diff --git a/src/components/NoteConflictModal.vue b/src/components/NoteConflictModal.vue
new file mode 100644
index 0000000..21c0bf0
--- /dev/null
+++ b/src/components/NoteConflictModal.vue
@@ -0,0 +1,82 @@
+<script lang="ts" setup>
+import { onMounted, ref, watch } from "vue"
+
+const props = defineProps<{ open: boolean }>()
+
+const emit = defineEmits<{
+  (e: "discard"): void
+  (e: "overwrite"): void
+  (e: "cancel"): void
+  (e: "update:open", value: boolean): void
+}>()
+
+const dialogRef = ref<HTMLDialogElement | null>(null)
+
+const close = () => {
+  if (dialogRef.value?.open) dialogRef.value.close()
+  emit("update:open", false)
+}
+
+const choose = (action: "discard" | "overwrite" | "cancel") => {
+  emit(action)
+  close()
+}
+
+watch(
+  () => props.open,
+  (open) => {
+    const el = dialogRef.value
+    if (!el) return
+    if (open && !el.open) el.showModal()
+    else if (!open && el.open) el.close()
+  }
+)
+
+onMounted(() => {
+  if (props.open) dialogRef.value?.showModal()
+})
+</script>
+
+<template>
+  <dialog
+    ref="dialogRef"
+    class="modal"
+    @close="emit('update:open', false)"
+    @cancel.prevent="choose('cancel')"
+  >
+    <div class="modal-box">
+      <h3 class="text-lg font-bold">GitHub has a newer version of this note</h3>
+      <p class="py-3 text-sm">
+        Someone (or another device) updated this note on GitHub since you
+        started editing. If you save now, their changes will be overwritten.
+      </p>
+
+      <div class="modal-action flex-col gap-2 sm:flex-row sm:justify-end">
+        <button
+          type="button"
+          class="btn btn-ghost"
+          @click="choose('cancel')"
+        >
+          Cancel
+        </button>
+        <button
+          type="button"
+          class="btn btn-warning"
+          @click="choose('overwrite')"
+        >
+          Save anyway (overwrite)
+        </button>
+        <button
+          type="button"
+          class="btn btn-primary"
+          @click="choose('discard')"
+        >
+          Discard my edits, pull latest
+        </button>
+      </div>
+    </div>
+    <form method="dialog" class="modal-backdrop">
+      <button type="submit" @click="choose('cancel')">close</button>
+    </form>
+  </dialog>
+</template>
diff --git a/src/components/NoteFreshnessBadge.vue b/src/components/NoteFreshnessBadge.vue
new file mode 100644
index 0000000..9920d1c
--- /dev/null
+++ b/src/components/NoteFreshnessBadge.vue
@@ -0,0 +1,237 @@
+<script lang="ts" setup>
+import { computed } from "vue"
+
+import type { FreshnessStatus } from "@/hooks/useNoteFreshness.hook"
+
+const props = defineProps<{
+  status: FreshnessStatus
+  lastCheckedAt: Date | null
+}>()
+
+defineEmits<{ (e: "click"): void }>()
+
+const formatTime = (d: Date) =>
+  d.toLocaleTimeString(undefined, { hour: "2-digit", minute: "2-digit" })
+
+const minutesAgo = (d: Date) =>
+  Math.max(1, Math.round((Date.now() - d.getTime()) / 60000))
+
+const label = computed(() => {
+  switch (props.status) {
+    case "verified":
+      return "Up to date"
+    case "checking":
+      return "Checking…"
+    case "outdated":
+      return "Outdated"
