diff --git a/frontend/src/__tests__/App.spec.ts b/frontend/src/__tests__/App.spec.ts
new file mode 100644
index 0000000..579492b
--- /dev/null
+++ b/frontend/src/__tests__/App.spec.ts
@@ -0,0 +1,17 @@
+import { describe, it, expect } from 'vitest'
+import { mount } from '@vue/test-utils'
+import App from '@/App.vue'
+import router from '@/router'
+
+describe('App', () => {
+  it('renders RouterView with HomePage content', async () => {
+    router.push('/')
+    await router.isReady()
+    const wrapper = mount(App, {
+      global: {
+        plugins: [router],
+      },
+    })
+    expect(wrapper.text()).toContain('BilHälsning')
+  })
+})
diff --git a/frontend/src/__tests__/PlateInput.spec.ts b/frontend/src/__tests__/PlateInput.spec.ts
new file mode 100644
index 0000000..a009543
--- /dev/null
+++ b/frontend/src/__tests__/PlateInput.spec.ts
@@ -0,0 +1,102 @@
+import { describe, it, expect } from 'vitest'
+import { mount } from '@vue/test-utils'
+import PlateInput from '@/components/PlateInput.vue'
+
+function createWrapper(modelValue = '') {
+  return mount(PlateInput, {
+    props: { modelValue },
+  })
+}
+
+describe('PlateInput', () => {
+  it('renders an input element', () => {
+    const wrapper = createWrapper()
+    expect(wrapper.find('input').exists()).toBe(true)
+  })
+
+  it('auto-uppercases lowercase input', async () => {
+    const wrapper = createWrapper()
+    const input = wrapper.find('input')
+    await input.setValue('abc123')
+    expect(wrapper.emitted('update:modelValue')?.[0]).toEqual(['ABC123'])
+  })
+
+  it('strips non-alphanumeric characters', async () => {
+    const wrapper = createWrapper()
+    const input = wrapper.find('input')
+    await input.setValue('ABC 123')
+    expect(wrapper.emitted('update:modelValue')?.[0]).toEqual(['ABC123'])
+  })
+
+  it('strips dashes and symbols', async () => {
+    const wrapper = createWrapper()
+    const input = wrapper.find('input')
+    await input.setValue('ABC-12D')
+    expect(wrapper.emitted('update:modelValue')?.[0]).toEqual(['ABC12D'])
+  })
+
+  it('shows error message for invalid format after input', async () => {
+    const wrapper = createWrapper()
+    const input = wrapper.find('input')
+    await input.setValue('ABC12')
+    expect(wrapper.text()).toContain('giltigt registreringsnummer')
+  })
+
+  it('does not show error when input is empty', () => {
+    const wrapper = createWrapper()
+    expect(wrapper.text()).not.toContain('giltigt registreringsnummer')
+  })
+
+  it('emits lookup on valid ABC123 format', async () => {
+    const wrapper = createWrapper()
+    const input = wrapper.find('input')
+    await input.setValue('ABC123')
+    expect(wrapper.emitted('lookup')).toBeTruthy()
+    expect(wrapper.emitted('lookup')?.[0]).toEqual(['ABC123'])
+  })
+
+  it('emits lookup on valid ABC12D format', async () => {
+    const wrapper = createWrapper()
+    const input = wrapper.find('input')
+    await input.setValue('ABC12D')
+    expect(wrapper.emitted('lookup')).toBeTruthy()
+    expect(wrapper.emitted('lookup')?.[0]).toEqual(['ABC12D'])
+  })
+
+  it('does not emit lookup on invalid input', async () => {
+    const wrapper = createWrapper()
+    const input = wrapper.find('input')
+    await input.setValue('ABC1')
+    expect(wrapper.emitted('lookup')).toBeFalsy()
+  })
+
+  it('updates modelValue via v-model', async () => {
+    const wrapper = createWrapper()
+    const input = wrapper.find('input')
+    await input.setValue('ABC123')
+    expect(wrapper.emitted('update:modelValue')).toBeTruthy()
+    expect(wrapper.emitted('update:modelValue')?.[0]).toEqual(['ABC123'])
+  })
+
+  it('prevents re-emission for the same plate', async () => {
