: 0;
        padding-bottom: 0;
    }

    .button {
        background-color: $color-teal-darker;

        &:hover {
            background-color: $color-teal-dark;
        }
    }

    label {
        @include visuallyhidden();
    }

    input[type=text],
    select {
        border-width: 0;

        &:focus {
            background-color: $color-white;
        }
    }

    .error-message {
        color: inherit;
    }

    .fields {
        margin-top: -0.5em;

        li {
            padding-bottom: 0;
        }

        .field {
            padding: 0;
        }
    }

    .field-content {
        width: auto;
        padding: 0;
    }
}

@include media-breakpoint-up(sm) {
    header {
        padding-top: 1.5em;
        padding-bottom: 1.5em;

        .left {
            float: left;
            margin-right: 0;

            &:first-child {
                padding-bottom: 0;
                float: left;
            }
        }

        .second {
            clear: none;

            .right,
            .left {
                float: right;
            }
        }

        h1.icon:before {
            display: inline-block;
        }

        .col3 {
            @include column(3);
        }

        .col3.actionbutton {
            width: auto;
        }

        .col6 {
            @include column(6);
        }

        .col9 {
            @include column(9);
        }
    }
}

.header-title {
    @include media-breakpoint-down(xs) {
        padding-left: $mobile-nav-indent;
    }
}