diff --git a/app/assets/javascripts/discourse/lib/utilities.js.es6 b/app/assets/javascripts/discourse/lib/utilities.js.es6
index e71223f337..3ce16c30dd 100644
--- a/app/assets/javascripts/discourse/lib/utilities.js.es6
+++ b/app/assets/javascripts/discourse/lib/utilities.js.es6
@@ -282,7 +282,7 @@ export function validateUploadedFile(file, opts) {
   return true;
 }
 
-const IMAGES_EXTENSIONS_REGEX = /(png|jpe?g|gif|bmp|tiff?|svg|webp|ico)/i;
+const IMAGES_EXTENSIONS_REGEX = /(png|jpe?g|gif|svg|ico)/i;
 
 function extensionsToArray(exts) {
   return exts
@@ -348,7 +348,7 @@ export function authorizedExtensions() {
 
 export function authorizedImagesExtensions() {
   return authorizesAllExtensions()
-    ? "png, jpg, jpeg, gif, bmp, tiff, svg, webp, ico"
+    ? "png, jpg, jpeg, gif, svg, ico"
     : imagesExtensions().join(", ");
 }
 
@@ -376,7 +376,7 @@ export function authorizesOneOrMoreImageExtensions() {
 }
 
 export function isAnImage(path) {
-  return /\.(png|jpe?g|gif|bmp|tiff?|svg|webp|ico)$/i.test(path);
+  return /\.(png|jpe?g|gif|svg|ico)$/i.test(path);
 }
 
 function uploadTypeFromFileName(fileName) {
diff --git a/app/models/optimized_image.rb b/app/models/optimized_image.rb
index 8da1f8753d..fbcc5621d0 100644
--- a/app/models/optimized_image.rb
+++ b/app/models/optimized_image.rb
@@ -29,7 +29,6 @@ class OptimizedImage < ActiveRecord::Base
   end
 
   def self.create_for(upload, width, height, opts = {})
-
     return unless width > 0 && height > 0
     return if upload.try(:sha1).blank?
 
@@ -180,7 +179,7 @@ class OptimizedImage < ActiveRecord::Base
     end
   end
 
-  IM_DECODERS ||= /\A(jpe?g|png|tiff?|bmp|ico|gif)\z/i
+  IM_DECODERS ||= /\A(jpe?g|png|ico|gif)\z/i
 
   def self.prepend_decoder!(path, ext_path = nil, opts = nil)
     opts ||= {}
diff --git a/lib/upload_creator.rb b/lib/upload_creator.rb
index 0aa4af84b1..521b405d55 100644
--- a/lib/upload_creator.rb
+++ b/lib/upload_creator.rb
@@ -3,8 +3,6 @@ require_dependency "image_sizer"
 
 class UploadCreator
 
-  TYPES_CONVERTED_TO_JPEG ||= %i{bmp png}
-
   TYPES_TO_CROP ||= %w{avatar card_background custom_emoji profile_background}.each(&:freeze)
 
   WHITELISTED_SVG_ELEMENTS ||= %w{
@@ -47,7 +45,7 @@ class UploadCreator
         if @image_info.type.to_s == "svg"
           whitelist_svg!
         elsif !Rails.env.test? || @opts[:force_optimize]
-          convert_to_jpeg! if should_convert_to_jpeg?
+          convert_to_jpeg! if convert_png_to_jpeg?
           downsize!        if should_downsize?
 
           return @upload   if is_still_too_big?
@@ -158,8 +156,8 @@ class UploadCreator
 
   MIN_PIXELS_TO_CONVERT_TO_JPEG ||= 1280 * 720
 
-  def should_convert_to_jpeg?
-    return false if !TYPES_CONVERTED_TO_JPEG.include?(@image_info.type)
+  def convert_png_to_jpeg?
+    return false unless @image_info.type == :png
     return true  if @opts[:pasted]
     return false if SiteSetting.png_to_jpg_quality == 100
     pixels > MIN_PIXELS_TO_CONVERT_TO_JPEG
diff --git a/script/downsize_uploads.rb b/script/downsize_uploads.rb
index fae1ab4374..e04266e3f0 100644
--- a/script/downsize_uploads.rb
+++ b/script/downsize_uploads.rb
@@ -7,7 +7,7 @@ puts '', "Downsizing uploads size to no more than #{max_image_pixels} pixels"
 
 count = 0
 
-Upload.where("lower(extension) in (?)", ['jpg', 'jpeg', 'gif', 'png', 'bmp', 'tif', 'tiff']).find_each do |upload|
+Upload.where("lower(extension) in (?)", ['jpg', 'jpeg', 'gif', 'png']).find_each do |upload|
   count += 1
   print "\r%8d".freeze % count
   absolute_path = Discourse.store.path_for(upload)
diff --git a/spec/models/optimized_image_spec.rb b/spec/models/optimized_image_spec.rb
index 4c832a8f4b..4a52540161 100644
--- a/spec/models/optimized_image_spec.rb
+++ b/spec/models/optimized_image_spec.rb
@@ -155,8 +155,8 @@ describe OptimizedImage do
   describe ".safe_path?" do
 
     it "correctly detects unsafe paths" do
-      expect(OptimizedImage.safe_path?("/path/A-AA/22_00.TIFF")).to eq(true)
-      expect(OptimizedImage.safe_path?("/path/AAA/2200.TIFF")).to eq(true)
+      expect(OptimizedImage.safe_path?("/path/A-AA/22_00.JPG")).to eq(true)
+      expect(OptimizedImage.safe_path?("/path/AAA/2200.JPG")).to eq(true)
       expect(OptimizedImage.safe_path?("/tmp/a.png")).to eq(true)
       expect(OptimizedImage.safe_path?("../a.png")).to eq(false)
       expect(OptimizedImage.safe_path?("/tmp/a.png\\test")).to eq(false)
diff --git a/test/javascripts/lib/utilities-test.js.es6 b/test/javascripts/lib/utilities-test.js.es6
index d5280741a5..f19ea0e804 100644
--- a/test/javascripts/lib/utilities-test.js.es6
+++ b/test/javascripts/lib/utilities-test.js.es6
@@ -204,16 +204,14 @@ QUnit.test("replaces GUID in image alt text on iOS", assert => {
 });
 
 QUnit.test("isAnImage", assert => {
-  ["png", "jpg", "jpeg", "bmp", "gif", "tif", "tiff", "ico"].forEach(
-    extension => {
-      var image = "image." + extension;
-      assert.ok(isAnImage(image), image + " is recognized as an image");
-      assert.ok(
-        isAnImage("http://foo.bar/path/to/" + image),
-        image + " is recognized as an image"
-      );
-    }
-  );
+  ["png", "jpg", "jpeg", "gif", "ico"].forEach(extension => {
+    var image = "image." + extension;
+    assert.ok(isAnImage(image), image + " is recognized as an image");
+    assert.ok(
+      isAnImage("http://foo.bar/path/to/" + image),
+      image + " is recognized as an image"
+    );
+  });
   assert.not(isAnImage("file.txt"));
   assert.not(isAnImage("http://foo.bar/path/to/file.txt"));
   assert.not(isAnImage(""));