diff --git a/adapters/discord/src/message.ts b/adapters/discord/src/message.ts
index 9ec1b2e0..8ea0c763 100644
--- a/adapters/discord/src/message.ts
+++ b/adapters/discord/src/message.ts
@@ -110,30 +110,34 @@ export class DiscordMessageEncoder extends MessageEncoder<DiscordBot> {
       return this.post({ ...addition, content: attrs.url })
     }
 
-    const sendDownload = () => this.sendEmbed(attrs, addition)
-
-    if (['file:', 'data:', 'base64:'].some((prefix) => attrs.url.startsWith(prefix))) {
-      return await sendDownload()
+    if (this.bot.http.isPrivate(attrs.url)) {
+      return await this.sendEmbed(attrs, addition)
     }
 
     const mode = attrs.mode as DiscordMessageEncoder.HandleExternalAsset || handleExternalAsset
     if (mode === 'download' || handleMixedContent === 'attach' && addition.content || type === 'file') {
-      return sendDownload()
+      return this.sendEmbed(attrs, addition)
     } else if (mode === 'direct') {
       return sendDirect()
     }
 
     // auto mode
-    return await this.bot.ctx.http.head(attrs.url, {
+    if (await this.checkMediaType(attrs.url, type)) {
+      return sendDirect()
+    } else {
+      return this.sendEmbed(attrs, addition)
+    }
+  }
+
+  checkMediaType(url: string, type: string) {
+    if (url.startsWith('https://cdn.discordapp.com/')) return true
+    return this.bot.ctx.http.head(url, {
       headers: { accept: type + '/*' },
-      timeout: +attrs.timeout || undefined,
-    }).then((headers) => {
-      if (headers['content-type'].startsWith(type)) {
-        return sendDirect()
-      } else {
-        return sendDownload()
-      }
-    }, sendDownload)
+      timeout: 1000,
+    }).then(
+      (headers) => headers['content-type'].startsWith(type),
+      () => false,
+    )
   }
 
   async ensureWebhook() {
diff --git a/adapters/kook/src/message.ts b/adapters/kook/src/message.ts
index fbf005c2..ae773921 100644
--- a/adapters/kook/src/message.ts
+++ b/adapters/kook/src/message.ts
@@ -41,7 +41,7 @@ export class KookMessageEncoder extends MessageEncoder<KookBot> {
   }
 
   private async transformUrl({ type, attrs }: h) {
-    if (['file:', 'base64:', 'data:'].some(protocol => attrs.url.startsWith(protocol))) {
+    if (this.bot.http.isPrivate(attrs.url)) {
       const payload = new FormData()
       const result = await this.bot.ctx.http.file(attrs.url, attrs)
       payload.append('file', Buffer.from(result.data), {
diff --git a/packages/axios/src/index.ts b/packages/axios/src/index.ts
index 50c78522..2956b84d 100644
--- a/packages/axios/src/index.ts
+++ b/packages/axios/src/index.ts
@@ -42,7 +42,7 @@ function addressToNumber(address: string) {
 }
 
 function isPrivate(hostname: string) {
-  if (/^(\d+)\.(\d+)\.(\d+)\.(\d+)$/.test(hostname)) return false
+  if (!/^(\d+)\.(\d+)\.(\d+)\.(\d+)$/.test(hostname)) return false
   for (const cidr of ranges) {
     const [address, length] = cidr.split('/')
     const mask = -1n << BigInt(32 - +length)
@@ -147,9 +147,14 @@ export class Quester {
     return { mime, filename: name, data }
   }
 
-  async url(url: string) {
-    const { hostname } = new URL(url)
-    if (!isPrivate(hostname)) return url
+  isPrivate(url: string) {
+    const { hostname, protocol } = new URL(url)
+    if (protocol !== 'http:' && protocol !== 'https:') return true
+    return isPrivate(hostname)
+  }
+
+  async toPublic(url: string) {
+    if (!this.isPrivate(url)) return url
     const { headers, data } = await this.axios(url, {
       method: 'GET',
       responseType: 'arraybuffer',