+    const wrapper = createWrapper()
+    const input = wrapper.find('input')
+    await input.setValue('ABC123')
+    expect(wrapper.emitted('lookup')).toHaveLength(1)
+    await input.setValue('ABC12')
+    expect(wrapper.emitted('lookup')).toHaveLength(1)
+    await input.setValue('ABC123')
+    expect(wrapper.emitted('lookup')).toHaveLength(1)
+  })
+
+  it('emits again for a different valid plate', async () => {
+    const wrapper = createWrapper()
+    const input = wrapper.find('input')
+    await input.setValue('ABC123')
+    expect(wrapper.emitted('lookup')).toHaveLength(1)
+    await input.setValue('')
+    await input.setValue('DEF456')
+    expect(wrapper.emitted('lookup')).toHaveLength(2)
+    expect(wrapper.emitted('lookup')?.[1]).toEqual(['DEF456'])
+  })
+})
diff --git a/frontend/src/__tests__/Router.spec.ts b/frontend/src/__tests__/Router.spec.ts
new file mode 100644
index 0000000..e27c96f
--- /dev/null
+++ b/frontend/src/__tests__/Router.spec.ts
@@ -0,0 +1,16 @@
+import { describe, it, expect } from 'vitest'
+import router from '@/router'
+
+describe('Router', () => {
+  it('resolves / to HomePage', async () => {
+    await router.push('/')
+    await router.isReady()
+    expect(router.currentRoute.value.name).toBe('home')
+  })
+
+  it('does not crash on unknown route', async () => {
+    await router.push('/nonexistent')
+    await router.isReady()
+    expect(router.currentRoute.value.matched.length).toBe(0)
+  })
+})
diff --git a/frontend/src/__tests__/Store.spec.ts b/frontend/src/__tests__/Store.spec.ts
new file mode 100644
index 0000000..ab732aa
--- /dev/null
+++ b/frontend/src/__tests__/Store.spec.ts
@@ -0,0 +1,10 @@
+import { describe, it, expect } from 'vitest'
+import { createPinia } from 'pinia'
+
+describe('Pinia', () => {
+  it('creates a Pinia instance', () => {
+    const pinia = createPinia()
+    expect(pinia).toBeDefined()
+    expect(pinia.state).toBeDefined()
+  })
+})
diff --git a/frontend/src/components/PlateInput.vue b/frontend/src/components/PlateInput.vue
new file mode 100644
index 0000000..3365035
--- /dev/null
+++ b/frontend/src/components/PlateInput.vue
@@ -0,0 +1,106 @@
+<script setup lang="ts">
+import { ref, computed, watch } from 'vue'
+
+const plate = defineModel<string>({ required: true })
+
+const emit = defineEmits<{
+  (e: 'lookup', plate: string): void
+}>()
+
+const touched = ref(false)
+const lastEmitted = ref('')
+
+const SWEDISH_PLATE_REGEX = /^[A-Z]{3}(\d{3}|\d{2}[A-Z])$/
+
+const isValid = computed(() => SWEDISH_PLATE_REGEX.test(plate.value ?? ''))
+
+const showError = computed(
+  () => touched.value && !isValid.value && (plate.value?.length ?? 0) > 0,
+)
+
+function handleInput(event: Event) {
+  const target = event.target as HTMLInputElement
+  const rawValue = target.value
+  const transformed = rawValue.toUpperCase().replace(/[^A-Z0-9]/g, '')
+  plate.value = transformed
+  touched.value = true
+}
+
+watch(isValid, (valid) => {
+  if (valid && plate.value && plate.value !== lastEmitted.value) {
+    lastEmitted.value = plate.value
+    emit('lookup', plate.value)
+  }
+})
+</script>
+
+<template>
+  <div class="plate-input">
+    <label for="plate" class="plate-input__label">Registreringsnummer</label>
+    <input
+      id="plate"
+      type="text"
+      inputmode="text"
+      autocomplete="off"
+      spellcheck="false"
+      :value="plate"
+      class="plate-input__field"
+      :class="{ 'plate-input__field--error': showError }"
+      placeholder="ABC 123"
+      maxlength="7"
+      @input="handleInput"
+    />
+    <p v-if="showError" class="plate-input__error">
+      Ange ett giltigt registreringsnummer
