diff --git a/src/app/components/text-viewer/TextViewer.tsx b/src/app/components/text-viewer/TextViewer.tsx
index 37642db..7829fb3 100644
--- a/src/app/components/text-viewer/TextViewer.tsx
+++ b/src/app/components/text-viewer/TextViewer.tsx
@@ -4,7 +4,6 @@ import classNames from 'classnames';
 import { Box, Chip, Header, Icon, IconButton, Icons, Scroll, Text, as } from 'folds';
 import { ErrorBoundary } from 'react-error-boundary';
 import * as css from './TextViewer.css';
-import { mimeTypeToExt } from '../../utils/mimeTypes';
 import { copyToClipboard } from '../../utils/dom';
 
 const ReactPrism = lazy(() => import('../../plugins/react-prism/ReactPrism'));
@@ -12,12 +11,12 @@ const ReactPrism = lazy(() => import('../../plugins/react-prism/ReactPrism'));
 export type TextViewerProps = {
   name: string;
   text: string;
-  mimeType: string;
+  langName: string;
   requestClose: () => void;
 };
 
 export const TextViewer = as<'div', TextViewerProps>(
-  ({ className, name, text, mimeType, requestClose, ...props }, ref) => {
+  ({ className, name, text, langName, requestClose, ...props }, ref) => {
     const handleCopy = () => {
       copyToClipboard(text);
     };
@@ -51,10 +50,7 @@ export const TextViewer = as<'div', TextViewerProps>(
           alignItems="Center"
         >
           <Scroll hideTrack variant="Background" visibility="Hover">
-            <Text
-              as="pre"
-              className={classNames(css.TextViewerPre, `language-${mimeTypeToExt(mimeType)}`)}
-            >
+            <Text as="pre" className={classNames(css.TextViewerPre, `language-${langName}`)}>
               <ErrorBoundary fallback={<code>{text}</code>}>
                 <Suspense fallback={<code>{text}</code>}>
                   <ReactPrism>{(codeRef) => <code ref={codeRef}>{text}</code>}</ReactPrism>
diff --git a/src/app/organisms/room/message/FileContent.tsx b/src/app/organisms/room/message/FileContent.tsx
index 303c453..9c65966 100644
--- a/src/app/organisms/room/message/FileContent.tsx
+++ b/src/app/organisms/room/message/FileContent.tsx
@@ -23,7 +23,12 @@ import { useMatrixClient } from '../../../hooks/useMatrixClient';
 import { getFileSrcUrl, getSrcFile } from './util';
 import { bytesToSize } from '../../../utils/common';
 import { TextViewer } from '../../../components/text-viewer';
-import { READABLE_TEXT_MIME_TYPES } from '../../../utils/mimeTypes';
+import {
+  READABLE_EXT_TO_MIME_TYPE,
+  READABLE_TEXT_MIME_TYPES,
+  getFileNameExt,
+  mimeTypeToExt,
+} from '../../../utils/mimeTypes';
 import { PdfViewer } from '../../../components/Pdf-viewer';
 import * as css from './styles.css';
 
@@ -103,7 +108,11 @@ function ReadTextFile({ body, mimeType, url, encInfo }: Omit<FileContentProps, '
                 <TextViewer
                   name={body}
                   text={textState.data}
-                  mimeType={mimeType}
+                  langName={
+                    READABLE_TEXT_MIME_TYPES.includes(mimeType)
+                      ? mimeTypeToExt(mimeType)
+                      : mimeTypeToExt(READABLE_EXT_TO_MIME_TYPE[getFileNameExt(body)] ?? mimeType)
+                  }
                   requestClose={() => setTextViewer(false)}
                 />
               </Modal>
@@ -247,7 +256,8 @@ function DownloadFile({ body, mimeType, url, info, encInfo }: FileContentProps)
 export const FileContent = as<'div', FileContentProps>(
   ({ body, mimeType, url, info, encInfo, ...props }, ref) => (
     <Box direction="Column" gap="300" {...props} ref={ref}>
-      {READABLE_TEXT_MIME_TYPES.includes(mimeType) && (
+      {(READABLE_TEXT_MIME_TYPES.includes(mimeType) ||
+        READABLE_EXT_TO_MIME_TYPE[getFileNameExt(body)]) && (
         <ReadTextFile body={body} mimeType={mimeType} url={url} encInfo={encInfo} />
       )}
       {mimeType === 'application/pdf' && (
diff --git a/src/app/organisms/room/message/Message.tsx b/src/app/organisms/room/message/Message.tsx
index 8f25861..13e4326 100644
--- a/src/app/organisms/room/message/Message.tsx
+++ b/src/app/organisms/room/message/Message.tsx
@@ -246,7 +246,7 @@ export const MessageSourceCodeItem = as<
             <Modal variant="Surface" size="500">
               <TextViewer
                 name="Source Code"
-                mimeType="application/json"
+                langName="json"
                 text={text}
                 requestClose={handleClose}
               />
diff --git a/src/app/utils/mimeTypes.ts b/src/app/utils/mimeTypes.ts
index c883ddb..2a92367 100644
--- a/src/app/utils/mimeTypes.ts
+++ b/src/app/utils/mimeTypes.ts
@@ -57,6 +57,43 @@ export const READABLE_TEXT_MIME_TYPES = [
   ...TEXT_MIME_TYPE,
 ];
 
+export const READABLE_EXT_TO_MIME_TYPE: Record<string, string> = {
+  go: 'text/go',
+  rs: 'text/rust',
+  py: 'text/python',
+  swift: 'text/swift',
+  c: 'text/c',
+  cpp: 'text/cpp',
+  java: 'text/java',
+  kt: 'text/kotlin',
+  lua: 'text/lua',
+  php: 'text/php',
+  ts: 'text/typescript',
+  js: 'text/javascript',
+  jsx: 'text/jsx',
+  tsx: 'text/tsx',
+  html: 'text/html',
+  xhtml: 'text/xhtml',
+  xht: 'text/xhtml',
+  css: 'text/css',
+  scss: 'text/scss',
+  sass: 'text/sass',
+  json: 'text/json',
+  md: 'text/markdown',
+  yaml: 'text/yaml',
+  yni: 'text/yni',
+  xml: 'text/xml',
+  txt: 'text/plain',
+  text: 'text/plain',
+  conf: 'text/conf',
+  cfg: 'text/conf',
+  cnf: 'text/conf',
+  log: 'text/log',
+  me: 'text/me',
+  cvs: 'text/cvs',
+  tvs: 'text/tvs',
+};
+
 export const ALLOWED_BLOB_MIME_TYPES = [
   ...IMAGE_MIME_TYPES,
   ...VIDEO_MIME_TYPES,
@@ -92,3 +129,7 @@ export const mimeTypeToExt = (mimeType: string): string => {
   const extStart = mimeType.lastIndexOf('/') + 1;
   return mimeType.slice(extStart);
 };
+export const getFileNameExt = (fileName: string): string => {
+  const extStart = fileName.lastIndexOf('.') + 1;
+  return fileName.slice(extStart);
+};