diff --git a/app/javascript/mastodon/components/admin/ReportReasonSelector.jsx b/app/javascript/mastodon/components/admin/ReportReasonSelector.jsx
index 58a861fde6b..cd14dac4e32 100644
--- a/app/javascript/mastodon/components/admin/ReportReasonSelector.jsx
+++ b/app/javascript/mastodon/components/admin/ReportReasonSelector.jsx
@@ -33,7 +33,7 @@ class Category extends React.PureComponent {
     const { id, text, disabled, selected, children } = this.props;
 
     return (
-      <div tabIndex='0' role='button' className={classNames('report-reason-selector__category', { selected, disabled })} onClick={this.handleClick}>
+      <div tabIndex={0} role='button' className={classNames('report-reason-selector__category', { selected, disabled })} onClick={this.handleClick}>
         {selected && <input type='hidden' name='report[category]' value={id} />}
 
         <div className='report-reason-selector__category__label'>
@@ -74,7 +74,7 @@ class Rule extends React.PureComponent {
     const { id, text, disabled, selected } = this.props;
 
     return (
-      <div tabIndex='0' role='button' className={classNames('report-reason-selector__rule', { selected, disabled })} onClick={this.handleClick}>
+      <div tabIndex={0} role='button' className={classNames('report-reason-selector__rule', { selected, disabled })} onClick={this.handleClick}>
         <span className={classNames('poll__input', { checkbox: true, active: selected, disabled })} />
         {selected && <input type='hidden' name='report[rule_ids][]' value={id} />}
         {text}
diff --git a/app/javascript/mastodon/components/autosuggest_input.jsx b/app/javascript/mastodon/components/autosuggest_input.jsx
index f9616c58178..a68e2a01b47 100644
--- a/app/javascript/mastodon/components/autosuggest_input.jsx
+++ b/app/javascript/mastodon/components/autosuggest_input.jsx
@@ -180,7 +180,7 @@ export default class AutosuggestInput extends ImmutablePureComponent {
     }
 
     return (
-      <div role='button' tabIndex='0' key={key} data-index={i} className={classNames('autosuggest-textarea__suggestions__item', { selected: i === selectedSuggestion })} onMouseDown={this.onSuggestionClick}>
+      <div role='button' tabIndex={0} key={key} data-index={i} className={classNames('autosuggest-textarea__suggestions__item', { selected: i === selectedSuggestion })} onMouseDown={this.onSuggestionClick}>
         {inner}
       </div>
     );
diff --git a/app/javascript/mastodon/components/autosuggest_textarea.jsx b/app/javascript/mastodon/components/autosuggest_textarea.jsx
index c044912983a..a627bc1ec2b 100644
--- a/app/javascript/mastodon/components/autosuggest_textarea.jsx
+++ b/app/javascript/mastodon/components/autosuggest_textarea.jsx
@@ -186,7 +186,7 @@ export default class AutosuggestTextarea extends ImmutablePureComponent {
     }
 
     return (
-      <div role='button' tabIndex='0' key={key} data-index={i} className={classNames('autosuggest-textarea__suggestions__item', { selected: i === selectedSuggestion })} onMouseDown={this.onSuggestionClick}>
+      <div role='button' tabIndex={0} key={key} data-index={i} className={classNames('autosuggest-textarea__suggestions__item', { selected: i === selectedSuggestion })} onMouseDown={this.onSuggestionClick}>
         {inner}
       </div>
     );
diff --git a/app/javascript/mastodon/components/column_back_button_slim.jsx b/app/javascript/mastodon/components/column_back_button_slim.jsx
index cc8bfb1515b..46ac23736b3 100644
--- a/app/javascript/mastodon/components/column_back_button_slim.jsx
+++ b/app/javascript/mastodon/components/column_back_button_slim.jsx
@@ -8,7 +8,7 @@ export default class ColumnBackButtonSlim extends ColumnBackButton {
   render () {
     return (
       <div className='column-back-button--slim'>
-        <div role='button' tabIndex='0' onClick={this.handleClick} className='column-back-button column-back-button--slim-button'>
+        <div role='button' tabIndex={0} onClick={this.handleClick} className='column-back-button column-back-button--slim-button'>
           <Icon id='chevron-left' className='column-back-button__icon' fixedWidth />
           <FormattedMessage id='column_back_button.label' defaultMessage='Back' />
         </div>
diff --git a/app/javascript/mastodon/components/dropdown_menu.jsx b/app/javascript/mastodon/components/dropdown_menu.jsx
index c04c513fbe4..eaaa72fd835 100644
--- a/app/javascript/mastodon/components/dropdown_menu.jsx
+++ b/app/javascript/mastodon/components/dropdown_menu.jsx
@@ -119,7 +119,7 @@ class DropdownMenu extends React.PureComponent {
 
