diff --git a/apps/builder/components/board/graph/BlockNode/StepNode/SettingsPopoverContent/bodies/WebhookSettings/WebhookSettings.tsx b/apps/builder/components/board/graph/BlockNode/StepNode/SettingsPopoverContent/bodies/WebhookSettings/WebhookSettings.tsx
index 1e48f46731..506bddd6b5 100644
--- a/apps/builder/components/board/graph/BlockNode/StepNode/SettingsPopoverContent/bodies/WebhookSettings/WebhookSettings.tsx
+++ b/apps/builder/components/board/graph/BlockNode/StepNode/SettingsPopoverContent/bodies/WebhookSettings/WebhookSettings.tsx
@@ -159,6 +159,7 @@ export const WebhookSettings = ({
           <AccordionPanel pb={4} as={Stack} spacing="6">
             <CodeEditor
               value={webhook?.body ?? ''}
+              lang="json"
               onChange={handleBodyChange}
             />
           </AccordionPanel>
@@ -181,7 +182,9 @@ export const WebhookSettings = ({
       <Button onClick={handleTestRequestClick} colorScheme="blue">
         Test the request
       </Button>
-      {testResponse && <CodeEditor isReadOnly value={testResponse} />}
+      {testResponse && (
+        <CodeEditor isReadOnly lang="json" value={testResponse} />
+      )}
       {(testResponse || options?.responseVariableMapping) && (
         <Accordion allowToggle allowMultiple>
           <AccordionItem>
diff --git a/apps/builder/components/shared/CodeEditor.tsx b/apps/builder/components/shared/CodeEditor.tsx
index 0145de8202..7d95292f2d 100644
--- a/apps/builder/components/shared/CodeEditor.tsx
+++ b/apps/builder/components/shared/CodeEditor.tsx
@@ -1,15 +1,18 @@
 import { Box, BoxProps } from '@chakra-ui/react'
 import { EditorState, EditorView, basicSetup } from '@codemirror/basic-setup'
 import { json } from '@codemirror/lang-json'
+import { css } from '@codemirror/lang-css'
 import { useEffect, useRef } from 'react'
 
 type Props = {
   value: string
+  lang: 'css' | 'json'
   onChange?: (value: string) => void
   isReadOnly?: boolean
 }
 export const CodeEditor = ({
   value,
+  lang,
   onChange,
   isReadOnly = false,
   ...props
@@ -31,14 +34,15 @@ export const CodeEditor = ({
       if (update.docChanged && onChange)
         onChange(update.state.doc.toJSON().join(' '))
     })
+    const extensions = [
+      updateListenerExtension,
+      basicSetup,
+      EditorState.readOnly.of(isReadOnly),
+    ]
+    extensions.push(lang === 'json' ? json() : css())
     const editor = new EditorView({
       state: EditorState.create({
-        extensions: [
-          updateListenerExtension,
-          basicSetup,
-          json(),
-          EditorState.readOnly.of(isReadOnly),
-        ],
+        extensions,
       }),
       parent: editorContainer.current,
     })
diff --git a/apps/builder/components/theme/CustomCssSettings/CustomCssSettings.tsx b/apps/builder/components/theme/CustomCssSettings/CustomCssSettings.tsx
new file mode 100644
index 0000000000..f876fee781
--- /dev/null
+++ b/apps/builder/components/theme/CustomCssSettings/CustomCssSettings.tsx
@@ -0,0 +1,17 @@
+import { CodeEditor } from 'components/shared/CodeEditor'
+import React from 'react'
+
+type Props = {
+  customCss?: string
+  onCustomCssChange: (css: string) => void
+}
+
+export const CustomCssSettings = ({ customCss, onCustomCssChange }: Props) => {
+  return (
+    <CodeEditor
+      value={customCss ?? ''}
+      lang="css"
+      onChange={onCustomCssChange}
+    />
+  )
+}
diff --git a/apps/builder/components/theme/SideMenu.tsx b/apps/builder/components/theme/SideMenu.tsx
index 71e71cdcd1..8c4eee3f0c 100644
--- a/apps/builder/components/theme/SideMenu.tsx
+++ b/apps/builder/components/theme/SideMenu.tsx
@@ -8,12 +8,13 @@ import {
   HStack,
   Stack,
 } from '@chakra-ui/react'
-import { ChatIcon, CodeIcon, LayoutIcon, PencilIcon } from 'assets/icons'
+import { ChatIcon, CodeIcon, PencilIcon } from 'assets/icons'
 import { headerHeight } from 'components/shared/TypebotHeader'
 import { useTypebot } from 'contexts/TypebotContext'
 import { ChatTheme, GeneralTheme } from 'models'
 import React from 'react'
 import { ChatThemeSettings } from './ChatSettings'
+import { CustomCssSettings } from './CustomCssSettings/CustomCssSettings'
 import { GeneralSettings } from './GeneralSettings'
 
