diff --git a/package-lock.json b/package-lock.json
index 84a4c3a2..330c0ecf 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -10,6 +10,7 @@
       "dependencies": {
         "@tailwindcss/vite": "^4.2.2",
         "canvas-confetti": "^1.9.4",
+        "leo-profanity": "^1.9.0",
         "lucide-vue-next": "^1.0.0",
         "pinia": "^3.0.4",
         "tailwindcss": "^4.2.2",
@@ -3509,6 +3510,13 @@
         "url": "https://github.com/sponsors/isaacs"
       }
     },
+    "node_modules/french-badwords-list": {
+      "version": "1.0.7",
+      "resolved": "https://registry.npmjs.org/french-badwords-list/-/french-badwords-list-1.0.7.tgz",
+      "integrity": "sha512-H1ziKs2PJh2+UXZ9oCGJ/rRQpsI9NBykGf2Sc7WaKaj1OnWFuBXfsvANTdRcfVmOghGQaUmRyZ1hJOPbDpy04Q==",
+      "license": "MIT",
+      "optional": true
+    },
     "node_modules/fsevents": {
       "version": "2.3.2",
       "resolved": "https://registry.npmjs.org/fsevents/-/fsevents-2.3.2.tgz",
@@ -3919,6 +3927,19 @@
         "json-buffer": "3.0.1"
       }
     },
+    "node_modules/leo-profanity": {
+      "version": "1.9.0",
+      "resolved": "https://registry.npmjs.org/leo-profanity/-/leo-profanity-1.9.0.tgz",
+      "integrity": "sha512-vMrrrjsbT+fA5I/1rlBEVT5YjJsw1ASIVF8/xBEdZ6ylsg5AEIBrEvHxwe5XAmfVuTBi7aw2KcO2L3s9ddpKzw==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=18"
+      },
+      "optionalDependencies": {
+        "french-badwords-list": "^1.0.7",
+        "russian-bad-words": "^0.5.0"
+      }
+    },
     "node_modules/levn": {
       "version": "0.4.1",
       "resolved": "https://registry.npmjs.org/levn/-/levn-0.4.1.tgz",
@@ -5033,6 +5054,16 @@
         "queue-microtask": "^1.2.2"
       }
     },
+    "node_modules/russian-bad-words": {
+      "version": "0.5.0",
+      "resolved": "https://registry.npmjs.org/russian-bad-words/-/russian-bad-words-0.5.0.tgz",
+      "integrity": "sha512-euNvEYki6iYYpkNbeudW+lEMMYGEmN7EBwVF8ezlbv0bZoQpVYB7W10cCeUIGV7Ed50sJynLQ0c559q5iI0ejQ==",
+      "license": "MIT",
+      "optional": true,
+      "engines": {
+        "node": ">=10"
+      }
+    },
     "node_modules/sax": {
       "version": "1.6.0",
       "resolved": "https://registry.npmjs.org/sax/-/sax-1.6.0.tgz",
diff --git a/package.json b/package.json
index 4debe6d3..a0f74bbe 100644
--- a/package.json
+++ b/package.json
@@ -23,6 +23,7 @@
   "dependencies": {
     "@tailwindcss/vite": "^4.2.2",
     "canvas-confetti": "^1.9.4",
+    "leo-profanity": "^1.9.0",
     "lucide-vue-next": "^1.0.0",
     "pinia": "^3.0.4",
     "tailwindcss": "^4.2.2",
diff --git a/src/classrooms/pages/ClassroomModerationPage.vue b/src/classrooms/pages/ClassroomModerationPage.vue
index e4a5c843..0e8f6c04 100644
--- a/src/classrooms/pages/ClassroomModerationPage.vue
+++ b/src/classrooms/pages/ClassroomModerationPage.vue
@@ -10,6 +10,7 @@ import {
   requestUpdateTeacherClassroomBannedWord,
   type ClassroomBannedWordResponse,
 } from '@/shared/moderation/moderation.api'
+import { useProfanityFilter } from '@/shared/composables/useProfanityFilter'
 
 const route = useRoute()
 const { t } = useI18n()
@@ -22,6 +23,7 @@ const errorMessage = ref<string | null>(null)
 const newWord = ref('')
 const editingId = ref<number | null>(null)
 const editingWord = ref('')
+const { hasProfanity } = useProfanityFilter()
 
 const authorizationHeader = computed(() => authStore.authorizationHeader)
 