+    case "stale-known":
+      return props.lastCheckedAt
+        ? `Checked ${minutesAgo(props.lastCheckedAt)}m ago`
+        : "Not checked"
+    case "offline":
+      return "Can’t reach GitHub"
+    case "unknown":
+    default:
+      return "Not checked"
+  }
+})
+
+const tooltip = computed(() => {
+  switch (props.status) {
+    case "verified":
+      return props.lastCheckedAt
+        ? `Verified at ${formatTime(props.lastCheckedAt)}. Click to re-check.`
+        : "Click to re-check."
+    case "outdated":
+      return "GitHub has a newer version. Click to pull latest."
+    case "stale-known":
+      return "Click to verify against GitHub."
+    case "offline":
+      return "Could not reach GitHub. Click to retry."
+    case "checking":
+      return "Checking against GitHub…"
+    case "unknown":
+    default:
+      return "Click to check against GitHub."
+  }
+})
+
+const stateClass = computed(() => `state-${props.status}`)
+const isBusy = computed(() => props.status === "checking")
+</script>
+
+<template>
+  <button
+    class="freshness button is-text is-light"
+    :class="stateClass"
+    :title="tooltip"
+    :aria-label="tooltip"
+    :disabled="isBusy"
+    @click="$emit('click')"
+  >
+    <svg
+      v-if="status === 'verified'"
+      xmlns="http://www.w3.org/2000/svg"
+      class="icon icon-tabler icon-tabler-cloud-check"
+      width="20"
+      height="20"
+      viewBox="0 0 24 24"
+      fill="none"
+      stroke="currentColor"
+      stroke-width="1.75"
+      stroke-linecap="round"
+      stroke-linejoin="round"
+    >
+      <path
+        d="M11 18.004h-4.343c-2.572 -.004 -4.657 -2.011 -4.657 -4.487c0 -2.475 2.085 -4.482 4.657 -4.482c.393 -1.762 1.794 -3.2 3.675 -3.773c1.88 -.572 3.956 -.193 5.444 1c1.488 1.19 2.162 3.007 1.77 4.769h.99c1.388 0 2.585 .82 3.138 2.007"
+      />
+      <path d="M15 19l2 2l4 -4" />
+    </svg>
+    <svg
+      v-else-if="status === 'unknown' || status === 'stale-known'"
+      xmlns="http://www.w3.org/2000/svg"
+      class="icon icon-tabler"
+      :class="
+        status === 'stale-known'
+          ? 'icon-tabler-clock'
+          : 'icon-tabler-cloud-question'
+      "
+      width="20"
+      height="20"
+      viewBox="0 0 24 24"
+      fill="none"
+      stroke="currentColor"
+      stroke-width="1.75"
+      stroke-linecap="round"
+      stroke-linejoin="round"
+    >
+      <template v-if="status === 'stale-known'">
+        <path d="M3 12a9 9 0 1 0 18 0a9 9 0 0 0 -18 0" />
+        <path d="M12 7v5l3 3" />
+      </template>
+      <template v-else>
+        <path
+          d="M14.5 18.004h-7.843c-2.572 -.004 -4.657 -2.011 -4.657 -4.487c0 -2.475 2.085 -4.482 4.657 -4.482c.393 -1.762 1.794 -3.2 3.675 -3.773c1.88 -.572 3.956 -.193 5.444 1c1.488 1.19 2.162 3.007 1.77 4.769h.99"
+        />
+        <path d="M19 22v.01" />
+        <path
+          d="M19 19a2.003 2.003 0 0 0 .914 -3.782a1.98 1.98 0 0 0 -2.414 .483"
+        />
+      </template>
+    </svg>
+    <svg
+      v-else-if="status === 'outdated'"
+      xmlns="http://www.w3.org/2000/svg"
+      class="icon icon-tabler icon-tabler-cloud-download"
+      width="20"
+      height="20"