     return (
       <li className='dropdown-menu__item' key={`${text}-${i}`}>
-        <a href={href} target={target} data-method={method} rel='noopener noreferrer' role='button' tabIndex='0' ref={i === 0 ? this.setFocusRef : null} onClick={this.handleClick} onKeyPress={this.handleItemKeyPress} data-index={i}>
+        <a href={href} target={target} data-method={method} rel='noopener noreferrer' role='button' tabIndex={0} ref={i === 0 ? this.setFocusRef : null} onClick={this.handleClick} onKeyPress={this.handleItemKeyPress} data-index={i}>
           {text}
         </a>
       </li>
diff --git a/app/javascript/mastodon/components/gifv.jsx b/app/javascript/mastodon/components/gifv.jsx
index 9ec201c6cc1..1ce7e7c29bd 100644
--- a/app/javascript/mastodon/components/gifv.jsx
+++ b/app/javascript/mastodon/components/gifv.jsx
@@ -46,7 +46,7 @@ export default class GIFV extends React.PureComponent {
             width={width}
             height={height}
             role='button'
-            tabIndex='0'
+            tabIndex={0}
             aria-label={alt}
             title={alt}
             lang={lang}
@@ -57,7 +57,7 @@ export default class GIFV extends React.PureComponent {
         <video
           src={src}
           role='button'
-          tabIndex='0'
+          tabIndex={0}
           aria-label={alt}
           title={alt}
           lang={lang}
diff --git a/app/javascript/mastodon/components/icon_button.jsx b/app/javascript/mastodon/components/icon_button.jsx
index 00369237301..989cae44014 100644
--- a/app/javascript/mastodon/components/icon_button.jsx
+++ b/app/javascript/mastodon/components/icon_button.jsx
@@ -23,7 +23,7 @@ export default class IconButton extends React.PureComponent {
     inverted: PropTypes.bool,
     animate: PropTypes.bool,
     overlay: PropTypes.bool,
-    tabIndex: PropTypes.string,
+    tabIndex: PropTypes.number,
     counter: PropTypes.number,
     obfuscateCount: PropTypes.bool,
     href: PropTypes.string,
@@ -36,7 +36,7 @@ export default class IconButton extends React.PureComponent {
     disabled: false,
     animate: false,
     overlay: false,
-    tabIndex: '0',
+    tabIndex: 0,
     ariaHidden: false,
   };
 
diff --git a/app/javascript/mastodon/components/intersection_observer_article.jsx b/app/javascript/mastodon/components/intersection_observer_article.jsx
index c2feb003a8b..77957a21da1 100644
--- a/app/javascript/mastodon/components/intersection_observer_article.jsx
+++ b/app/javascript/mastodon/components/intersection_observer_article.jsx
@@ -113,7 +113,7 @@ export default class IntersectionObserverArticle extends React.Component {
           aria-setsize={listLength}
           style={{ height: `${this.height || cachedHeight}px`, opacity: 0, overflow: 'hidden' }}
           data-id={id}
-          tabIndex='0'
+          tabIndex={0}
         >
           {children && React.cloneElement(children, { hidden: true })}
         </article>
@@ -121,7 +121,7 @@ export default class IntersectionObserverArticle extends React.Component {
     }
 
     return (
-      <article ref={this.handleRef} aria-posinset={index + 1} aria-setsize={listLength} data-id={id} tabIndex='0'>
+      <article ref={this.handleRef} aria-posinset={index + 1} aria-setsize={listLength} data-id={id} tabIndex={0}>
         {children && React.cloneElement(children, { hidden: false })}
       </article>
     );
diff --git a/app/javascript/mastodon/components/picture_in_picture_placeholder.jsx b/app/javascript/mastodon/components/picture_in_picture_placeholder.jsx
index c8aa8f75798..6322b1c668a 100644
--- a/app/javascript/mastodon/components/picture_in_picture_placeholder.jsx
+++ b/app/javascript/mastodon/components/picture_in_picture_placeholder.jsx
@@ -58,7 +58,7 @@ class PictureInPicturePlaceholder extends React.PureComponent {
     const { height } = this.state;
 
     return (
-      <div ref={this.setRef} className='picture-in-picture-placeholder' style={{ height }} role='button' tabIndex='0' onClick={this.handleClick}>
+      <div ref={this.setRef} className='picture-in-picture-placeholder' style={{ height }} role='button' tabIndex={0} onClick={this.handleClick}>
         <Icon id='window-restore' />
         <FormattedMessage id='picture_in_picture.restore' defaultMessage='Put it back' />
       </div>
diff --git a/app/javascript/mastodon/components/poll.jsx b/app/javascript/mastodon/components/poll.jsx
index 360557d007c..b9b96a7005b 100644
--- a/app/javascript/mastodon/components/poll.jsx
+++ b/app/javascript/mastodon/components/poll.jsx
@@ -154,7 +154,7 @@ class Poll extends ImmutablePureComponent {
           {!showResults && (
             <span
               className={classNames('poll__input', { checkbox: poll.get('multiple'), active })}
-              tabIndex='0'
+              tabIndex={0}
               role={poll.get('multiple') ? 'checkbox' : 'radio'}
               onKeyPress={this.handleOptionKeyPress}
               aria-checked={active}
diff --git a/app/javascript/mastodon/components/status.jsx b/app/javascript/mastodon/components/status.jsx
index 281e6987434..923dc892dff 100644
--- a/app/javascript/mastodon/components/status.jsx
+++ b/app/javascript/mastodon/components/status.jsx
@@ -337,7 +337,7 @@ class Status extends ImmutablePureComponent {
     if (hidden) {
       return (
         <HotKeys handlers={handlers}>
-          <div ref={this.handleRef} className={classNames('status__wrapper', { focusable: !this.props.muted })} tabIndex='0'>
+          <div ref={this.handleRef} className={classNames('status__wrapper', { focusable: !this.props.muted })} tabIndex={0}>
             <span>{status.getIn(['account', 'display_name']) || status.getIn(['account', 'username'])}</span>
             <span>{status.get('content')}</span>
           </div>
@@ -354,7 +354,7 @@ class Status extends ImmutablePureComponent {
 