@@ -50,6 +52,10 @@ async function loadBannedWords() {
   }
 }
 
+function normalizeWord(word: string) {
+  return word.trim().toLowerCase()
+}
+
 function startEditing(entry: ClassroomBannedWordResponse) {
   editingId.value = entry.id
   editingWord.value = entry.word
@@ -66,12 +72,24 @@ async function createWord() {
     return
   }
 
-  const normalizedWord = newWord.value.trim()
+  const normalizedWord = normalizeWord(newWord.value)
+
   if (!normalizedWord) {
     errorMessage.value = t('classroomModeration.errors.missingWord')
     return
   }
 
+  if (hasProfanity(normalizedWord)) {
+    errorMessage.value = t('classroomModeration.errors.alreadyBlockedGlobally')
+    return
+  }
+
+  // avoid duplicates
+  if (bannedWords.value.some((w) => normalizeWord(w.word) === normalizedWord)) {
+    errorMessage.value = t('classroomModeration.errors.duplicateWord')
+    return
+  }
+
   status.value = 'saving'
   errorMessage.value = null
 
@@ -106,6 +124,19 @@ async function saveWord(entryId: number) {
     return
   }
 
+  if (hasProfanity(normalizedWord)) {
+    errorMessage.value = t('classroomModeration.errors.alreadyBlockedGlobally')
+    return
+  }
+  if (
+    bannedWords.value.some(
+      (w) => w.id !== entryId && normalizeWord(w.word) === normalizedWord,
+    )
+  ) {
+    errorMessage.value = t('classroomModeration.errors.duplicateWord')
+    return
+  }
+
   status.value = 'saving'
   errorMessage.value = null
 
