diff --git a/deno.jsonc b/deno.jsonc
index d2722df..a028b40 100644
--- a/deno.jsonc
+++ b/deno.jsonc
@@ -19,6 +19,7 @@
     "@fresh/plugin-vite": "jsr:@fresh/plugin-vite@^1.1.2",
     "@hey-api/openapi-ts": "npm:@hey-api/openapi-ts@^0.97.0",
     "@hey-api/vite-plugin": "npm:@hey-api/vite-plugin@^0.3.1",
+    "@imagemagick/magick-wasm": "npm:@imagemagick/magick-wasm@^0.0.40",
     "@kysely/kysely": "jsr:@kysely/kysely@^0.28.16",
     "@preact/signals": "npm:@preact/signals@^2.9.0",
     "@std/encoding": "jsr:@std/encoding@^1.0.10",
diff --git a/deno.lock b/deno.lock
index 5d5b173..fee11a0 100644
--- a/deno.lock
+++ b/deno.lock
@@ -47,6 +47,7 @@
     "npm:@badgateway/oauth2-client@^3.3.1": "3.3.1",
     "npm:@hey-api/openapi-ts@0.97": "0.97.0_typescript@6.0.3",
     "npm:@hey-api/vite-plugin@~0.3.1": "0.3.1_@hey-api+openapi-ts@0.97.0__typescript@6.0.3_vite@7.3.2__@types+node@25.6.0_typescript@6.0.3",
+    "npm:@imagemagick/magick-wasm@^0.0.40": "0.0.40",
     "npm:@opentelemetry/api@^1.9.0": "1.9.1",
     "npm:@preact/signals@^2.5.1": "2.9.0_preact@10.29.1",
     "npm:@preact/signals@^2.9.0": "2.9.0_preact@10.29.1",
@@ -915,6 +916,9 @@
         "vite"
       ]
     },
+    "@imagemagick/magick-wasm@0.0.40": {
+      "integrity": "sha512-vwV4qZ5JfPblYoJTBKn/dAMElXMmIf4inEsCtjskZwU3609ejpz1pvXWE3UEt8G+0L2SYHdoBNKCPU4ezpDXaQ=="
+    },
     "@jridgewell/gen-mapping@0.3.13": {
       "integrity": "sha512-2kkt/7niJ6MgEPxF0bYdQ6etZaA+fQvDcLKckhy1yIQOzaoKjBBjSj63/aLVjYE3qhRt5dvM+uUyfCg6UKCBbA==",
       "dependencies": [
@@ -1759,6 +1763,7 @@
       "npm:@badgateway/oauth2-client@^3.3.1",
       "npm:@hey-api/openapi-ts@0.97",
       "npm:@hey-api/vite-plugin@~0.3.1",
+      "npm:@imagemagick/magick-wasm@^0.0.40",
       "npm:@preact/signals@^2.9.0",
       "npm:@subframe7536/iconv-lite@~0.8.1",
       "npm:jose@^6.2.3",
diff --git a/lib/image.ts b/lib/image.ts
index d5a8b17..c432a91 100644
--- a/lib/image.ts
+++ b/lib/image.ts
@@ -2,9 +2,18 @@
 import type { AppBskyEmbedImages } from "@atcute/bluesky"
 import { type Did } from "@atcute/lexicons"
 import { isLegacyBlob } from "@atcute/lexicons/interfaces"
+import {
+  ImageMagick,
+  initializeImageMagick,
+  MagickFormat,
+} from "@imagemagick/magick-wasm"
+// @ts-ignore: Handled by custom Vite plugin
+import wasmBytes from "@imagemagick/magick-wasm/magick.wasm"
 import { postFile } from "../traq/index.ts"
 import { client } from "./blueskyClient.ts"
 
+const TRAQ_IMAGE_MAX_PIXELS = 2560 * 1600
+
 interface UploadImageParams {
   accessToken: string
   did: Did
@@ -44,7 +53,7 @@ export const uploadImages = async (
         },
         body: {
           channelId: targetChannelId,
-          file: downloadRes,
+          file: await resizeImage(downloadRes),
         },
       })
 
@@ -58,3 +67,35 @@ export const uploadImages = async (
 
   return imageIds
 }
+
+const isUint8ArrayOfArrayBuffer = (
+  data: Uint8Array,
+): data is Uint8Array<ArrayBuffer> => data.buffer instanceof ArrayBuffer
+
+const initMagickPromise = initializeImageMagick(wasmBytes)
+
+const resizeImage = async (imageBlob: Blob) => {
+  await initMagickPromise
+
+  const bytes = ImageMagick.read(await imageBlob.bytes(), (image) => {
+    const imagePixels = image.height * image.width
+
+    if (imagePixels > TRAQ_IMAGE_MAX_PIXELS) {
+      const scale = Math.sqrt(TRAQ_IMAGE_MAX_PIXELS / imagePixels)
+      const newHeight = Math.max(1, Math.floor(image.height * scale))
+      const newWidth = Math.max(1, Math.floor(image.width * scale))
+
+      image.resize(newWidth, newHeight)
+    }
+
+    return image.write(MagickFormat.WebP, (data) => {
+      if (isUint8ArrayOfArrayBuffer(data)) {
+        return data
+      }
+
+      throw new Error("Unexpected data type from ImageMagick")
+    })
+  })
+
+  return new Blob([bytes], { type: "image/webp" })
+}
diff --git a/vite.config.ts b/vite.config.ts
index 9ff3139..8181dec 100644
--- a/vite.config.ts
+++ b/vite.config.ts
@@ -1,6 +1,50 @@
 import { fresh } from "@fresh/plugin-vite"
 import { heyApiPlugin } from "@hey-api/vite-plugin"
-import { defineConfig } from "vite"
+import { defineConfig, type Plugin } from "vite"
+
+const WASM_ID_PREFIX = "\0wasm:"
+
+/**
+ * Vite plugin to load WASM files as Uint8Array
+ *
+ * Deno supports loading WASM files directly, but Vite doesn't.
+ * And using params like `?url` or `?raw` doesn't work for external packages,
+ * so we need to handle `.wasm` files manually.
+ */
+const wasmPlugin = (): Plugin => {
+  return {
+    name: "wasm-loader",
+    enforce: "pre",
+    async resolveId(id, importer, options) {
+      if (!id.endsWith(".wasm")) {
+        return null
+      }
+
+      const resolved = await this.resolve(id, importer, {
+        ...options,
+        skipSelf: true,
+      })
+
+      if (!resolved) {
+        return null
+      }
+
+      return WASM_ID_PREFIX + resolved.id
+    },
+    load: async (id) => {
+      if (!id.startsWith(WASM_ID_PREFIX)) {
+        return null
+      }
+
+      const path = id.slice(WASM_ID_PREFIX.length)
+      const bytes = await Deno.readFile(path)
+
+      return `export default new Uint8Array(${
+        JSON.stringify(Array.from(bytes))
+      })`
+    },
+  }
+}
 
 export default defineConfig({
   resolve: {
@@ -9,6 +53,7 @@ export default defineConfig({
     },
   },
   plugins: [
+    wasmPlugin(), // Must be loaded first to handle WASM imports correctly
     fresh(),
     heyApiPlugin(
       {