       return (
         <HotKeys handlers={minHandlers}>
-          <div className='status__wrapper status__wrapper--filtered focusable' tabIndex='0' ref={this.handleRef}>
+          <div className='status__wrapper status__wrapper--filtered focusable' tabIndex={0} ref={this.handleRef}>
             <FormattedMessage id='status.filtered' defaultMessage='Filtered' />: {matchedFilters.join(', ')}.
             {' '}
             <button className='status__wrapper--filtered__button' onClick={this.handleUnfilterClick}>
diff --git a/app/javascript/mastodon/components/status_content.jsx b/app/javascript/mastodon/components/status_content.jsx
index 8d3a80248db..fb953b9dd86 100644
--- a/app/javascript/mastodon/components/status_content.jsx
+++ b/app/javascript/mastodon/components/status_content.jsx
@@ -268,7 +268,7 @@ class StatusContent extends React.PureComponent {
       }
 
       return (
-        <div className={classNames} ref={this.setRef} tabIndex='0' onMouseDown={this.handleMouseDown} onMouseUp={this.handleMouseUp} onMouseEnter={this.handleMouseEnter} onMouseLeave={this.handleMouseLeave}>
+        <div className={classNames} ref={this.setRef} tabIndex={0} onMouseDown={this.handleMouseDown} onMouseUp={this.handleMouseUp} onMouseEnter={this.handleMouseEnter} onMouseLeave={this.handleMouseLeave}>
           <p style={{ marginBottom: hidden && status.get('mentions').isEmpty() ? '0px' : null }}>
             <span dangerouslySetInnerHTML={spoilerContent} className='translate' lang={lang} />
             {' '}
@@ -286,7 +286,7 @@ class StatusContent extends React.PureComponent {
     } else if (this.props.onClick) {
       return (
         <>
-          <div className={classNames} ref={this.setRef} tabIndex='0' onMouseDown={this.handleMouseDown} onMouseUp={this.handleMouseUp} key='status-content' onMouseEnter={this.handleMouseEnter} onMouseLeave={this.handleMouseLeave}>
+          <div className={classNames} ref={this.setRef} tabIndex={0} onMouseDown={this.handleMouseDown} onMouseUp={this.handleMouseUp} key='status-content' onMouseEnter={this.handleMouseEnter} onMouseLeave={this.handleMouseLeave}>
             <div className='status__content__text status__content__text--visible translate' lang={lang} dangerouslySetInnerHTML={content} />
 
             {poll}
@@ -298,7 +298,7 @@ class StatusContent extends React.PureComponent {
       );
     } else {
       return (
-        <div className={classNames} ref={this.setRef} tabIndex='0' onMouseEnter={this.handleMouseEnter} onMouseLeave={this.handleMouseLeave}>
+        <div className={classNames} ref={this.setRef} tabIndex={0} onMouseEnter={this.handleMouseEnter} onMouseLeave={this.handleMouseLeave}>
           <div className='status__content__text status__content__text--visible translate' lang={lang} dangerouslySetInnerHTML={content} />
 
           {poll}
diff --git a/app/javascript/mastodon/features/about/index.jsx b/app/javascript/mastodon/features/about/index.jsx
index 2804c4a2146..bb35f3203b0 100644
--- a/app/javascript/mastodon/features/about/index.jsx
+++ b/app/javascript/mastodon/features/about/index.jsx
@@ -67,7 +67,7 @@ class Section extends React.PureComponent {
 
     return (
       <div className={classNames('about__section', { active: !collapsed })}>
-        <div className='about__section__title' role='button' tabIndex='0' onClick={this.handleClick}>
+        <div className='about__section__title' role='button' tabIndex={0} onClick={this.handleClick}>
           <Icon id={collapsed ? 'chevron-right' : 'chevron-down'} fixedWidth /> {title}
         </div>
 
diff --git a/app/javascript/mastodon/features/audio/index.jsx b/app/javascript/mastodon/features/audio/index.jsx
index b0c6eeee620..df40b48f00a 100644
--- a/app/javascript/mastodon/features/audio/index.jsx
+++ b/app/javascript/mastodon/features/audio/index.jsx
@@ -470,7 +470,7 @@ class Audio extends React.PureComponent {
     }
 
     return (
-      <div className={classNames('audio-player', { editable, inactive: !revealed })} ref={this.setPlayerRef} style={{ backgroundColor: this._getBackgroundColor(), color: this._getForegroundColor(), width: '100%', height: this.props.fullscreen ? '100%' : (this.state.height || this.props.height) }} onMouseEnter={this.handleMouseEnter} onMouseLeave={this.handleMouseLeave} tabIndex='0' onKeyDown={this.handleKeyDown}>
+      <div className={classNames('audio-player', { editable, inactive: !revealed })} ref={this.setPlayerRef} style={{ backgroundColor: this._getBackgroundColor(), color: this._getForegroundColor(), width: '100%', height: this.props.fullscreen ? '100%' : (this.state.height || this.props.height) }} onMouseEnter={this.handleMouseEnter} onMouseLeave={this.handleMouseLeave} tabIndex={0} onKeyDown={this.handleKeyDown}>
 
