diff --git a/app/javascript/mastodon/components/__tests__/__snapshots__/button-test.js.snap b/app/javascript/mastodon/components/__tests__/__snapshots__/button-test.js.snap
index 86fbba917b..bfc091d450 100644
--- a/app/javascript/mastodon/components/__tests__/__snapshots__/button-test.js.snap
+++ b/app/javascript/mastodon/components/__tests__/__snapshots__/button-test.js.snap
@@ -4,6 +4,7 @@ exports[`<Button /> adds class "button-secondary" if props.secondary given 1`] =
 <button
   className="button button-secondary"
   onClick={[Function]}
+  type="button"
 />
 `;
 
@@ -11,6 +12,7 @@ exports[`<Button /> renders a button element 1`] = `
 <button
   className="button"
   onClick={[Function]}
+  type="button"
 />
 `;
 
@@ -19,6 +21,7 @@ exports[`<Button /> renders a disabled attribute if props.disabled given 1`] = `
   className="button"
   disabled={true}
   onClick={[Function]}
+  type="button"
 />
 `;
 
@@ -26,6 +29,7 @@ exports[`<Button /> renders class="button--block" if props.block given 1`] = `
 <button
   className="button button--block"
   onClick={[Function]}
+  type="button"
 />
 `;
 
@@ -33,6 +37,7 @@ exports[`<Button /> renders the children 1`] = `
 <button
   className="button"
   onClick={[Function]}
+  type="button"
 >
   <p>
     children
@@ -44,6 +49,7 @@ exports[`<Button /> renders the given text 1`] = `
 <button
   className="button"
   onClick={[Function]}
+  type="button"
 >
   foo
 </button>
@@ -53,6 +59,7 @@ exports[`<Button /> renders the props.text instead of children 1`] = `
 <button
   className="button"
   onClick={[Function]}
+  type="button"
 >
   foo
 </button>
diff --git a/app/javascript/mastodon/components/button.js b/app/javascript/mastodon/components/button.js
index bcb855c7c1..42ce01f384 100644
--- a/app/javascript/mastodon/components/button.js
+++ b/app/javascript/mastodon/components/button.js
@@ -16,8 +16,12 @@ export default class Button extends React.PureComponent {
     children: PropTypes.node,
   };
 
+  static defaultProps = {
+    type: 'button',
+  };
+
   handleClick = (e) => {
-    if (!this.props.disabled) {
+    if (!this.props.disabled && this.props.onClick) {
       this.props.onClick(e);
     }
   }
diff --git a/app/javascript/mastodon/components/icon_button.js b/app/javascript/mastodon/components/icon_button.js
index 47945c475f..8fd9e10c04 100644
--- a/app/javascript/mastodon/components/icon_button.js
+++ b/app/javascript/mastodon/components/icon_button.js
@@ -141,6 +141,7 @@ export default class IconButton extends React.PureComponent {
 
     return (
       <button
+        type='button'
         aria-label={title}
         aria-pressed={pressed}
         aria-expanded={expanded}
diff --git a/app/javascript/mastodon/components/load_more.js b/app/javascript/mastodon/components/load_more.js
index 389c3e1e11..00e023ca2f 100644
--- a/app/javascript/mastodon/components/load_more.js
+++ b/app/javascript/mastodon/components/load_more.js
@@ -18,7 +18,7 @@ export default class LoadMore extends React.PureComponent {
     const { disabled, visible } = this.props;
 
     return (
-      <button className='load-more' disabled={disabled || !visible} style={{ visibility: visible ? 'visible' : 'hidden' }} onClick={this.props.onClick}>
+      <button type='button' className='load-more' disabled={disabled || !visible} style={{ visibility: visible ? 'visible' : 'hidden' }} onClick={this.props.onClick}>
         <FormattedMessage id='status.load_more' defaultMessage='Load more' />
       </button>
     );
diff --git a/app/javascript/mastodon/features/compose/components/compose_form.js b/app/javascript/mastodon/features/compose/components/compose_form.js
index 9f5c3b3144..6a65f44da3 100644
--- a/app/javascript/mastodon/features/compose/components/compose_form.js
+++ b/app/javascript/mastodon/features/compose/components/compose_form.js
@@ -93,7 +93,7 @@ class ComposeForm extends ImmutablePureComponent {
     return !(isSubmitting || isUploading || isChangingUpload || length(fulltext) > 500 || (isOnlyWhitespace && !anyMedia));
   }
 
