diff --git a/websh_front/src/index.nim b/websh_front/src/index.nim
index adf899e..e08a164 100644
--- a/websh_front/src/index.nim
+++ b/websh_front/src/index.nim
@@ -18,6 +18,7 @@ type
   ImageObj = object
     image: cstring
     filesize: cint
+    format: cstring
   MediaObj = object
     name, data: cstring
 
@@ -248,7 +249,11 @@ proc createDom(): VNode =
                 for img in outputImages:
                   tdiv:
                     # imgでbase64を表示するときに必要なメタ情報を追加
-                    img(src = "data:image/png;base64," & img.image)
+                    case $img.format
+                    of "gif":
+                      img(src = "data:image/gif;base64," & img.image)
+                    else:
+                      img(src = "data:image/png;base64," & img.image)
                   tdiv:
                     text &"{img.filesize} byte"
 
diff --git a/websh_server/src/websh_server.nim b/websh_server/src/websh_server.nim
index 1487fbb..7b61c8f 100644
--- a/websh_server/src/websh_server.nim
+++ b/websh_server/src/websh_server.nim
@@ -14,6 +14,7 @@ type
   ImageObj* = object
     image*: string
     filesize*: int
+    format*: string
 
 const
   scriptName = "exec.sh"
@@ -29,7 +30,13 @@ proc getImages(dir: string): seq[ImageObj] =
     if not path.existsFile:
       continue
     let content = readFile(path)
-    let img = ImageObj(image: base64.encode(content), filesize: content.len)
+    var format = "png"
+    if 6 < content.len:
+      let f = content[0..<6]
+      case f
+      of "GIF89a": format = "gif"
+      else: discard
+    let img = ImageObj(image: base64.encode(content), filesize: content.len, format: format)
     result.add(img)
 
 proc createMediaFiles(dir: string, medias: seq[string]) =