         <Blurhash
           hash={blurhash}
@@ -493,7 +493,7 @@ class Audio extends React.PureComponent {
 
         <canvas
           role='button'
-          tabIndex='0'
+          tabIndex={0}
           className='audio-player__canvas'
           width={this.state.width}
           height={this.state.height}
@@ -526,7 +526,7 @@ class Audio extends React.PureComponent {
 
           <span
             className={classNames('video-player__seek__handle', { active: dragging })}
-            tabIndex='0'
+            tabIndex={0}
             style={{ left: `${progress}%`, backgroundColor: this._getAccentColor() }}
             onKeyDown={this.handleAudioKeyDown}
           />
@@ -543,7 +543,7 @@ class Audio extends React.PureComponent {
 
                 <span
                   className='video-player__volume__handle'
-                  tabIndex='0'
+                  tabIndex={0}
                   style={{ left: `${volume * 100}%`, backgroundColor: this._getAccentColor() }}
                 />
               </div>
diff --git a/app/javascript/mastodon/features/compose/components/language_dropdown.jsx b/app/javascript/mastodon/features/compose/components/language_dropdown.jsx
index 908cb61a75d..08542e3a95e 100644
--- a/app/javascript/mastodon/features/compose/components/language_dropdown.jsx
+++ b/app/javascript/mastodon/features/compose/components/language_dropdown.jsx
@@ -209,7 +209,7 @@ class LanguageDropdownMenu extends React.PureComponent {
     const { value } = this.props;
 
     return (
-      <div key={lang[0]} role='option' tabIndex='0' data-index={lang[0]} className={classNames('language-dropdown__dropdown__results__item', { active: lang[0] === value })} aria-selected={lang[0] === value} onClick={this.handleClick} onKeyDown={this.handleKeyDown}>
+      <div key={lang[0]} role='option' tabIndex={0} data-index={lang[0]} className={classNames('language-dropdown__dropdown__results__item', { active: lang[0] === value })} aria-selected={lang[0] === value} onClick={this.handleClick} onKeyDown={this.handleKeyDown}>
         <span className='language-dropdown__dropdown__results__item__native-name' lang={lang[0]}>{lang[2]}</span> <span className='language-dropdown__dropdown__results__item__common-name'>({lang[1]})</span>
       </div>
     );
diff --git a/app/javascript/mastodon/features/compose/components/poll_form.jsx b/app/javascript/mastodon/features/compose/components/poll_form.jsx
index c5a8f8ca7fa..c0acd7eeb9e 100644
--- a/app/javascript/mastodon/features/compose/components/poll_form.jsx
+++ b/app/javascript/mastodon/features/compose/components/poll_form.jsx
@@ -82,7 +82,7 @@ class OptionIntl extends React.PureComponent {
             onClick={this.handleToggleMultiple}
             onKeyPress={this.handleCheckboxKeypress}
             role='button'
-            tabIndex='0'
+            tabIndex={0}
             title={intl.formatMessage(isPollMultiple ? messages.switchToSingle : messages.switchToMultiple)}
             aria-label={intl.formatMessage(isPollMultiple ? messages.switchToSingle : messages.switchToMultiple)}
           />
diff --git a/app/javascript/mastodon/features/compose/components/privacy_dropdown.jsx b/app/javascript/mastodon/features/compose/components/privacy_dropdown.jsx
index 6c4b1064e6d..e65c9cb7261 100644
--- a/app/javascript/mastodon/features/compose/components/privacy_dropdown.jsx
+++ b/app/javascript/mastodon/features/compose/components/privacy_dropdown.jsx
@@ -115,7 +115,7 @@ class PrivacyDropdownMenu extends React.PureComponent {
     return (
       <div style={{ ...style }} role='listbox' ref={this.setRef}>
         {items.map(item => (
-          <div role='option' tabIndex='0' key={item.value} data-index={item.value} onKeyDown={this.handleKeyDown} onClick={this.handleClick} className={classNames('privacy-dropdown__option', { active: item.value === value })} aria-selected={item.value === value} ref={item.value === value ? this.setFocusRef : null}>
+          <div role='option' tabIndex={0} key={item.value} data-index={item.value} onKeyDown={this.handleKeyDown} onClick={this.handleClick} className={classNames('privacy-dropdown__option', { active: item.value === value })} aria-selected={item.value === value} ref={item.value === value ? this.setFocusRef : null}>
             <div className='privacy-dropdown__option__icon'>
               <Icon id={item.icon} fixedWidth />
             </div>
diff --git a/app/javascript/mastodon/features/compose/components/search.jsx b/app/javascript/mastodon/features/compose/components/search.jsx
index 717ecea3709..46723f5cce3 100644
--- a/app/javascript/mastodon/features/compose/components/search.jsx
+++ b/app/javascript/mastodon/features/compose/components/search.jsx
@@ -287,7 +287,7 @@ class Search extends React.PureComponent {
           onBlur={this.handleBlur}
         />
 