+    </p>
+  </div>
+</template>
+
+<style scoped>
+.plate-input {
+  display: flex;
+  flex-direction: column;
+  gap: 0.5rem;
+  width: 100%;
+}
+
+.plate-input__label {
+  font-size: 0.875rem;
+  font-weight: 500;
+  color: #4a5568;
+}
+
+.plate-input__field {
+  width: 100%;
+  padding: 0.875rem 1rem;
+  font-size: 1.5rem;
+  font-family: monospace;
+  letter-spacing: 0.15em;
+  text-transform: uppercase;
+  border: 2px solid #cbd5e0;
+  border-radius: 0.5rem;
+  outline: none;
+  transition: border-color 0.15s ease;
+  box-sizing: border-box;
+}
+
+.plate-input__field:focus {
+  border-color: #4299e1;
+  box-shadow: 0 0 0 3px rgba(66, 153, 225, 0.25);
+}
+
+.plate-input__field--error {
+  border-color: #e53e3e;
+}
+
+.plate-input__field--error:focus {
+  border-color: #e53e3e;
+  box-shadow: 0 0 0 3px rgba(229, 62, 62, 0.25);
+}
+
+.plate-input__error {
+  margin: 0;
+  font-size: 0.8125rem;
+  color: #e53e3e;
+}
+</style>
diff --git a/frontend/src/pages/HomePage.vue b/frontend/src/pages/HomePage.vue
index 54500d2..b08745d 100644
--- a/frontend/src/pages/HomePage.vue
+++ b/frontend/src/pages/HomePage.vue
@@ -1,9 +1,107 @@
-<script setup lang="ts"></script>
+<script setup lang="ts">
+import { ref } from 'vue'
+import PlateInput from '@/components/PlateInput.vue'
+
+interface VehicleInfo {
+  make: string
+  model: string
+  year: number
+  color: string
+}
+
+const FAKE_VEHICLES: Record<string, VehicleInfo> = {
+  ABC123: { make: 'Volvo', model: 'V70', year: 2009, color: 'Silver' },
+  ABC12D: { make: 'Volkswagen', model: 'Golf', year: 2020, color: 'Blå' },
+  XYZ789: { make: 'Saab', model: '9-3', year: 2005, color: 'Röd' },
+}
+
+const plate = ref('')
+const vehicle = ref<VehicleInfo | null>(null)
+const notFound = ref(false)
+const lookingUp = ref(false)
+
+function handleLookup(lookedUpPlate: string) {
+  lookingUp.value = true
+  notFound.value = false
+  vehicle.value = null
+
+  setTimeout(() => {
+    const found = FAKE_VEHICLES[lookedUpPlate]
+    if (found) {
+      vehicle.value = found
+      notFound.value = false
+    } else {
+      vehicle.value = null
+      notFound.value = true
+    }
+    lookingUp.value = false
+  }, 400)
+}
+</script>
 
 <template>
-  <div>
+  <div class="home">
     <h1>BilHälsning</h1>
+    <p class="home__subtitle">Skicka ett brev till en fordonsägare</p>
+
+    <PlateInput v-model="plate" @lookup="handleLookup" />
+
+    <div v-if="lookingUp" class="home__status">Söker...</div>
+
+    <div v-else-if="vehicle" class="home__vehicle">
+      <p class="home__vehicle-text">
+        {{ vehicle.make }} {{ vehicle.model }} ({{ vehicle.year }}) &mdash;
+        {{ vehicle.color }}
+      </p>
+    </div>
+
+    <div v-else-if="notFound" class="home__not-found">
+      <p>Inget fordon hittades för {{ plate }}</p>
+    </div>
   </div>
 </template>
 
-<style scoped></style>
+<style scoped>
+.home {
+  max-width: 28rem;
+  margin: 3rem auto 0;
+  padding: 0 1rem;
+}
+
+.home__subtitle {
+  color: #718096;
+  margin: 0 0 1.5rem 0;
+}
+
+.home__status {
+  margin-top: 0.75rem;
+  color: #718096;
+  font-size: 0.875rem;
+}
+
+.home__vehicle {
+  margin-top: 0.75rem;
+  padding: 1rem;
+  background: #f0fff4;
+  border: 1px solid #c6f6d5;
+  border-radius: 0.5rem;
+}
+
+.home__vehicle-text {
+  margin: 0;
+  font-weight: 500;
+}
+
+.home__not-found {
+  margin-top: 0.75rem;
+  padding: 1rem;
+  background: #fffaf0;
+  border: 1px solid #feebc8;
+  border-radius: 0.5rem;
+}
+
+.home__not-found p {
+  margin: 0;
+  color: #c05621;
+}
+</style>
diff --git a/frontend/src/stores/.gitkeep b/frontend/src/stores/.gitkeep
deleted file mode 100644
index e69de29..0000000