+      viewBox="0 0 24 24"
+      fill="none"
+      stroke="currentColor"
+      stroke-width="1.75"
+      stroke-linecap="round"
+      stroke-linejoin="round"
+    >
+      <path
+        d="M19 18a3.5 3.5 0 0 0 0 -7h-1a5 4.5 0 0 0 -11 -2a4.6 4.4 0 0 0 -2.1 8.4"
+      />
+      <path d="M12 13l0 9" />
+      <path d="M9 19l3 3l3 -3" />
+    </svg>
+    <svg
+      v-else-if="status === 'checking'"
+      xmlns="http://www.w3.org/2000/svg"
+      class="icon icon-tabler icon-tabler-loader-2 spin"
+      width="20"
+      height="20"
+      viewBox="0 0 24 24"
+      fill="none"
+      stroke="currentColor"
+      stroke-width="1.75"
+      stroke-linecap="round"
+      stroke-linejoin="round"
+    >
+      <path d="M12 3a9 9 0 1 0 9 9" />
+    </svg>
+    <svg
+      v-else
+      xmlns="http://www.w3.org/2000/svg"
+      class="icon icon-tabler icon-tabler-cloud-off"
+      width="20"
+      height="20"
+      viewBox="0 0 24 24"
+      fill="none"
+      stroke="currentColor"
+      stroke-width="1.75"
+      stroke-linecap="round"
+      stroke-linejoin="round"
+    >
+      <path
+        d="M9.58 5.548c.24 -.11 .492 -.207 .752 -.286c1.88 -.572 3.956 -.193 5.444 1c1.488 1.19 2.162 3.007 1.77 4.769h.99c1.913 0 3.464 1.56 3.464 3.486c0 .957 -.383 1.824 -1.003 2.454m-2.997 1.033h-11.343c-2.572 -.004 -4.657 -2.011 -4.657 -4.487c0 -2.475 2.085 -4.482 4.657 -4.482c.13 -.582 .37 -1.128 .7 -1.62"
+      />
+      <path d="M3 3l18 18" />
+    </svg>
+    <span class="freshness-label">{{ label }}</span>
+  </button>
+</template>
+
+<style lang="scss" scoped>
+.freshness {
+  display: inline-flex;
+  align-items: center;
+  gap: 0.35rem;
+  font-size: 0.75rem;
+  padding: 0.15rem 0.5rem;
+  background: transparent;
+  border: 0;
+  cursor: pointer;
+  vertical-align: middle;
+
+  &[disabled] {
+    cursor: progress;
+  }
+
+  .icon {
+    flex-shrink: 0;
+  }
+
+  .freshness-label {
+    line-height: 1;
+  }
+}
+
+.state-verified {
+  color: var(--color-success, hsl(140, 60%, 35%));
+}
+
+.state-outdated {
+  color: var(--color-warning, hsl(35, 90%, 45%));
+}
+
+.state-offline {
+  color: var(--color-error, hsl(0, 70%, 45%));
+}
+
+.state-unknown,
+.state-stale-known,
+.state-checking {
+  color: var(--color-base-content);
+  opacity: 0.6;
+}
+
+.spin {
+  animation: freshness-spin 1s linear infinite;
+}
+
+@keyframes freshness-spin {
+  to {
+    transform: rotate(360deg);
+  }
+}
+
+@media screen and (max-width: 768px) {
+  .freshness-label {
+    display: none;
+  }
+}
+</style>
diff --git a/src/components/StackedNote.vue b/src/components/StackedNote.vue
index 573afab..dd1864c 100644
--- a/src/components/StackedNote.vue
+++ b/src/components/StackedNote.vue
@@ -18,6 +18,7 @@ import {
   runMermaid,
   useShikiji
 } from "@/hooks/useMarkdown.hook"
+import { useNoteFreshness } from "@/hooks/useNoteFreshness.hook"
 import { useNoteOverlay } from "@/hooks/useNoteOverlay.hook"
 import { useRouteQueryStackedNotes } from "@/hooks/useRouteQueryStackedNotes.hook"
 import { useTitleNotes } from "@/hooks/useTitleNotes.hook"
@@ -30,6 +31,14 @@ const LinkedNotes = defineAsyncComponent(
   () => import("@/components/LinkedNotes.vue")
 )
 
