diff --git a/gen-go-code.py b/gen-go-code.py
index 85b1f9306..62cb8f4d1 100755
--- a/gen-go-code.py
+++ b/gen-go-code.py
@@ -20,13 +20,13 @@ from kitty.cli import (
     parse_option_spec,
     serialize_as_go_string,
 )
+from kitty.guess_mime_type import text_mimes
 from kitty.key_encoding import config_mod_map
 from kitty.key_names import character_key_name_aliases, functional_key_name_aliases
 from kitty.options.types import Options
 from kitty.rc.base import RemoteCommand, all_command_names, command_for_name
 from kitty.remote_control import global_options_spec
 from kitty.rgb import color_names
-from kitty.guess_mime_type import text_mimes
 
 changed: List[str] = []
 
diff --git a/tools/utils/mimetypes.go b/tools/utils/mimetypes.go
index a5e7db410..a9755a72f 100644
--- a/tools/utils/mimetypes.go
+++ b/tools/utils/mimetypes.go
@@ -3,17 +3,62 @@
 package utils
 
 import (
+	"bufio"
+	"errors"
 	"fmt"
 	"mime"
+	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 )
 
 var _ = fmt.Print
+var user_mime_only_once sync.Once
+var user_defined_mime_map map[string]string
+
+func load_mime_file(filename string, mime_map map[string]string) error {
+	f, err := os.Open(filename)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		fields := strings.Fields(scanner.Text())
+		if len(fields) <= 1 || fields[0][0] == '#' {
+			continue
+		}
+		mime_type := fields[0]
+		for _, ext := range fields[1:] {
+			if ext[0] == '#' {
+				break
+			}
+			mime_map["."+ext] = mime_type
+		}
+	}
+	if err := scanner.Err(); err != nil {
+		return err
+	}
+	return nil
+}
+
+func load_user_mime_maps() {
+	conf_path := filepath.Join(ConfigDir(), "mime.types")
+	err := load_mime_file(conf_path, user_defined_mime_map)
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
+		fmt.Fprintln(os.Stderr, "Failed to parse", conf_path, "for MIME types with error:", err)
+	}
+}
 
 func GuessMimeType(filename string) string {
+	user_mime_only_once.Do(load_user_mime_maps)
 	ext := filepath.Ext(filename)
-	mime_with_parameters := mime.TypeByExtension(ext)
+	mime_with_parameters := user_defined_mime_map[ext]
+	if mime_with_parameters == "" {
+		mime_with_parameters = mime.TypeByExtension(ext)
+	}
 	if mime_with_parameters == "" {
 		only_once.Do(set_builtins)
 		mime_with_parameters = builtin_types_map[ext]