-  handleSubmit = () => {
+  handleSubmit = (e) => {
     if (this.props.text !== this.autosuggestTextarea.textarea.value) {
       // Something changed the text inside the textarea (e.g. browser extensions like Grammarly)
       // Update the state to match the current text
@@ -105,6 +105,10 @@ class ComposeForm extends ImmutablePureComponent {
     }
 
     this.props.onSubmit(this.context.router ? this.context.router.history : null);
+
+    if (e) {
+      e.preventDefault();
+    }
   }
 
   onSuggestionsClearRequested = () => {
@@ -217,7 +221,7 @@ class ComposeForm extends ImmutablePureComponent {
     }
 
     return (
-      <form className='compose-form'>
+      <form className='compose-form' onSubmit={this.handleSubmit}>
         <WarningContainer />
 
         <ReplyIndicatorContainer />
@@ -280,9 +284,8 @@ class ComposeForm extends ImmutablePureComponent {
         <div className='compose-form__publish'>
           <div className='compose-form__publish-button-wrapper'>
             <Button
-              type="submit"
+              type='submit'
               text={publishText}
-              onClick={this.handleSubmit}
               disabled={!this.canSubmit()}
               block
             />
diff --git a/app/javascript/mastodon/features/compose/components/emoji_picker_dropdown.js b/app/javascript/mastodon/features/compose/components/emoji_picker_dropdown.js
index f433e4de9f..8cca8af2a8 100644
--- a/app/javascript/mastodon/features/compose/components/emoji_picker_dropdown.js
+++ b/app/javascript/mastodon/features/compose/components/emoji_picker_dropdown.js
@@ -96,12 +96,12 @@ class ModifierPickerMenu extends React.PureComponent {
 