+const NoteFreshnessBadge = defineAsyncComponent(
+  () => import("@/components/NoteFreshnessBadge.vue")
+)
+
+const NoteConflictModal = defineAsyncComponent(
+  () => import("@/components/NoteConflictModal.vue")
+)
+
 const EditNote = defineAsyncComponent(
   () => import("@/modules/note/components/EditNote.vue")
 )
@@ -104,10 +113,34 @@ const { updateFile } = useGitHubContent({
   repo: repo.value
 })
 
+const {
+  status: freshnessStatus,
+  lastCheckedAt,
+  latestSha,
+  check: checkFreshness,
+  pullLatest
+} = useNoteFreshness({
+  user: user.value,
+  repo: repo.value,
+  sha,
+  path,
+  getEditedSha
+})
+
+const conflictOpen = ref(false)
+
 onMounted(async () => {
   initialRawContent.value = await getRawContent()
 })
 
+watch(
+  path,
+  (p) => {
+    if (p) void checkFreshness()
+  },
+  { immediate: true }
+)
+
 const { mode, toggleMode } = useEditionMode()
 
 watch([content, mode], () => {
@@ -132,7 +165,43 @@ watch([content, mode], () => {
   })
 })
 
+const performSave = async (overrideSha?: string) => {
+  if (!path.value) {
+    console.warn("no path found for this file")
+    return
+  }
+
+  const editedSha = overrideSha ?? (await getEditedSha()) ?? sha.value
+  const { sha: newSha, conflict } = await updateFile({
+    content: rawContent.value,
+    path: path.value,
+    sha: editedSha
+  })
+
+  if (conflict) {
+    await checkFreshness()
+    conflictOpen.value = true
+    if (mode.value === "read") toggleMode()
+    return
+  }
+
+  if (!newSha) {
+    console.warn("no new SHA found for this file")
+    return
+  }
+
+  await saveCacheNote(encodeUTF8ToBase64(rawContent.value), {
+    editedSha: newSha
+  })
+  initialRawContent.value = rawContent.value
+}
+
 watch(mode, async (newMode) => {
+  if (newMode === "edit") {
+    void checkFreshness()
+    return
+  }
+
   const hasUserFinishedToEdit =
     newMode === "read" && rawContent.value !== initialRawContent.value
 
@@ -141,28 +210,35 @@ watch(mode, async (newMode) => {
   }
   if (!path.value) {
     console.warn("no path found for this file")
-
     return
   }
 
-  const editedSha = (await getEditedSha()) ?? sha.value
-  const newSha = await updateFile({
-    content: rawContent.value,
-    path: path.value,
-    sha: editedSha
-  })
-
-  if (!newSha) {
-    console.warn("no new SHA found for this file")
-
+  await checkFreshness()
+  if (freshnessStatus.value === "outdated") {
+    conflictOpen.value = true
     return
   }
 
-  await saveCacheNote(encodeUTF8ToBase64(rawContent.value), {
-    editedSha: newSha
-  })
-  initialRawContent.value = rawContent.value
+  await performSave()
 })
+
+const onConflictDiscard = async () => {
+  const newRaw = await pullLatest()
+  if (newRaw !== null) {
+    rawContent.value = newRaw
+    initialRawContent.value = newRaw
+  }
+}
+
+const onConflictOverwrite = async () => {
+  if (latestSha.value) {
+    await performSave(latestSha.value)
+  }
+}
+
+const onConflictCancel = () => {
+  if (mode.value === "read") toggleMode()
+}
 </script>
 
 <template>
@@ -190,13 +266,19 @@ watch(mode, async (newMode) => {
       </div>
     </a>
     <section class="text-content">
-      <button
-        v-if="isMarkdown"
-        class="action button is-text is-light"
-        :class="{ 'is-link': mode === 'edit' }"
-        :style="mode === 'edit' ? 'color: var(--color-primary)' : ''"
-        @click="toggleMode"
-      >
+      <div class="action-bar">
+        <note-freshness-badge
+          :status="freshnessStatus"
+          :last-checked-at="lastCheckedAt"
+          @click="checkFreshness"
+        />
+        <button
+          v-if="isMarkdown"
+          class="action button is-text is-light"
+          :class="{ 'is-link': mode === 'edit' }"
+          :style="mode === 'edit' ? 'color: var(--color-primary)' : ''"
+          @click="toggleMode"
+        >
         <svg
           v-if="mode === 'read'"
           xmlns="http://www.w3.org/2000/svg"
@@ -240,6 +322,7 @@ watch(mode, async (newMode) => {
           <path d="M14 4l0 4l-6 0l0 -4" />
         </svg>
       </button>
+      </div>
       <div v-if="mode === 'edit' && isMarkdown" class="edit">
         <edit-note v-model="rawContent" />
       </div>
@@ -250,6 +333,12 @@ watch(mode, async (newMode) => {
       ></div>
     </section>
     <linked-notes v-if="hasBacklinks && content" :sha="sha" />
+    <note-conflict-modal
+      v-model:open="conflictOpen"
+      @discard="onConflictDiscard"
+      @overwrite="onConflictOverwrite"
+      @cancel="onConflictCancel"
+    />
   </div>
 </template>
 
@@ -296,14 +385,22 @@ $border-color: rgba(18, 19, 58, 0.2);
   flex: 1;
   scrollbar-width: none;
 