@@ -167,7 +198,7 @@ onMounted(() => {
 
 <template>
   <main
-    class="mx-auto flex min-h-screen w-full max-w-5xl flex-col gap-6 px-6 py-10"
+    class="mx-auto flex min-h-screen w-full max-w-5xl flex-col gap-6 px-6 py-10 pt-30"
   >
     <header class="space-y-2">
       <h1 class="text-4xl font-extrabold text-zinc-900">
diff --git a/src/locales/en.ts b/src/locales/en.ts
index 22472043..caca874a 100644
--- a/src/locales/en.ts
+++ b/src/locales/en.ts
@@ -452,6 +452,7 @@ export const en = {
     namePlaceholder: 'Detective name',
     nameUpdateSuccess: 'Display name updated.',
     nameUpdateError: 'Could not update the display name.',
+    nameProfanityError: 'Display name cannot contain banned words',
     avatarTitle: 'Avatar',
     avatarPlaceholder:
       'The avatar builder is not fully implemented yet, but this is where avatar editing belongs.',
@@ -1059,7 +1060,7 @@ export const en = {
   classroomModeration: {
     title: 'Word filter',
     description:
-      'Add, edit, and remove words that should be blocked in pupil text.',
+      'Add, edit, and remove words that should be blocked in pupil text. Typical profanities are blocked automatically.',
     addLabel: 'New word',
     addPlaceholder: 'Enter a word or phrase',
     addAction: 'Add',
@@ -1075,6 +1076,8 @@ export const en = {
       update: 'Could not update the word.',
       delete: 'Could not delete the word.',
       missingWord: 'Enter a word before saving.',
+      alreadyBlockedGlobally: 'This word is already blocked globally.',
+      duplicateWord: 'This word has already been blocked.',
     },
   },
   mystery: {
diff --git a/src/locales/nb.ts b/src/locales/nb.ts
index 822644f3..9084a25b 100644
--- a/src/locales/nb.ts
+++ b/src/locales/nb.ts
@@ -565,6 +565,7 @@ export const nb = {
       namePlaceholder: 'Detektivnavn',
       nameUpdateSuccess: 'Visningsnavnet er oppdatert.',
       nameUpdateError: 'Kunne ikke oppdatere visningsnavnet.',
+      nameProfanityError: 'Navnet kan ikke inneholde forbudte ord',
       avatarTitle: 'Avatar',
       avatarPlaceholder:
         'Avatarbyggeren er ikke fullt implementert ennå, men dette er stedet for avatarredigering.',
@@ -1101,7 +1102,7 @@ export const nb = {
   classroomModeration: {
     title: 'Ordfilter',
     description:
-      'Legg til, endre og fjern ord som skal blokkeres i elevtekster.',
+      'Legg til, endre og fjern ord som skal blokkeres i elevtekster. Typiske banneord er automatisk blokkerte.',
     addLabel: 'Nytt ord',
     addPlaceholder: 'Skriv inn ord eller uttrykk',
     addAction: 'Legg til',
@@ -1117,6 +1118,8 @@ export const nb = {
       update: 'Kunne ikke oppdatere ordet.',
       delete: 'Kunne ikke slette ordet.',
       missingWord: 'Skriv inn et ord før du lagrer.',
+      alreadyBlockedGlobally: 'Ordet er allerede blokkert globalt.',
+      duplicateWord: 'Ordet har allerede blitt blokkert.',
     },
   },
   pendingApproval: {
diff --git a/src/mystery/components/MysterySubmissionForm.vue b/src/mystery/components/MysterySubmissionForm.vue
index 98c4d770..5b699629 100644
--- a/src/mystery/components/MysterySubmissionForm.vue
+++ b/src/mystery/components/MysterySubmissionForm.vue
@@ -2,8 +2,10 @@
 import { computed, ref } from 'vue'
 import { useI18n } from 'vue-i18n'
 import { moderateText } from '@/shared/moderation/banned-words'
+import { useProfanityFilter } from '@/shared/composables/useProfanityFilter.ts'
 
 const { t } = useI18n()
+const { hasProfanity } = useProfanityFilter()
 
 const props = defineProps<{
   submitting: boolean
@@ -22,21 +24,33 @@ const description = ref('')
 const attachmentFile = ref<File | null>(null)
 const attachmentPreviewUrl = ref<string | null>(null)
 const uploadError = ref<string | null>(null)
-const moderation = computed(() =>
-  moderateText([description.value], props.bannedWords ?? []),
-)
-const moderationError = computed(() =>
-  moderation.value.hasBlockedWords
-    ? t('mystery.submitForm.bannedWords', {
-        words: moderation.value.blockedWords.join(', '),
-      })
-    : null,
-)
+
+const moderation = computed(() => {
+  const text = description.value
+  const bannedCheck = moderateText([text], props.bannedWords ?? [])
+  const profanityDetected = hasProfanity(text)
+  return {
+    ...bannedCheck,
+    hasProfanity: profanityDetected,
+    hasAnyViolation: bannedCheck.hasBlockedWords || profanityDetected,
+  }
+})
+const moderationError = computed(() => {
+  if (moderation.value.hasBlockedWords) {
+    return t('mystery.submitForm.bannedWords', {
+      words: moderation.value.blockedWords.join(', '),
+    })
+  }
+  if (moderation.value.hasProfanity) {
+    return t('mystery.submitForm.bannedWords')
+  }
+  return null
+})
 
 const canSubmit = () =>
   description.value.trim().length > 0 &&
   !uploadError.value &&
-  !moderation.value.hasBlockedWords
+  !moderation.value.hasAnyViolation
 
 function onFileSelected(event: Event) {
   const input = event.target as HTMLInputElement
diff --git a/src/notebook/components/NotebookComponent.vue b/src/notebook/components/NotebookComponent.vue
index 684fc015..c4ddce87 100644
--- a/src/notebook/components/NotebookComponent.vue
+++ b/src/notebook/components/NotebookComponent.vue
@@ -29,6 +29,7 @@ import type {
 } from '@/notebook/model/notebook.types'
 import { requestClassroomBannedWords } from '@/shared/moderation/moderation.api'
 import { moderateText } from '@/shared/moderation/banned-words'
+import { useProfanityFilter } from '@/shared/composables/useProfanityFilter.ts'
 
