diff --git a/apps/web/components/share-modal.tsx b/apps/web/components/share-modal.tsx
index 091a9446..f17ee4c7 100644
--- a/apps/web/components/share-modal.tsx
+++ b/apps/web/components/share-modal.tsx
@@ -18,6 +18,12 @@ import { useLocalStorageUsername } from "@hooks/use-local-storage-username"
 import { useHasCompanyBrain } from "@/hooks/use-company-brain"
 import { toast } from "sonner"
 import * as htmlToImage from "html-to-image"
+import {
+	getShareAspectPreset,
+	SHARE_ASPECT_PRESETS,
+	type ShareAspect,
+	shareAspectMaxHeightDvh,
+} from "@/lib/share-aspect"
 
 type BackgroundTheme = "gradient" | "dark-gradient" | "black"
 
@@ -281,9 +287,11 @@ export function ShareModal({
 	const isCompanyBrain = useHasCompanyBrain()
 	const [selectedTheme, setSelectedTheme] =
 		useState<BackgroundTheme>("gradient")
+	const [selectedAspect, setSelectedAspect] = useState<ShareAspect>("post")
 	const [isCopying, setIsCopying] = useState(false)
 	const [copied, setCopied] = useState(false)
 	const previewRef = useRef<HTMLDivElement>(null)
+	const aspectPreset = getShareAspectPreset(selectedAspect)
 
 	const localStorageUsername = useLocalStorageUsername()
 	const displayName =
@@ -438,8 +446,10 @@ export function ShareModal({
 					{/* Preview area */}
 					<div
 						ref={previewRef}
-						className="relative w-full aspect-[674/505] max-h-[48dvh] rounded-[14px] overflow-hidden"
+						className="relative mx-auto w-full rounded-[14px] overflow-hidden"
 						style={{
+							aspectRatio: aspectPreset.ratio,
+							maxHeight: `${shareAspectMaxHeightDvh(selectedAspect)}dvh`,
 							boxShadow: "inset 2.42px 2.42px 4.26316px rgba(11, 15, 21, 0.7)",
 						}}
 					>
@@ -493,6 +503,26 @@ export function ShareModal({
 								isSelected={selectedTheme === "black"}
 								onClick={() => setSelectedTheme("black")}
 							/>
+							<div className="mx-1 h-5 w-px bg-white/10" aria-hidden />
+							<div className="flex items-center gap-1 rounded-full bg-[#0D121A] p-0.5">
+								{SHARE_ASPECT_PRESETS.map((preset) => (
+									<button
+										key={preset.id}
+										type="button"
+										aria-pressed={selectedAspect === preset.id}
+										onClick={() => setSelectedAspect(preset.id)}
+										className={cn(
+											dmSansClassName(),
+											"h-6 rounded-full px-2.5 text-[11px] font-medium transition-colors",
+											selectedAspect === preset.id
+												? "bg-white/[0.12] text-white"
+												: "text-[#8B929E] hover:text-white",
+										)}
+									>
+										{preset.label}
+									</button>
+								))}
+							</div>
 						</div>
 
 						{/* Action buttons */}
diff --git a/apps/web/lib/share-aspect.test.ts b/apps/web/lib/share-aspect.test.ts
new file mode 100644
index 00000000..548934be
--- /dev/null
+++ b/apps/web/lib/share-aspect.test.ts
@@ -0,0 +1,39 @@
+import { describe, expect, it } from "bun:test"
+import {
+	getShareAspectPreset,
+	SHARE_ASPECT_PRESETS,
+	shareAspectMaxHeightDvh,
+	type ShareAspect,
+} from "./share-aspect"
+
+describe("share-aspect presets", () => {
+	it("exposes post, square and story", () => {
+		expect(SHARE_ASPECT_PRESETS.map((p) => p.id)).toEqual([
+			"post",
+			"square",
+			"story",
+		])
+	})
+
+	it("resolves each preset by id", () => {
+		for (const preset of SHARE_ASPECT_PRESETS) {
+			expect(getShareAspectPreset(preset.id)).toBe(preset)
+		}
+	})
+
+	it("falls back to post for an unknown aspect", () => {
+		expect(getShareAspectPreset("nope" as ShareAspect).id).toBe("post")
+	})
+
+	it("has coherent ratio strings and numeric values", () => {
+		expect(getShareAspectPreset("square").value).toBe(1)
+		expect(getShareAspectPreset("post").value).toBeGreaterThan(1) // landscape
+		expect(getShareAspectPreset("story").value).toBeLessThan(1) // portrait
+	})
+
+	it("lets the narrow portrait story use more vertical space than the wide post", () => {
+		expect(shareAspectMaxHeightDvh("story")).toBeGreaterThan(
+			shareAspectMaxHeightDvh("post"),
+		)
+	})
+})
diff --git a/apps/web/lib/share-aspect.ts b/apps/web/lib/share-aspect.ts
new file mode 100644
index 00000000..9e231f4e
--- /dev/null
+++ b/apps/web/lib/share-aspect.ts
@@ -0,0 +1,40 @@
+/**
+ * Aspect-ratio presets for the graph share card, sized for where people post
+ * screenshots. Pure so the mapping can be unit tested.
+ */
+
+export type ShareAspect = "post" | "square" | "story"
+
+export interface ShareAspectPreset {
+	id: ShareAspect
+	label: string
+	/** CSS `aspect-ratio` value (width / height). */
+	ratio: string
+	/** Width / height as a number, for any numeric layout math. */
+	value: number
+}
+
+const POST_PRESET: ShareAspectPreset = {
+	id: "post",
+	label: "Post",
+	ratio: "674 / 505",
+	value: 674 / 505,
+}
+
+export const SHARE_ASPECT_PRESETS: readonly ShareAspectPreset[] = [
+	POST_PRESET,
+	{ id: "square", label: "Square", ratio: "1 / 1", value: 1 },
+	{ id: "story", label: "Story", ratio: "9 / 16", value: 9 / 16 },
+]
+
+export function getShareAspectPreset(aspect: ShareAspect): ShareAspectPreset {
+	return SHARE_ASPECT_PRESETS.find((p) => p.id === aspect) ?? POST_PRESET
+}
+
+/**
+ * A max-height (in dvh) that keeps the preview inside the dialog. Tall (story)
+ * ratios need to be shorter than wide ones so they don't overflow.
+ */
+export function shareAspectMaxHeightDvh(aspect: ShareAspect): number {
+	return aspect === "story" ? 60 : 48
+}