Custom blocking rules for websites I use.

Twitter-uBlock.txt

! Twitter element block rules, for use in uBlock Origin -------------------------
! ads ---------------------------------------------------------------------------
twitter.com##div.suggested-tweet-stream-container
twitter.com##div.promoted-tweet
twitter.com##li.promoted-trend
twitter.com##div.Footer-adsModule
twitter.com##div.js-actionable-user.promoted-account

! timeline breakers -------------------------------------------------------------
twitter.com##.js-stream-item[data-suggestion-json*='RecycledTweetInline']
twitter.com##.js-stream-item[data-suggestion-json*='ActivityTweet']
twitter.com##li[data-component-context="suggest_recap"]
twitter.com##li[data-component-context="suggest_activity"]
twitter.com##li[data-component-context="suggest_recycled_tweet"]
twitter.com##li[data-component-context="suggest_who_to_follow"]
twitter.com##li.PromptbirdPrompt-streamItem
twitter.com##.js-stream-item.DismissibleModule.separated-module

! misc. annoyances ---------------------------------------------------------------
twitter.com###message-drawer
twitter.com###dashboard-profile-prompt
twitter.com##div.eu-cookie-notice
twitter.com##.under-tweet-translate
twitter.com##.translate-button
twitter.com##div.MomentMakerHomeModule

Twitter-userstyle.css

@-moz-document domain("twitter.com") {
#brand_bar ~ div.toast {
    display: none!important;
}
.GalleryTweet.enable-fade {
    display: none;
}
.flex-module.import-prompt {
    display: none;
}

/* enable image context menu */
.GalleryNav.GalleryNav--next,
.GalleryNav.GalleryNav--prev {
    width: 25% !important;
}
#toggleGifsOverlay {
    left: 0;
}
.UserSmallListItem .content {
    overflow: hidden;
}
/* hide long names */
.DMConversation-scrollContainer {
    overflow-x: auto;
    height: 600px;
}
/* no rounded corners on tweets after timeline breakers */
.js-stream-item.DismissibleModule.separated-module + .stream-item {
    border-top-left-radius: 0;
    border-top-right-radius: 0;
    border-top: 0 none;
}
}

YouTube-uBlock.txt

! YouTube element block rules, for use in uBlock Origin -------------------------
! annoyances --------------------------------------------------------------------
www.youtube.com##.ytp-scroll-min.ytp-pause-overlay
www.youtube.com##.ytp-button.ytp-cards-button
www.youtube.com##.ytp-cards-teaser
www.youtube-nocookie.com##.ytp-scroll-min.ytp-pause-overlay
www.youtube-nocookie.com##.ytp-button.ytp-cards-button
www.youtube-nocookie.com##.ytp-cards-teaser