 export const SideMenu = () => {
@@ -25,6 +26,9 @@ export const SideMenu = () => {
   const handleGeneralThemeChange = (general: GeneralTheme) =>
     updateTypebot({ theme: { ...typebot?.theme, general } })
 
+  const handleCustomCssChange = (customCss: string) =>
+    updateTypebot({ theme: { ...typebot?.theme, customCss } })
+
   return (
     <Stack
       flex="1"
@@ -55,21 +59,6 @@ export const SideMenu = () => {
             />
           </AccordionPanel>
         </AccordionItem>
-        <AccordionItem>
-          <AccordionButton py={6}>
-            <HStack flex="1" pl={2}>
-              <LayoutIcon />
-              <Heading fontSize="lg">Layout</Heading>
-            </HStack>
-            <AccordionIcon />
-          </AccordionButton>
-          <AccordionPanel pb={4}>
-            Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do
-            eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim
-            ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut
-            aliquip ex ea commodo consequat.
-          </AccordionPanel>
-        </AccordionItem>
         <AccordionItem>
           <AccordionButton py={6}>
             <HStack flex="1" pl={2}>
@@ -94,10 +83,10 @@ export const SideMenu = () => {
             <AccordionIcon />
           </AccordionButton>
           <AccordionPanel pb={4}>
-            Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do
-            eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim
-            ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut
-            aliquip ex ea commodo consequat.
+            <CustomCssSettings
+              customCss={typebot?.theme?.customCss}
+              onCustomCssChange={handleCustomCssChange}
+            />
           </AccordionPanel>
         </AccordionItem>
       </Accordion>
diff --git a/apps/builder/cypress/tests/theme/customCss.ts b/apps/builder/cypress/tests/theme/customCss.ts
new file mode 100644
index 0000000000..2fb1da2d4d
--- /dev/null
+++ b/apps/builder/cypress/tests/theme/customCss.ts
@@ -0,0 +1,26 @@
+import { getIframeBody } from 'cypress/support'
+
+describe('Custom CSS settings', () => {
+  beforeEach(() => {
+    cy.task('seed')
+    cy.signOut()
+  })
+
+  it('should reflect changes in real time', () => {
+    cy.loadTypebotFixtureInDatabase('typebots/theme/theme.json')
+    cy.signIn('test2@gmail.com')
+    cy.visit('/typebots/typebot4/theme')
+    cy.findByRole('button', { name: 'Custom CSS' }).click()
+
+    cy.findByTestId('code-editor').type(
+      '.typebot-button {background-color: green}',
+      {
+        parseSpecialCharSequences: false,
+      }
+    )
+    getIframeBody()
+      .findByTestId('button')
+      .should('have.css', 'background-color')
+      .should('eq', 'rgb(0, 128, 0)')
+  })
+})
diff --git a/apps/builder/package.json b/apps/builder/package.json
index 90a536f5ea..54d22bb582 100644
--- a/apps/builder/package.json
+++ b/apps/builder/package.json
@@ -13,6 +13,7 @@
     "@chakra-ui/css-reset": "^1.1.1",
     "@chakra-ui/react": "^1.7.4",
     "@codemirror/basic-setup": "^0.19.1",
+    "@codemirror/lang-css": "^0.19.3",
     "@codemirror/lang-json": "^0.19.1",
     "@codemirror/text": "^0.19.6",
     "@dnd-kit/core": "^4.0.3",
diff --git a/packages/bot-engine/src/components/TypebotViewer.tsx b/packages/bot-engine/src/components/TypebotViewer.tsx
index 33cf000416..1330c2ede3 100644
--- a/packages/bot-engine/src/components/TypebotViewer.tsx
+++ b/packages/bot-engine/src/components/TypebotViewer.tsx
@@ -48,6 +48,7 @@ export const TypebotViewer = ({
           {phoneNumberInputStyle}
           {phoneSyle}
           {style}
+          {typebot.theme?.customCss}
         </style>
       }
       style={{ width: '100%', height: '100%', border: 'none' }}
diff --git a/packages/models/src/typebot/theme.ts b/packages/models/src/typebot/theme.ts
index fb027497b5..93c6f25553 100644
--- a/packages/models/src/typebot/theme.ts
+++ b/packages/models/src/typebot/theme.ts
@@ -1,6 +1,7 @@
 export type Theme = {
   general?: GeneralTheme
   chat?: ChatTheme
+  customCss?: string
 }
 