-  div {
+  > .edit,
+  > .note-content {
     height: 100%;
   }
 }
 
+.action-bar {
+  display: flex;
+  align-items: center;
+  justify-content: flex-end;
+  gap: 0.25rem;
+  margin: 0.2rem 0;
+}
+
 .action {
-  float: right;
-  margin: 0.2rem;
+  margin: 0;
 
   img {
     vertical-align: bottom;
diff --git a/src/hooks/useNoteFreshness.hook.ts b/src/hooks/useNoteFreshness.hook.ts
new file mode 100644
index 0000000..c1968c4
--- /dev/null
+++ b/src/hooks/useNoteFreshness.hook.ts
@@ -0,0 +1,106 @@
+import { computed, Ref, ref } from "vue"
+
+import { useGitHubContent } from "@/hooks/useGitHubContent.hook"
+import { markdownBuilder } from "@/hooks/useMarkdown.hook"
+import { prepareNoteCache } from "@/modules/note/cache/prepareNoteCache"
+import { queryFileContent } from "@/modules/repo/services/repo"
+import { useUserRepoStore } from "@/modules/repo/store/userRepo.store"
+
+export type FreshnessStatus =
+  | "unknown"
+  | "checking"
+  | "verified"
+  | "stale-known"
+  | "outdated"
+  | "offline"
+
+const STALE_AFTER_MS = 2 * 60 * 1000
+
+export const useNoteFreshness = ({
+  user,
+  repo,
+  sha,
+  path,
+  getEditedSha
+}: {
+  user: string
+  repo: string
+  sha: Ref<string>
+  path: Ref<string | undefined>
+  getEditedSha: () => Promise<string | null>
+}) => {
+  const store = useUserRepoStore()
+  const { fetchLatestSha } = useGitHubContent({ user, repo })
+
+  const rawStatus = ref<FreshnessStatus>("unknown")
+  const lastCheckedAt = ref<Date | null>(null)
+  const latestSha = ref<string | null>(null)
+  const tick = ref(0)
+  let staleTimer: ReturnType<typeof setTimeout> | null = null
+
+  const status = computed<FreshnessStatus>(() => {
+    void tick.value
+    if (rawStatus.value !== "verified") return rawStatus.value
+    if (!lastCheckedAt.value) return rawStatus.value
+    const age = Date.now() - lastCheckedAt.value.getTime()
+    return age > STALE_AFTER_MS ? "stale-known" : "verified"
+  })
+
+  const armStaleTimer = () => {
+    if (staleTimer) clearTimeout(staleTimer)
+    staleTimer = setTimeout(() => {
+      tick.value++
+    }, STALE_AFTER_MS + 100)
+  }
+
+  const expectedSha = async () => (await getEditedSha()) ?? sha.value
+
+  const check = async () => {
+    if (!path.value) return
+    rawStatus.value = "checking"
+    const remoteSha = await fetchLatestSha(path.value)
+    if (remoteSha === null) {
+      rawStatus.value = "offline"
+      return
+    }
+    latestSha.value = remoteSha
+    lastCheckedAt.value = new Date()
+    const local = await expectedSha()
+    rawStatus.value = remoteSha === local ? "verified" : "outdated"
+    armStaleTimer()
+  }
+
+  const pullLatest = async (): Promise<string | null> => {
+    if (!path.value) return null
+    const remoteSha = latestSha.value ?? (await fetchLatestSha(path.value))
+    if (!remoteSha) {
+      rawStatus.value = "offline"
+      return null
+    }
+    const fileContent = await queryFileContent(user, repo, remoteSha)
+    if (!fileContent) {
+      rawStatus.value = "offline"
+      return null
+    }
+    const { saveCacheNote } = prepareNoteCache(sha.value, path.value)
+    await saveCacheNote(fileContent, {
+      editedSha: remoteSha,
+      path: path.value
+    })
+    store.addFile({ path: path.value, sha: remoteSha })
+    latestSha.value = remoteSha
+    lastCheckedAt.value = new Date()
+    rawStatus.value = "verified"
+    armStaleTimer()
+    const { getRawContent } = markdownBuilder(sha.value)
+    return getRawContent(fileContent)
+  }
+
+  return {
+    status,
+    lastCheckedAt,
+    latestSha,
+    check,
+    pullLatest
+  }
+}