diff --git a/e2e/compareWith.spec.ts b/e2e/compareWith.spec.ts
new file mode 100644
index 00000000..58b15e0e
--- /dev/null
+++ b/e2e/compareWith.spec.ts
@@ -0,0 +1,41 @@
+/**
+ * IDEA's Compare With…: project tree (git and non-git projects alike), the
+ * editor content menu and the editor tab menu. Outside the desktop app the OS
+ * dialog is replaced by a browser file picker and the chosen file is compared
+ * as text.
+ */
+import { expect, openFromTree, test } from "./fixtures";
+
+test("project tree menu offers Compare With… for a file", async ({ workbench: page }) => {
+  await page.getByRole("treeitem", { name: "README.md", exact: true }).click({ button: "right" });
+  // The accessible name carries the shortcut: "Compare With… ⌘D".
+  await expect(page.getByRole("menuitem", { name: /^Compare With…/ })).toBeVisible();
+  await page.keyboard.press("Escape");
+});
+
+test("editor tab menu offers Compare With…", async ({ workbench: page }) => {
+  await openFromTree(page, "README.md");
+  await page
+    .getByRole("tablist", { name: "Editor tabs" })
+    .getByRole("tab", { name: "README.md" })
+    .click({ button: "right" });
+  await expect(page.getByRole("menuitem", { name: /^Compare With…/ })).toBeVisible();
+  await page.keyboard.press("Escape");
+});
+
+test("editor menu offers Compare With…", async ({ workbench: page }) => {
+  const editor = await openFromTree(page, "README.md");
+  await editor.locator(".cm-content").click({ button: "right" });
+  await expect(page.getByRole("menuitem", { name: /^Compare With…/ })).toBeVisible();
+  await expect(page.getByRole("menuitem", { name: "Compare with Clipboard", exact: true })).toBeVisible();
+  await page.keyboard.press("Escape");
+});
+
+test("Compare With… compares against a file picked in the browser", async ({ workbench: page }) => {
+  await page.getByRole("treeitem", { name: "README.md", exact: true }).click({ button: "right" });
+  const chooser = page.waitForEvent("filechooser");
+  await page.getByRole("menuitem", { name: /^Compare With…/ }).click();
+  await (await chooser).setFiles({ name: "other.md", mimeType: "text/markdown", buffer: Buffer.from("other text\n") });
+  const tabs = page.getByRole("tablist", { name: "Editor tabs" });
+  await expect(tabs.getByRole("tab", { name: /other\.md/ })).toBeVisible({ timeout: 15_000 });
+});
diff --git a/src/editor/core/controller.ts b/src/editor/core/controller.ts
index 6c85fcf1..ff1a6859 100644
--- a/src/editor/core/controller.ts
+++ b/src/editor/core/controller.ts
@@ -708,6 +708,12 @@ export class EditorController implements SlotHost {
             localHistoryMenu(slot.model.path),
             gitMenu(slot.model.path),
             { kind: "separator" },
+            {
+              kind: "action",
+              action: "diff.compareWith",
+              arg: slot.model.path,
+              label: "Compare With…",
+            },
             {
               kind: "action",
               action: "diff.compareWithClipboard",
@@ -1598,6 +1604,9 @@ export class EditorController implements SlotHost {
             localHistoryMenu(path),
             ...(inProject ? [gitMenu(path)] : []),
             { kind: "separator" },
+            { kind: "action", action: "diff.compareWith", arg: path, label: "Compare With…" },
+            { kind: "action", action: "diff.compareWithClipboard", arg: { path }, label: "Compare with Clipboard" },
+            { kind: "separator" },
             {
               label: "Copy Path/Reference…",
               submenu: [
diff --git a/src/features/project-tree/contextMenu.test.ts b/src/features/project-tree/contextMenu.test.ts
index daa6e3ba..80cebc34 100644
--- a/src/features/project-tree/contextMenu.test.ts
+++ b/src/features/project-tree/contextMenu.test.ts
@@ -177,6 +177,17 @@ describe("project view context menu", () => {
     expect(l).not.toContain("Compare With…");
   });
 
+  it("offers Compare With… in a non-git project too", () => {
+    useProject.setState({
+      project: { name: "p", root: ROOT, isGit: false, settings: {} } as never,
+      settings: {} as never,
+    });
+    const l = labels(contextMenuItems([node(`${ROOT}/a.py`)]));
+    expect(l).not.toContain("Git");
+    expect(l).toContain("Compare With…");
+    expect(labels(contextMenuItems([node(`${ROOT}/a.py`), node(`${ROOT}/b.py`)]))).toContain("Compare Files");
+  });
+
   it("never shows an empty submenu", () => {
     disposers.forEach((d) => d());
     disposers = [];
diff --git a/src/features/vcs/compare.tsx b/src/features/vcs/compare.tsx
index 8c799284..a2799e61 100644
--- a/src/features/vcs/compare.tsx
+++ b/src/features/vcs/compare.tsx
@@ -92,6 +92,34 @@ async function pickFile(near: string): Promise<string | null> {
   return (Array.isArray(picked) ? picked[0] : picked) ?? null;
 }
 
+/**
+ * The file to compare `path` against: the OS file dialog on the desktop; a
+ * browser file picker's contents elsewhere (remote development / `pnpm dev`),
+ * compared as text since no absolute path is available to the backend.
+ */
+async function pickComparison(
+  path: string,
+): Promise<{ type: "file"; path: string } | { type: "text"; text: string; label: string } | null> {
+  if (isTauri()) {
+    const picked = await pickFile(path);
+    return picked ? { type: "file", path: picked } : null;
+  }
+  if (typeof document === "undefined") {
+    info("Compare With needs the desktop app or a browser file picker");
+    return null;
+  }
+  const chosen = await new Promise<File | null>((resolve) => {
+    const input = document.createElement("input");
+    input.type = "file";
+    input.onchange = () => resolve(input.files?.[0] ?? null);
+    // Chrome fires `cancel` (or focus returns) when the dialog is dismissed.
+    input.addEventListener("cancel", () => resolve(null));
+    input.click();
+  });
+  if (!chosen) return null;
+  return { type: "text", text: await chosen.text(), label: chosen.name };
+}
+
 const contextPath = (arg: unknown) => argPath(arg) ?? maybeEditorService()?.activePath() ?? undefined;
 
 export function registerCompareActions(): () => void {
@@ -186,9 +214,18 @@ export function registerCompareActions(): () => void {
       run: async ({ arg }) => {
         const path = contextPath(arg);
         if (!path) return info("Open or select a file to compare");
-        const other = await pickFile(path);
-        if (!other || other === path) return;
-        await openDiff(compareFilesData(path, other));
+        const other = await pickComparison(path);
+        if (!other) return;
+        if (other.type === "file") {
+          if (other.path === path) return;
+          await openDiff(compareFilesData(path, other.path));
+        } else {
+          await openDiff({
+            path,
+            left: { type: "text", text: other.text, label: other.label },
+            right: { type: "worktree", label: displayPath(path) },
+          });
+        }
       },
     },
     {