-        <div role='button' tabIndex='0' className='search__icon' onClick={this.handleClear}>
+        <div role='button' tabIndex={0} className='search__icon' onClick={this.handleClear}>
           <Icon id='search' className={hasValue ? '' : 'active'} />
           <Icon id='times-circle' className={hasValue ? 'active' : ''} aria-label={intl.formatMessage(messages.placeholder)} />
         </div>
diff --git a/app/javascript/mastodon/features/compose/components/upload.jsx b/app/javascript/mastodon/features/compose/components/upload.jsx
index f114680b93c..e3651c22906 100644
--- a/app/javascript/mastodon/features/compose/components/upload.jsx
+++ b/app/javascript/mastodon/features/compose/components/upload.jsx
@@ -42,7 +42,7 @@ export default class Upload extends ImmutablePureComponent {
     const y = ((focusY / -2) + .5) * 100;
 
     return (
-      <div className='compose-form__upload' tabIndex='0' role='button'>
+      <div className='compose-form__upload' tabIndex={0} role='button'>
         <Motion defaultStyle={{ scale: 0.8 }} style={{ scale: spring(1, { stiffness: 180, damping: 12 }) }}>
           {({ scale }) => (
             <div className='compose-form__upload-thumbnail' style={{ transform: `scale(${scale})`, backgroundImage: `url(${media.get('preview_url')})`, backgroundPosition: `${x}% ${y}%` }}>
diff --git a/app/javascript/mastodon/features/direct_timeline/components/conversation.jsx b/app/javascript/mastodon/features/direct_timeline/components/conversation.jsx
index 5996dd6663f..d0dbffe6591 100644
--- a/app/javascript/mastodon/features/direct_timeline/components/conversation.jsx
+++ b/app/javascript/mastodon/features/direct_timeline/components/conversation.jsx
@@ -144,7 +144,7 @@ class Conversation extends ImmutablePureComponent {
 
     return (
       <HotKeys handlers={handlers}>
-        <div className={classNames('conversation focusable muted', { 'conversation--unread': unread })} tabIndex='0'>
+        <div className={classNames('conversation focusable muted', { 'conversation--unread': unread })} tabIndex={0}>
           <div className='conversation__avatar' onClick={this.handleClick} role='presentation'>
             <AvatarComposite accounts={accounts} size={48} />
           </div>
diff --git a/app/javascript/mastodon/features/filters/select_filter.jsx b/app/javascript/mastodon/features/filters/select_filter.jsx
index b0aede1877e..5778eec8e97 100644
--- a/app/javascript/mastodon/features/filters/select_filter.jsx
+++ b/app/javascript/mastodon/features/filters/select_filter.jsx
@@ -65,7 +65,7 @@ class SelectFilter extends React.PureComponent {
     }
 
     return (
-      <div key={filter[0]} role='button' tabIndex='0' data-index={filter[0]} className='language-dropdown__dropdown__results__item' onClick={this.handleItemClick} onKeyDown={this.handleKeyDown}>
+      <div key={filter[0]} role='button' tabIndex={0} data-index={filter[0]} className='language-dropdown__dropdown__results__item' onClick={this.handleItemClick} onKeyDown={this.handleKeyDown}>
         <span className='language-dropdown__dropdown__results__item__native-name'>{filter[1]}</span> {warning}
       </div>
     );
@@ -73,7 +73,7 @@ class SelectFilter extends React.PureComponent {
 
   renderCreateNew (name) {
     return (
-      <div key='add-new-filter' role='button' tabIndex='0' className='language-dropdown__dropdown__results__item' onClick={this.handleNewFilterClick} onKeyDown={this.handleKeyDown}>
+      <div key='add-new-filter' role='button' tabIndex={0} className='language-dropdown__dropdown__results__item' onClick={this.handleNewFilterClick} onKeyDown={this.handleKeyDown}>
         <Icon id='plus' fixedWidth /> <FormattedMessage id='filter_modal.select_filter.prompt_new' defaultMessage='New category: {name}' values={{ name }} />
       </div>
     );
diff --git a/app/javascript/mastodon/features/list_editor/components/search.jsx b/app/javascript/mastodon/features/list_editor/components/search.jsx
index b9745e0a8be..f70e272f794 100644
--- a/app/javascript/mastodon/features/list_editor/components/search.jsx
+++ b/app/javascript/mastodon/features/list_editor/components/search.jsx
@@ -63,7 +63,7 @@ class Search extends React.PureComponent {
           />
         </label>
 
-        <div role='button' tabIndex='0' className='search__icon' onClick={this.handleClear}>
+        <div role='button' tabIndex={0} className='search__icon' onClick={this.handleClear}>
           <Icon id='search' className={classNames({ active: !hasValue })} />
           <Icon id='times-circle' aria-label={intl.formatMessage(messages.search)} className={classNames({ active: hasValue })} />
         </div>
diff --git a/app/javascript/mastodon/features/list_editor/index.jsx b/app/javascript/mastodon/features/list_editor/index.jsx
index 65cebbdc83c..ed9d091326c 100644
--- a/app/javascript/mastodon/features/list_editor/index.jsx
+++ b/app/javascript/mastodon/features/list_editor/index.jsx
@@ -60,7 +60,7 @@ class ListEditor extends ImmutablePureComponent {
             {accountIds.map(accountId => <Account key={accountId} accountId={accountId} added />)}
           </div>
 
-          {showSearch && <div role='button' tabIndex='-1' className='drawer__backdrop' onClick={onClear} />}
+          {showSearch && <div role='button' tabIndex={-1} className='drawer__backdrop' onClick={onClear} />}
 