 const authStore = useAuthStore()
 const { t } = useI18n()
@@ -54,6 +55,7 @@ const errorMessage = ref<string | null>(null)
 const newEntryTitle = ref('')
 const newEntryContent = ref('')
 const bannedWords = ref<string[]>([])
+const { hasProfanity } = useProfanityFilter()
 const currentPageByStopId = ref<Record<number, number>>({})
 const pageBodyElement = ref<HTMLElement | null>(null)
 const formElement = ref<HTMLElement | null>(null)
@@ -134,16 +136,31 @@ const entriesByStopId = computed(() =>
 const defaultCreateStopId = computed(
   () => currentStopId.value ?? mapStops.value[0]?.stopId ?? null,
 )
-const notebookModeration = computed(() =>
-  moderateText([newEntryTitle.value, newEntryContent.value], bannedWords.value),
-)
-const notebookModerationMessage = computed(() =>
-  notebookModeration.value.hasBlockedWords
-    ? t('notebook.errors.bannedWords', {
-        words: notebookModeration.value.blockedWords.join(', '),
-      })
-    : null,
-)
+
+const notebookModeration = computed(() => {
+  const title = newEntryTitle.value
+  const content = newEntryContent.value
+  const bannedCheck = moderateText([title, content], bannedWords.value)
+  const profanityDetected = hasProfanity(title) || hasProfanity(content)
+  return {
+    ...bannedCheck,
+    hasProfanity: profanityDetected,
+    hasAnyViolation: bannedCheck.hasBlockedWords || profanityDetected,
+  }
+})
+
+const notebookModerationMessage = computed(() => {
+  if (notebookModeration.value.hasBlockedWords) {
+    return t('notebook.errors.bannedWords', {
+      words: notebookModeration.value.blockedWords.join(', '),
+    })
+  }
+  if (notebookModeration.value.hasProfanity) {
+    return t('notebook.errors.profanity')
+  }
+  return null
+})
+
 const pageCapacity = computed(() =>
   Math.max(availablePageHeight.value || defaultPageHeight, 220),
 )
@@ -361,7 +378,7 @@ async function createEntry() {
     return
   }
 
-  if (notebookModeration.value.hasBlockedWords) {
+  if (notebookModeration.value.hasAnyViolation) {
     status.value = 'error'
     errorMessage.value = notebookModerationMessage.value
     return
@@ -707,7 +724,8 @@ onBeforeUnmount(() => {
                     :disabled="
                       status === 'saving' ||
                       currentClassroomId === null ||
-                      defaultCreateStopId === null
+                      defaultCreateStopId === null ||
+                      notebookModeration.hasAnyViolation
                     "
                     type="submit"
                   >
diff --git a/src/profile/pages/PupilProfilePage.vue b/src/profile/pages/PupilProfilePage.vue
index 92254ecd..93b2cd69 100644
--- a/src/profile/pages/PupilProfilePage.vue
+++ b/src/profile/pages/PupilProfilePage.vue
@@ -6,6 +6,8 @@ import { useAuthStore } from '@/auth/model/auth.store'
 import AvatarComponent from '@/avatar/components/AvatarComponent.vue'
 import avatarBackground from '@/assets/avatar/background/avatar-background.png'
 import { requestUpdateCurrentUserProfile } from '@/profile/api/profile.api'
+import { requestClassroomBannedWords } from '@/shared/moderation/moderation.api.ts'
+import { useProfanityFilter } from '@/shared/composables/useProfanityFilter.ts'
 