     return (
       <div className='emoji-picker-dropdown__modifiers__menu' style={{ display: active ? 'block' : 'none' }} ref={this.setRef}>
-        <button onClick={this.handleClick} data-index={1}><Emoji emoji='fist' set='twitter' size={22} sheetSize={32} skin={1} backgroundImageFn={backgroundImageFn} /></button>
-        <button onClick={this.handleClick} data-index={2}><Emoji emoji='fist' set='twitter' size={22} sheetSize={32} skin={2} backgroundImageFn={backgroundImageFn} /></button>
-        <button onClick={this.handleClick} data-index={3}><Emoji emoji='fist' set='twitter' size={22} sheetSize={32} skin={3} backgroundImageFn={backgroundImageFn} /></button>
-        <button onClick={this.handleClick} data-index={4}><Emoji emoji='fist' set='twitter' size={22} sheetSize={32} skin={4} backgroundImageFn={backgroundImageFn} /></button>
-        <button onClick={this.handleClick} data-index={5}><Emoji emoji='fist' set='twitter' size={22} sheetSize={32} skin={5} backgroundImageFn={backgroundImageFn} /></button>
-        <button onClick={this.handleClick} data-index={6}><Emoji emoji='fist' set='twitter' size={22} sheetSize={32} skin={6} backgroundImageFn={backgroundImageFn} /></button>
+        <button type='button' onClick={this.handleClick} data-index={1}><Emoji emoji='fist' set='twitter' size={22} sheetSize={32} skin={1} backgroundImageFn={backgroundImageFn} /></button>
+        <button type='button' onClick={this.handleClick} data-index={2}><Emoji emoji='fist' set='twitter' size={22} sheetSize={32} skin={2} backgroundImageFn={backgroundImageFn} /></button>
+        <button type='button' onClick={this.handleClick} data-index={3}><Emoji emoji='fist' set='twitter' size={22} sheetSize={32} skin={3} backgroundImageFn={backgroundImageFn} /></button>
+        <button type='button' onClick={this.handleClick} data-index={4}><Emoji emoji='fist' set='twitter' size={22} sheetSize={32} skin={4} backgroundImageFn={backgroundImageFn} /></button>
+        <button type='button' onClick={this.handleClick} data-index={5}><Emoji emoji='fist' set='twitter' size={22} sheetSize={32} skin={5} backgroundImageFn={backgroundImageFn} /></button>
+        <button type='button' onClick={this.handleClick} data-index={6}><Emoji emoji='fist' set='twitter' size={22} sheetSize={32} skin={6} backgroundImageFn={backgroundImageFn} /></button>
       </div>
     );
   }
diff --git a/app/javascript/mastodon/features/compose/components/language_dropdown.js b/app/javascript/mastodon/features/compose/components/language_dropdown.js
index 0af3db7a46..e48fa60ffb 100644
--- a/app/javascript/mastodon/features/compose/components/language_dropdown.js
+++ b/app/javascript/mastodon/features/compose/components/language_dropdown.js
@@ -227,7 +227,7 @@ class LanguageDropdownMenu extends React.PureComponent {
           <div className={`language-dropdown__dropdown ${placement}`} style={{ ...style, opacity: opacity, transform: mounted ? `scale(${scaleX}, ${scaleY})` : null }} ref={this.setRef}>
             <div className='emoji-mart-search'>
               <input type='search' value={searchValue} onChange={this.handleSearchChange} onKeyDown={this.handleSearchKeyDown} placeholder={intl.formatMessage(messages.search)} autoFocus />
-              <button className='emoji-mart-search-icon' disabled={!isSearching} aria-label={intl.formatMessage(messages.clear)} onClick={this.handleClear}>{!isSearching ? loupeIcon : deleteIcon}</button>
+              <button type='button' className='emoji-mart-search-icon' disabled={!isSearching} aria-label={intl.formatMessage(messages.clear)} onClick={this.handleClear}>{!isSearching ? loupeIcon : deleteIcon}</button>
             </div>
 
             <div className='language-dropdown__dropdown__results emoji-mart-scroll' role='listbox' ref={this.setListRef}>
diff --git a/app/javascript/mastodon/features/compose/components/poll_form.js b/app/javascript/mastodon/features/compose/components/poll_form.js
index db49f90eb4..ede29b8a08 100644
--- a/app/javascript/mastodon/features/compose/components/poll_form.js
+++ b/app/javascript/mastodon/features/compose/components/poll_form.js
@@ -157,7 +157,7 @@ class PollForm extends ImmutablePureComponent {
         </ul>
 
         <div className='poll__footer'>
-          <button disabled={options.size >= 4} className='button button-secondary' onClick={this.handleAddOption}><Icon id='plus' /> <FormattedMessage {...messages.add_option} /></button>
+          <button type='button' disabled={options.size >= 4} className='button button-secondary' onClick={this.handleAddOption}><Icon id='plus' /> <FormattedMessage {...messages.add_option} /></button>
 
           {/* eslint-disable-next-line jsx-a11y/no-onchange */}
           <select value={expiresIn} onChange={this.handleSelectDuration}>
diff --git a/app/javascript/mastodon/features/compose/components/text_icon_button.js b/app/javascript/mastodon/features/compose/components/text_icon_button.js
index cd644b680e..73da32ad5d 100644
--- a/app/javascript/mastodon/features/compose/components/text_icon_button.js
+++ b/app/javascript/mastodon/features/compose/components/text_icon_button.js
@@ -22,6 +22,7 @@ export default class TextIconButton extends React.PureComponent {
 