           <Motion defaultStyle={{ x: -100 }} style={{ x: spring(showSearch ? 0 : -100, { stiffness: 210, damping: 20 }) }}>
             {({ x }) => (
diff --git a/app/javascript/mastodon/features/list_timeline/index.jsx b/app/javascript/mastodon/features/list_timeline/index.jsx
index d0ba2a186ad..c0b9a62ff9d 100644
--- a/app/javascript/mastodon/features/list_timeline/index.jsx
+++ b/app/javascript/mastodon/features/list_timeline/index.jsx
@@ -176,11 +176,11 @@ class ListTimeline extends React.PureComponent {
           multiColumn={multiColumn}
         >
           <div className='column-settings__row column-header__links'>
-            <button type='button' className='text-btn column-header__setting-btn' tabIndex='0' onClick={this.handleEditClick}>
+            <button type='button' className='text-btn column-header__setting-btn' tabIndex={0} onClick={this.handleEditClick}>
               <Icon id='pencil' /> <FormattedMessage id='lists.edit' defaultMessage='Edit list' />
             </button>
 
-            <button type='button' className='text-btn column-header__setting-btn' tabIndex='0' onClick={this.handleDeleteClick}>
+            <button type='button' className='text-btn column-header__setting-btn' tabIndex={0} onClick={this.handleDeleteClick}>
               <Icon id='trash' /> <FormattedMessage id='lists.delete' defaultMessage='Delete list' />
             </button>
           </div>
diff --git a/app/javascript/mastodon/features/notifications/components/clear_column_button.jsx b/app/javascript/mastodon/features/notifications/components/clear_column_button.jsx
index b82fd092f8e..9a076ce5edb 100644
--- a/app/javascript/mastodon/features/notifications/components/clear_column_button.jsx
+++ b/app/javascript/mastodon/features/notifications/components/clear_column_button.jsx
@@ -11,7 +11,7 @@ export default class ClearColumnButton extends React.PureComponent {
 
   render () {
     return (
-      <button className='text-btn column-header__setting-btn' tabIndex='0' onClick={this.props.onClick}><Icon id='eraser' /> <FormattedMessage id='notifications.clear' defaultMessage='Clear notifications' /></button>
+      <button className='text-btn column-header__setting-btn' tabIndex={0} onClick={this.props.onClick}><Icon id='eraser' /> <FormattedMessage id='notifications.clear' defaultMessage='Clear notifications' /></button>
     );
   }
 
diff --git a/app/javascript/mastodon/features/notifications/components/grant_permission_button.jsx b/app/javascript/mastodon/features/notifications/components/grant_permission_button.jsx
index 798e4c7872b..5b2db48fdbd 100644
--- a/app/javascript/mastodon/features/notifications/components/grant_permission_button.jsx
+++ b/app/javascript/mastodon/features/notifications/components/grant_permission_button.jsx
@@ -10,7 +10,7 @@ export default class GrantPermissionButton extends React.PureComponent {
 
   render () {
     return (
-      <button className='text-btn column-header__permission-btn' tabIndex='0' onClick={this.props.onClick}>
+      <button className='text-btn column-header__permission-btn' tabIndex={0} onClick={this.props.onClick}>
         <FormattedMessage id='notifications.grant_permission' defaultMessage='Grant permission.' />
       </button>
     );
diff --git a/app/javascript/mastodon/features/notifications/components/notification.jsx b/app/javascript/mastodon/features/notifications/components/notification.jsx
index cf9d9f72c90..f3104cee055 100644
--- a/app/javascript/mastodon/features/notifications/components/notification.jsx
+++ b/app/javascript/mastodon/features/notifications/components/notification.jsx
@@ -123,7 +123,7 @@ class Notification extends ImmutablePureComponent {
 
     return (
       <HotKeys handlers={this.getHandlers()}>
-        <div className={classNames('notification notification-follow focusable', { unread })} tabIndex='0' aria-label={notificationForScreenReader(intl, intl.formatMessage(messages.follow, { name: account.get('acct') }), notification.get('created_at'))}>
+        <div className={classNames('notification notification-follow focusable', { unread })} tabIndex={0} aria-label={notificationForScreenReader(intl, intl.formatMessage(messages.follow, { name: account.get('acct') }), notification.get('created_at'))}>
           <div className='notification__message'>
             <div className='notification__favourite-icon-wrapper'>
               <Icon id='user-plus' fixedWidth />
@@ -145,7 +145,7 @@ class Notification extends ImmutablePureComponent {
 
     return (
       <HotKeys handlers={this.getHandlers()}>
-        <div className={classNames('notification notification-follow-request focusable', { unread })} tabIndex='0' aria-label={notificationForScreenReader(intl, intl.formatMessage({ id: 'notification.follow_request', defaultMessage: '{name} has requested to follow you' }, { name: account.get('acct') }), notification.get('created_at'))}>
+        <div className={classNames('notification notification-follow-request focusable', { unread })} tabIndex={0} aria-label={notificationForScreenReader(intl, intl.formatMessage({ id: 'notification.follow_request', defaultMessage: '{name} has requested to follow you' }, { name: account.get('acct') }), notification.get('created_at'))}>
           <div className='notification__message'>
             <div className='notification__favourite-icon-wrapper'>
               <Icon id='user' fixedWidth />
@@ -185,7 +185,7 @@ class Notification extends ImmutablePureComponent {
 
