diff --git a/frontend/__tests__/utils/strings.spec.ts b/frontend/__tests__/utils/strings.spec.ts
index 01bcd6f441b1..3f41799a6ee4 100644
--- a/frontend/__tests__/utils/strings.spec.ts
+++ b/frontend/__tests__/utils/strings.spec.ts
@@ -591,6 +591,78 @@ describe("string utils", () => {
     });
   });
 
+  describe("stripMarkdown", () => {
+    it.each([
+      // Headings
+      ["# Heading 1", "Heading 1", "heading 1"],
+      ["## Heading 2", "Heading 2", "heading 2"],
+      ["###### Heading 6", "Heading 6", "heading 6"],
+      // Bold (only 2+ consecutive markers are formatting)
+      ["**bold** text", "bold text", "double asterisk bold"],
+      ["__bold__ text", "bold text", "double underscore bold"],
+      // Bold + italic (3+ consecutive)
+      ["***bold italic***", "bold italic", "triple asterisk bold italic"],
+      // Single * or _ are NOT stripped (literal punctuation)
+      ["a *b* c", "a *b* c", "single asterisk is literal"],
+      ["a _b_ c", "a _b_ c", "single underscore is literal"],
+      // Links (keep text, remove URL)
+      ["[click here](https://example.com)", "click here", "link"],
+      // Images (keep alt text)
+      ["![alt text](image.png)", "alt text", "image"],
+      // Inline code
+      ["use `console.log` here", "use console.log here", "inline code"],
+      // Code blocks (remove entirely)
+      [
+        "some text\n```\ncode block\n```\nmore text",
+        "some text\nmore text",
+        "code block",
+      ],
+      // Blockquotes
+      ["> quoted text", "quoted text", "blockquote"],
+      // Horizontal rules
+      ["before\n---\nafter", "before\nafter", "horizontal rule (dash)"],
+      ["before\n***\nafter", "before\nafter", "horizontal rule (asterisk)"],
+      // List markers
+      [
+        "- item 1\n- item 2\n- item 3",
+        "item 1\nitem 2\nitem 3",
+        "unordered list",
+      ],
+      ["1. first\n2. second\n3. third", "first\nsecond\nthird", "ordered list"],
+      // HTML tags
+      ["<p>paragraph</p>", "paragraph", "HTML tags"],
+      // Mixed markdown
+      [
+        "# Hello\n\nThis is **bold** and italic.\n\n[link](url)\n\n```\ncode\n```\n\n> quote\n\n---\n\n- list item",
+        "Hello\nThis is bold and italic.\nlink\nquote\nlist item",
+        "mixed markdown",
+      ],
+      // Strikethrough
+      ["~~deleted~~ text", "deleted text", "strikethrough"],
+      // Task lists
+      ["- [ ] unchecked\n- [x] checked", "unchecked\nchecked", "task list"],
+      // Tables (pipe characters removed, separator line remains)
+      [
+        "| Header | Header |\n| ------ | ------ |\n| Cell   | Cell   |",
+        "Header Header \n ------ ------ \n Cell Cell",
+        "table",
+      ],
+      // Plain text (no markdown)
+      ["just plain text", "just plain text", "plain text"],
+      // Empty string
+      ["", "", "empty string"],
+      // Plain text (no markdown)
+      ["just plain text", "just plain text", "plain text"],
+      // Empty string
+      ["", "", "empty string"],
+    ])(
+      "should strip markdown: %s -> %s (%s)",
+      (input: string, expected: string, _description: string) => {
+        expect(Strings.stripMarkdown(input)).toBe(expected);
+      },
+    );
+  });
+
   describe("countChars", () => {
     describe("it should count characters correctly", () => {
       const testCases = [
diff --git a/frontend/src/ts/components/modals/CustomTextModal.tsx b/frontend/src/ts/components/modals/CustomTextModal.tsx
index 602cda856cab..943f840c2dcd 100644
--- a/frontend/src/ts/components/modals/CustomTextModal.tsx
+++ b/frontend/src/ts/components/modals/CustomTextModal.tsx
@@ -324,8 +324,17 @@ export function CustomTextModal(): JSXElement {
     const file = fileInputRef?.files?.[0];
     if (!file) return;
 