     return (
       <button
+        type='button'
         title={title}
         aria-label={title}
         className={`text-icon-button ${active ? 'active' : ''}`}
diff --git a/app/javascript/mastodon/features/compose/components/upload.js b/app/javascript/mastodon/features/compose/components/upload.js
index 706824dc71..44bf9a24aa 100644
--- a/app/javascript/mastodon/features/compose/components/upload.js
+++ b/app/javascript/mastodon/features/compose/components/upload.js
@@ -43,13 +43,13 @@ export default class Upload extends ImmutablePureComponent {
           {({ scale }) => (
             <div className='compose-form__upload-thumbnail' style={{ transform: `scale(${scale})`, backgroundImage: `url(${media.get('preview_url')})`, backgroundPosition: `${x}% ${y}%` }}>
               <div className='compose-form__upload__actions'>
-                <button className='icon-button' onClick={this.handleUndoClick}><Icon id='times' /> <FormattedMessage id='upload_form.undo' defaultMessage='Delete' /></button>
-                {!isEditingStatus && (<button className='icon-button' onClick={this.handleFocalPointClick}><Icon id='pencil' /> <FormattedMessage id='upload_form.edit' defaultMessage='Edit' /></button>)}
+                <button type='button' className='icon-button' onClick={this.handleUndoClick}><Icon id='times' /> <FormattedMessage id='upload_form.undo' defaultMessage='Delete' /></button>
+                {!isEditingStatus && (<button type='button' className='icon-button' onClick={this.handleFocalPointClick}><Icon id='pencil' /> <FormattedMessage id='upload_form.edit' defaultMessage='Edit' /></button>)}
               </div>
 
               {(media.get('description') || '').length === 0 && (
                 <div className='compose-form__upload__warning'>
-                  <button className='icon-button' onClick={this.handleFocalPointClick}><Icon id='info-circle' /> <FormattedMessage id='upload_form.description_missing' defaultMessage='No description added' /></button>
+                  <button type='button' className='icon-button' onClick={this.handleFocalPointClick}><Icon id='info-circle' /> <FormattedMessage id='upload_form.description_missing' defaultMessage='No description added' /></button>
                 </div>
               )}
             </div>
diff --git a/app/javascript/mastodon/features/favourites/index.js b/app/javascript/mastodon/features/favourites/index.js
index ad10744dae..66ec6a31b4 100644
--- a/app/javascript/mastodon/features/favourites/index.js
+++ b/app/javascript/mastodon/features/favourites/index.js
@@ -68,7 +68,7 @@ class Favourites extends ImmutablePureComponent {
           showBackButton
           multiColumn={multiColumn}
           extraButton={(
-            <button className='column-header__button' title={intl.formatMessage(messages.refresh)} aria-label={intl.formatMessage(messages.refresh)} onClick={this.handleRefresh}><Icon id='refresh' /></button>
+            <button type='button' className='column-header__button' title={intl.formatMessage(messages.refresh)} aria-label={intl.formatMessage(messages.refresh)} onClick={this.handleRefresh}><Icon id='refresh' /></button>
           )}
         />
 
diff --git a/app/javascript/mastodon/features/filters/select_filter.js b/app/javascript/mastodon/features/filters/select_filter.js
index b5b3545296..b68a5de6cc 100644
--- a/app/javascript/mastodon/features/filters/select_filter.js
+++ b/app/javascript/mastodon/features/filters/select_filter.js
@@ -177,7 +177,7 @@ class SelectFilter extends React.PureComponent {
 
         <div className='emoji-mart-search'>
           <input type='search' value={searchValue} onChange={this.handleSearchChange} onKeyDown={this.handleSearchKeyDown} placeholder={intl.formatMessage(messages.search)} autoFocus />
-          <button className='emoji-mart-search-icon' disabled={!isSearching} aria-label={intl.formatMessage(messages.clear)} onClick={this.handleClear}>{!isSearching ? loupeIcon : deleteIcon}</button>
+          <button type='button' className='emoji-mart-search-icon' disabled={!isSearching} aria-label={intl.formatMessage(messages.clear)} onClick={this.handleClear}>{!isSearching ? loupeIcon : deleteIcon}</button>
         </div>
 