 export type GeneralTheme = {
diff --git a/yarn.lock b/yarn.lock
index e8a5e8f917..42aa11a5e4 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -811,7 +811,7 @@
     "@codemirror/state" "^0.19.0"
     "@codemirror/view" "^0.19.23"
 
-"@codemirror/highlight@^0.19.0":
+"@codemirror/highlight@^0.19.0", "@codemirror/highlight@^0.19.6":
   version "0.19.7"
   resolved "https://registry.yarnpkg.com/@codemirror/highlight/-/highlight-0.19.7.tgz#91a0c9994c759f5f153861e3aae74ff9e7c7c35b"
   integrity sha512-3W32hBCY0pbbv/xidismw+RDMKuIag+fo4kZIbD7WoRj+Ttcaxjf+vP6RttRHXLaaqbWh031lTeON8kMlDhMYw==
@@ -831,6 +831,17 @@
     "@codemirror/state" "^0.19.2"
     "@codemirror/view" "^0.19.0"
 
+"@codemirror/lang-css@^0.19.3":
+  version "0.19.3"
+  resolved "https://registry.yarnpkg.com/@codemirror/lang-css/-/lang-css-0.19.3.tgz#7a17adf78c6fcdab4ad5ee4e360631c41e949e4a"
+  integrity sha512-tyCUJR42/UlfOPLb94/p7dN+IPsYSIzHbAHP2KQHANj0I+Orqp+IyIOS++M8TuCX4zkWh9dvi8s92yy/Tn8Ifg==
+  dependencies:
+    "@codemirror/autocomplete" "^0.19.0"
+    "@codemirror/highlight" "^0.19.6"
+    "@codemirror/language" "^0.19.0"
+    "@codemirror/state" "^0.19.0"
+    "@lezer/css" "^0.15.2"
+
 "@codemirror/lang-json@^0.19.1":
   version "0.19.1"
   resolved "https://registry.yarnpkg.com/@codemirror/lang-json/-/lang-json-0.19.1.tgz#616588d1422529965243c10af6c44ad0b9134fb0"
@@ -1338,6 +1349,13 @@
   resolved "https://registry.yarnpkg.com/@lezer/common/-/common-0.15.11.tgz#965b5067036305f12e8a3efc344076850be1d3a8"
   integrity sha512-vv0nSdIaVCRcJ8rPuDdsrNVfBOYe/4Szr/LhF929XyDmBndLDuWiCCHooGlGlJfzELyO608AyDhVsuX/ZG36NA==
 
+"@lezer/css@^0.15.2":
+  version "0.15.2"
+  resolved "https://registry.yarnpkg.com/@lezer/css/-/css-0.15.2.tgz#e96995da67df90bb4b191aaa8a486349cca5d8e7"
+  integrity sha512-tnMOMZY0Zs6JQeVjqfmREYMV0GnmZR1NitndLWioZMD6mA7VQF/PPKPmJX1f+ZgVZQc5Am0df9mX3aiJnNJlKQ==
+  dependencies:
+    "@lezer/lr" "^0.15.0"
+
 "@lezer/json@^0.15.0":
   version "0.15.0"
   resolved "https://registry.yarnpkg.com/@lezer/json/-/json-0.15.0.tgz#b96c1161eb8514e05f4eaaec95c68376e76e539f"