-    if (file.type !== "text/plain") {
-      showErrorNotification("File is not a text file", { durationMs: 5000 });
+    const fileExtension = file.name.split(".").pop()?.toLowerCase() ?? "";
+
+    const isTextFile = file.type === "text/plain" || fileExtension === "txt";
+
+    const isMarkdownFile =
+      file.type === "text/markdown" ||
+      file.type === "text/x-markdown" ||
+      fileExtension === "md";
+
+    if (!isMarkdownFile && !isTextFile) {
+      showErrorNotification("Unsupported file type", { durationMs: 5000 });
       return;
     }
 
@@ -333,7 +342,8 @@ export function CustomTextModal(): JSXElement {
     reader.readAsText(file, "UTF-8");
     reader.onload = (e) => {
       const content = e.target?.result as string;
-      form.setFieldValue("text", content);
+      const text = isMarkdownFile ? Strings.stripMarkdown(content) : content;
+      form.setFieldValue("text", text);
       fileInputRef.value = "";
     };
     reader.onerror = () => {
@@ -618,7 +628,7 @@ export function CustomTextModal(): JSXElement {
                 ref={fileInputRef}
                 type="file"
                 class="hidden"
-                accept=".txt"
+                accept=".txt,.md"
                 onChange={handleFileOpen}
               />
               <Button
diff --git a/frontend/src/ts/utils/strings.ts b/frontend/src/ts/utils/strings.ts
index 1dba0722794e..320943bcee7c 100644
--- a/frontend/src/ts/utils/strings.ts
+++ b/frontend/src/ts/utils/strings.ts
@@ -402,6 +402,51 @@ export function replaceUnderscoresWithSpaces(text: string): string {
   return text.replace(/_/g, " ");
 }
 
+/**
+ * Strips all Markdown syntax from a string, returning plain text only.
+ * Handles: code blocks, inline code, images, links, headings, bold/italic,
+ * strikethrough, blockquotes, horizontal rules, list markers, task lists,
+ * tables, and HTML tags.
+ * @param text The Markdown string to strip.
+ * @returns The plain text with all Markdown syntax removed.
+ */
+export function stripMarkdown(text: string): string {
+  // 1. Remove fenced code blocks (with optional language specifier)
+  text = text.replace(/```[\s\S]*?```/g, "");
+  // 2. Remove inline code
+  text = text.replace(/`([^`]+)`/g, "$1");
+  // 3. Remove images (keep alt text)
+  text = text.replace(/!\[([^\]]*)\]\([^)]+\)/g, "$1");
+  // 4. Remove links (keep text)
+  text = text.replace(/\[([^\]]*)\]\([^)]+\)/g, "$1");
+  // 5. Remove strikethrough markers
+  text = text.replace(/~~([^~]+)~~/g, "$1");
+  // 6. Remove heading markers
+  text = text.replace(/^#{1,6}\s+/gm, "");
+  // 7. Remove bold/italic markers (2+ consecutive, not single chars)
+  text = text.replace(/\*{2,}|_{2,}/g, "");
+  // 8. Remove blockquote markers
+  text = text.replace(/^>\s*/gm, "");
+  // 9. Remove horizontal rules
+  text = text.replace(/^[\-*_*]{3,}\s*$/gm, "");
+  // 10. Remove task list markers (bare or prefixed with -*/+)
+  text = text.replace(/^\s*[-*+]\s*\[[ xX]\]\s+/gm, "");
+  text = text.replace(/^\s*\[[ xX]\]\s+/gm, "");
+  // 11. Remove unordered list markers
+  text = text.replace(/^\s*[-*+]\s+/gm, "");
+  // 12. Remove ordered list markers
+  text = text.replace(/^\s*[\d]+\.\s+/gm, "");
+  // 13. Remove table pipe characters
+  text = text.replace(/\|/g, "");
+  // 14. Remove HTML tags
+  text = text.replace(/<[^>]+>/g, "");
+  // 15. Normalize whitespace
+  text = text.replace(/[\r\n]+/g, "\n");
+  text = text.replace(/ +/g, " ");
+  text = text.trim();
+  return text;
+}
+
 export function replaceSpacesWithUnderscores(text: string): string {
   return text.replace(/ /g, "_");
 }