diff --git a/README.md b/README.md
index 4d3a113..949e756 100644
--- a/README.md
+++ b/README.md
@@ -385,6 +385,8 @@ The HTML output accepts a Javascript object with configuration. Possible options
   For example: `{ "tag-file-changed": "<span class="d2h-tag d2h-changed d2h-changed-tag">MODIFIED</span>" }`
   > For more information regarding the possible templates look into
   > [src/templates](https://github.com/rtfpessoa/diff2html/tree/master/src/templates)
+- `highlightLanguages`: Map of extension to language name, used for highlighting. This overrides the default language
+  detection based on file extensions.
 
 ### Diff2Html Browser
 
diff --git a/src/ui/js/diff2html-ui-base.ts b/src/ui/js/diff2html-ui-base.ts
index 7aaaa5f..9a84326 100644
--- a/src/ui/js/diff2html-ui-base.ts
+++ b/src/ui/js/diff2html-ui-base.ts
@@ -9,6 +9,7 @@ export interface Diff2HtmlUIConfig extends Diff2HtmlConfig {
   highlight?: boolean;
   fileListToggle?: boolean;
   fileListStartVisible?: boolean;
+  highlightLanguages?: Map<string, string>;
   /**
    * @deprecated since version 3.1.0
    * Smart selection is now enabled by default with vanilla CSS
@@ -23,6 +24,7 @@ export const defaultDiff2HtmlUIConfig = {
   highlight: true,
   fileListToggle: true,
   fileListStartVisible: false,
+  highlightLanguages: new Map<string, string>(),
   /**
    * @deprecated since version 3.1.0
    * Smart selection is now enabled by default with vanilla CSS
@@ -141,8 +143,16 @@ export class Diff2HtmlUI {
     files.forEach(file => {
       // HACK: help Typescript know that `this.hljs` is defined since we already checked it
       if (this.hljs === null) return;
+
       const language = file.getAttribute('data-lang');
-      const hljsLanguage = language ? getLanguage(language) : 'plaintext';
+
+      const hljsLanguage =
+        language && this.config.highlightLanguages.has(language)
+          ? // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+            this.config.highlightLanguages.get(language)!
+          : language
+          ? getLanguage(language)
+          : 'plaintext';
 
       // Collect all the code lines and execute the highlight on them
       const codeLines = file.querySelectorAll('.d2h-code-line-ctn');
diff --git a/website/templates/pages/demo/demo.ts b/website/templates/pages/demo/demo.ts
index 0cca1f5..53c7019 100644
--- a/website/templates/pages/demo/demo.ts
+++ b/website/templates/pages/demo/demo.ts
@@ -22,7 +22,7 @@ import './demo.css';
 type URLParams = {
   diff?: string;
   diffTooBigMessage?: string;
-  [key: string]: string | boolean | number | undefined;
+  [key: string]: string | boolean | number | Map<string, string> | undefined;
 };
 
 const searchParam = 'diff';