diff --git a/lib/shared/markdown.js b/lib/shared/markdown.js
--- a/lib/shared/markdown.js
+++ b/lib/shared/markdown.js
@@ -252,6 +252,26 @@
 
 const spoilerRegex: RegExp = /^\|\|([^\n]+?)\|\|/g;
 
+function matchSpoiler(): MatchFunction {
+  return (source: string, state: State) => {
+    if (!state.inline) {
+      return null;
+    }
+    return spoilerRegex.exec(source);
+  };
+}
+
+function parseSpoiler(
+  capture: Capture,
+  parse: Parser,
+  state: State,
+): UnTypedASTNode {
+  const content = capture[1];
+  return {
+    content: parse(content, state),
+  };
+}
+
 export {
   paragraphRegex,
   paragraphStripTrailingNewlineRegex,
@@ -272,4 +292,6 @@
   matchList,
   parseList,
   matchMentions,
+  matchSpoiler,
+  parseSpoiler,
 };