     return (
       <HotKeys handlers={this.getHandlers()}>
-        <div className={classNames('notification notification-favourite focusable', { unread })} tabIndex='0' aria-label={notificationForScreenReader(intl, intl.formatMessage(messages.favourite, { name: notification.getIn(['account', 'acct']) }), notification.get('created_at'))}>
+        <div className={classNames('notification notification-favourite focusable', { unread })} tabIndex={0} aria-label={notificationForScreenReader(intl, intl.formatMessage(messages.favourite, { name: notification.getIn(['account', 'acct']) }), notification.get('created_at'))}>
           <div className='notification__message'>
             <div className='notification__favourite-icon-wrapper'>
               <Icon id='star' className='star-icon' fixedWidth />
@@ -217,7 +217,7 @@ class Notification extends ImmutablePureComponent {
 
     return (
       <HotKeys handlers={this.getHandlers()}>
-        <div className={classNames('notification notification-reblog focusable', { unread })} tabIndex='0' aria-label={notificationForScreenReader(intl, intl.formatMessage(messages.reblog, { name: notification.getIn(['account', 'acct']) }), notification.get('created_at'))}>
+        <div className={classNames('notification notification-reblog focusable', { unread })} tabIndex={0} aria-label={notificationForScreenReader(intl, intl.formatMessage(messages.reblog, { name: notification.getIn(['account', 'acct']) }), notification.get('created_at'))}>
           <div className='notification__message'>
             <div className='notification__favourite-icon-wrapper'>
               <Icon id='retweet' fixedWidth />
@@ -253,7 +253,7 @@ class Notification extends ImmutablePureComponent {
 
     return (
       <HotKeys handlers={this.getHandlers()}>
-        <div className={classNames('notification notification-status focusable', { unread })} tabIndex='0' aria-label={notificationForScreenReader(intl, intl.formatMessage(messages.status, { name: notification.getIn(['account', 'acct']) }), notification.get('created_at'))}>
+        <div className={classNames('notification notification-status focusable', { unread })} tabIndex={0} aria-label={notificationForScreenReader(intl, intl.formatMessage(messages.status, { name: notification.getIn(['account', 'acct']) }), notification.get('created_at'))}>
           <div className='notification__message'>
             <div className='notification__favourite-icon-wrapper'>
               <Icon id='home' fixedWidth />
@@ -290,7 +290,7 @@ class Notification extends ImmutablePureComponent {
 
     return (
       <HotKeys handlers={this.getHandlers()}>
-        <div className={classNames('notification notification-update focusable', { unread })} tabIndex='0' aria-label={notificationForScreenReader(intl, intl.formatMessage(messages.update, { name: notification.getIn(['account', 'acct']) }), notification.get('created_at'))}>
+        <div className={classNames('notification notification-update focusable', { unread })} tabIndex={0} aria-label={notificationForScreenReader(intl, intl.formatMessage(messages.update, { name: notification.getIn(['account', 'acct']) }), notification.get('created_at'))}>
           <div className='notification__message'>
             <div className='notification__favourite-icon-wrapper'>
               <Icon id='pencil' fixedWidth />
@@ -329,7 +329,7 @@ class Notification extends ImmutablePureComponent {
 
     return (
       <HotKeys handlers={this.getHandlers()}>
-        <div className={classNames('notification notification-poll focusable', { unread })} tabIndex='0' aria-label={notificationForScreenReader(intl, message, notification.get('created_at'))}>
+        <div className={classNames('notification notification-poll focusable', { unread })} tabIndex={0} aria-label={notificationForScreenReader(intl, message, notification.get('created_at'))}>
           <div className='notification__message'>
             <div className='notification__favourite-icon-wrapper'>
               <Icon id='tasks' fixedWidth />
@@ -366,7 +366,7 @@ class Notification extends ImmutablePureComponent {
 
     return (
       <HotKeys handlers={this.getHandlers()}>
-        <div className={classNames('notification notification-admin-sign-up focusable', { unread })} tabIndex='0' aria-label={notificationForScreenReader(intl, intl.formatMessage(messages.adminSignUp, { name: account.get('acct') }), notification.get('created_at'))}>
+        <div className={classNames('notification notification-admin-sign-up focusable', { unread })} tabIndex={0} aria-label={notificationForScreenReader(intl, intl.formatMessage(messages.adminSignUp, { name: account.get('acct') }), notification.get('created_at'))}>
           <div className='notification__message'>
             <div className='notification__favourite-icon-wrapper'>
               <Icon id='user-plus' fixedWidth />
@@ -396,7 +396,7 @@ class Notification extends ImmutablePureComponent {
 
     return (
       <HotKeys handlers={this.getHandlers()}>
-        <div className={classNames('notification notification-admin-report focusable', { unread })} tabIndex='0' aria-label={notificationForScreenReader(intl, intl.formatMessage(messages.adminReport, { name: account.get('acct'), target: notification.getIn(['report', 'target_account', 'acct']) }), notification.get('created_at'))}>
+        <div className={classNames('notification notification-admin-report focusable', { unread })} tabIndex={0} aria-label={notificationForScreenReader(intl, intl.formatMessage(messages.adminReport, { name: account.get('acct'), target: notification.getIn(['report', 'target_account', 'acct']) }), notification.get('created_at'))}>
           <div className='notification__message'>
             <div className='notification__favourite-icon-wrapper'>
               <Icon id='flag' fixedWidth />
diff --git a/app/javascript/mastodon/features/report/components/option.jsx b/app/javascript/mastodon/features/report/components/option.jsx
index 42c04b018a2..342204e22f2 100644
--- a/app/javascript/mastodon/features/report/components/option.jsx
+++ b/app/javascript/mastodon/features/report/components/option.jsx
@@ -40,7 +40,7 @@ export default class Option extends React.PureComponent {
 