 const { t } = useI18n()
 const authStore = useAuthStore()
@@ -29,6 +31,37 @@ const normalizedDraftDisplayName = computed(() =>
 const isNameDirty = computed(
   () => normalizedDraftDisplayName.value !== savedDisplayName.value,
 )
+const { hasProfanity } = useProfanityFilter()
+const bannedWords = ref<string[]>([])
+async function loadBannedWords() {
+  if (
+    !authStore.authorizationHeader ||
+    !pupilProfile.value?.currentClassroomId
+  ) {
+    bannedWords.value = []
+    return
+  }
+  try {
+    const result = await requestClassroomBannedWords(
+      pupilProfile.value.currentClassroomId,
+      authStore.authorizationHeader,
+    )
+    bannedWords.value = result.map((entry) => entry.word.toLowerCase())
+  } catch {
+    bannedWords.value = []
+  }
+}
+
+function containsBannedWord(text: string, words: string[]) {
+  const normalized = text.toLowerCase()
+  return words.some((word) => normalized.includes(word))
+}
+
+const hasBadWords = computed(() => {
+  const name = normalizedDraftDisplayName.value
+  return hasProfanity(name) || containsBannedWord(name, bannedWords.value)
+})
+
 const avatarPreviewStyle = computed(() => ({
   backgroundImage: `url(${avatarBackground})`,
   backgroundPosition: 'center',
@@ -44,6 +77,7 @@ watch(
     if (!isEditingName.value) {
       draftDisplayName.value = displayName
     }
+    void loadBannedWords()
   },
   { immediate: true },
 )
@@ -89,6 +123,12 @@ async function saveDisplayName() {
   try {
     const updatedDisplayName = normalizedDraftDisplayName.value
 
+    if (hasProfanity(updatedDisplayName)) {
+      saveErrorMessage.value = t('pupilProfile.nameProfanityError')
+      isSavingName.value = false
+      return
+    }
+
     await requestUpdateCurrentUserProfile(authStore.authorizationHeader, {
       displayName: normalizedDraftDisplayName.value,
     })
@@ -192,7 +232,7 @@ onMounted(() => {
             <div class="flex flex-wrap gap-3">
               <button
                 class="inline-flex items-center justify-center rounded-lg border border-zinc-900 bg-zinc-900 px-4 py-3 text-white transition hover:bg-zinc-800 focus:outline-none focus:ring-2 focus:ring-zinc-900/20"
-                :disabled="!isNameDirty || isSavingName"
+                :disabled="!isNameDirty || isSavingName || hasBadWords"
                 type="submit"
               >
                 {{
@@ -212,6 +252,10 @@ onMounted(() => {
             </div>
           </form>
 
+          <p v-if="hasBadWords" class="text-sm text-red-600">
+            {{ t('pupilProfile.nameProfanityError') }}
+          </p>
+
           <p v-if="saveSuccessMessage" class="mt-4 text-sm text-emerald-700">
             {{ saveSuccessMessage }}
           </p>
diff --git a/src/shared/composables/useProfanityFilter.ts b/src/shared/composables/useProfanityFilter.ts
new file mode 100644
index 00000000..0f2f000f
--- /dev/null
+++ b/src/shared/composables/useProfanityFilter.ts
@@ -0,0 +1,42 @@
+import leoProfanity from 'leo-profanity'
+
+let initialized = false
+
+function init() {
+  if (initialized) return
+
+  leoProfanity.clearList()
+
+  leoProfanity.loadDictionary('en')
+
+  leoProfanity.add(['faen', 'jævlig', 'dritt', 'helvete', 'idiot'])
+
+  initialized = true
+}
+
+function normalize(text: string) {
+  return text
+    .toLowerCase()
+    .replace(/[@4]/g, 'a')
+    .replace(/[1!l|]/g, 'i')
+    .replace(/3/g, 'e')
+    .replace(/0/g, 'o')
+    .replace(/\s+/g, '')
+    .replace(/[^a-zæøå]/g, '')
+}
+export function useProfanityFilter() {
+  init()
+
+  function hasProfanity(text: string): boolean {
+    return leoProfanity.check(text) || leoProfanity.check(normalize(text))
+  }
+
+  function clean(text: string): string {
+    return leoProfanity.clean(text)
+  }
+
+  return {
+    hasProfanity,
+    clean,
+  }
+}