         <div className='language-dropdown__dropdown__results emoji-mart-scroll' role='listbox' ref={this.setListRef}>
diff --git a/app/javascript/mastodon/features/home_timeline/index.js b/app/javascript/mastodon/features/home_timeline/index.js
index 838ed7dd84..749a47e76a 100644
--- a/app/javascript/mastodon/features/home_timeline/index.js
+++ b/app/javascript/mastodon/features/home_timeline/index.js
@@ -126,6 +126,7 @@ class HomeTimeline extends React.PureComponent {
     if (hasAnnouncements) {
       announcementsButton = (
         <button
+          type='button'
           className={classNames('column-header__button', { 'active': showAnnouncements })}
           title={intl.formatMessage(showAnnouncements ? messages.hide_announcements : messages.show_announcements)}
           aria-label={intl.formatMessage(showAnnouncements ? messages.hide_announcements : messages.show_announcements)}
diff --git a/app/javascript/mastodon/features/list_timeline/index.js b/app/javascript/mastodon/features/list_timeline/index.js
index fd9d33df71..f1829d34dd 100644
--- a/app/javascript/mastodon/features/list_timeline/index.js
+++ b/app/javascript/mastodon/features/list_timeline/index.js
@@ -178,11 +178,11 @@ class ListTimeline extends React.PureComponent {
           multiColumn={multiColumn}
         >
           <div className='column-settings__row column-header__links'>
-            <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 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/reblogs/index.js b/app/javascript/mastodon/features/reblogs/index.js
index 70d338ef14..36ca11d1a7 100644
--- a/app/javascript/mastodon/features/reblogs/index.js
+++ b/app/javascript/mastodon/features/reblogs/index.js
@@ -68,7 +68,7 @@ class Reblogs extends ImmutablePureComponent {
           showBackButton
           multiColumn={multiColumn}
           extraButton={(
-            <button className='column-header__button' title={intl.formatMessage(messages.refresh)} aria-label={intl.formatMessage(messages.refresh)} onClick={this.handleRefresh}><Icon id='refresh' /></button>
+            <button type='button' className='column-header__button' title={intl.formatMessage(messages.refresh)} aria-label={intl.formatMessage(messages.refresh)} onClick={this.handleRefresh}><Icon id='refresh' /></button>
           )}
         />
 
diff --git a/app/javascript/mastodon/features/status/components/card.js b/app/javascript/mastodon/features/status/components/card.js
index 3d81bcb29b..82537dd5d9 100644
--- a/app/javascript/mastodon/features/status/components/card.js
+++ b/app/javascript/mastodon/features/status/components/card.js
@@ -247,7 +247,7 @@ export default class Card extends React.PureComponent {
             {revealed && (
               <div className='status-card__actions'>
                 <div>
-                  <button onClick={this.handleEmbedClick}><Icon id={iconVariant} /></button>
+                  <button type='button' onClick={this.handleEmbedClick}><Icon id={iconVariant} /></button>
                   {horizontal && <a href={card.get('url')} target='_blank' rel='noopener noreferrer'><Icon id='external-link' /></a>}
                 </div>
               </div>
diff --git a/app/javascript/mastodon/features/status/index.js b/app/javascript/mastodon/features/status/index.js
index 02f390c6a1..c0ba1f2d61 100644
--- a/app/javascript/mastodon/features/status/index.js
+++ b/app/javascript/mastodon/features/status/index.js
@@ -619,7 +619,7 @@ class Status extends ImmutablePureComponent {
           showBackButton
           multiColumn={multiColumn}
           extraButton={(
-            <button className='column-header__button' title={intl.formatMessage(status.get('hidden') ? messages.revealAll : messages.hideAll)} aria-label={intl.formatMessage(status.get('hidden') ? messages.revealAll : messages.hideAll)} onClick={this.handleToggleAll} aria-pressed={status.get('hidden') ? 'false' : 'true'}><Icon id={status.get('hidden') ? 'eye-slash' : 'eye'} /></button>
+            <button type='button' className='column-header__button' title={intl.formatMessage(status.get('hidden') ? messages.revealAll : messages.hideAll)} aria-label={intl.formatMessage(status.get('hidden') ? messages.revealAll : messages.hideAll)} onClick={this.handleToggleAll} aria-pressed={status.get('hidden') ? 'false' : 'true'}><Icon id={status.get('hidden') ? 'eye-slash' : 'eye'} /></button>
           )}
         />