         <span
           className={classNames('poll__input', { active: checked, checkbox: multiple })}
-          tabIndex='0'
+          tabIndex={0}
           role='radio'
           onKeyPress={this.handleKeyPress}
           aria-checked={checked}
diff --git a/app/javascript/mastodon/features/status/index.jsx b/app/javascript/mastodon/features/status/index.jsx
index 1d7cb685f2c..2d18c6e9d9a 100644
--- a/app/javascript/mastodon/features/status/index.jsx
+++ b/app/javascript/mastodon/features/status/index.jsx
@@ -630,7 +630,7 @@ class Status extends ImmutablePureComponent {
             {ancestors}
 
             <HotKeys handlers={handlers}>
-              <div className={classNames('focusable', 'detailed-status__wrapper', `detailed-status__wrapper-${status.get('visibility')}`)} tabIndex='0' aria-label={textForScreenReader(intl, status, false)}>
+              <div className={classNames('focusable', 'detailed-status__wrapper', `detailed-status__wrapper-${status.get('visibility')}`)} tabIndex={0} aria-label={textForScreenReader(intl, status, false)}>
                 <DetailedStatus
                   key={`details-${status.get('id')}`}
                   status={status}
diff --git a/app/javascript/mastodon/features/ui/components/actions_modal.jsx b/app/javascript/mastodon/features/ui/components/actions_modal.jsx
index fd59c1e2060..35090e24266 100644
--- a/app/javascript/mastodon/features/ui/components/actions_modal.jsx
+++ b/app/javascript/mastodon/features/ui/components/actions_modal.jsx
@@ -23,7 +23,7 @@ export default class ActionsModal extends ImmutablePureComponent {
     return (
       <li key={`${text}-${i}`}>
         <a href={href} target='_blank' rel='noopener noreferrer' onClick={this.props.onClick} data-index={i} className={classNames({ active })}>
-          {icon && <IconButton title={text} icon={icon} role='presentation' tabIndex='-1' inverted />}
+          {icon && <IconButton title={text} icon={icon} role='presentation' tabIndex={-1} inverted />}
           <div>
             <div className={classNames({ 'actions-modal__item-label': !!meta })}>{text}</div>
             <div>{meta}</div>
diff --git a/app/javascript/mastodon/features/ui/components/media_modal.jsx b/app/javascript/mastodon/features/ui/components/media_modal.jsx
index aa179a96561..52bd7545353 100644
--- a/app/javascript/mastodon/features/ui/components/media_modal.jsx
+++ b/app/javascript/mastodon/features/ui/components/media_modal.jsx
@@ -138,8 +138,8 @@ class MediaModal extends ImmutablePureComponent {
 
     const index = this.getIndex();
 
-    const leftNav  = media.size > 1 && <button tabIndex='0' className='media-modal__nav media-modal__nav--left' onClick={this.handlePrevClick} aria-label={intl.formatMessage(messages.previous)}><Icon id='chevron-left' fixedWidth /></button>;
-    const rightNav = media.size > 1 && <button tabIndex='0' className='media-modal__nav  media-modal__nav--right' onClick={this.handleNextClick} aria-label={intl.formatMessage(messages.next)}><Icon id='chevron-right' fixedWidth /></button>;
+    const leftNav  = media.size > 1 && <button tabIndex={0} className='media-modal__nav media-modal__nav--left' onClick={this.handlePrevClick} aria-label={intl.formatMessage(messages.previous)}><Icon id='chevron-left' fixedWidth /></button>;
+    const rightNav = media.size > 1 && <button tabIndex={0} className='media-modal__nav  media-modal__nav--right' onClick={this.handleNextClick} aria-label={intl.formatMessage(messages.next)}><Icon id='chevron-right' fixedWidth /></button>;
 
     const content = media.map((image) => {
       const width  = image.getIn(['meta', 'original', 'width']) || null;
diff --git a/app/javascript/mastodon/features/video/index.jsx b/app/javascript/mastodon/features/video/index.jsx
index 58bb45908b1..e2637e0bef7 100644
--- a/app/javascript/mastodon/features/video/index.jsx
+++ b/app/javascript/mastodon/features/video/index.jsx
@@ -582,7 +582,7 @@ class Video extends React.PureComponent {
           poster={preview}
           preload={preload}
           role='button'
-          tabIndex='0'
+          tabIndex={0}
           aria-label={alt}
           title={alt}
           lang={lang}
@@ -611,7 +611,7 @@ class Video extends React.PureComponent {
 
             <span
               className={classNames('video-player__seek__handle', { active: dragging })}
-              tabIndex='0'
+              tabIndex={0}
               style={{ left: `${progress}%` }}
               onKeyDown={this.handleVideoKeyDown}
             />
@@ -627,7 +627,7 @@ class Video extends React.PureComponent {
 
                 <span
                   className={classNames('video-player__volume__handle')}
-                  tabIndex='0'
+                  tabIndex={0}
                   style={{ left: `${volume * 100}%` }}
                 />
               </div>