diff --git a/src/routes/_database/cleanup.js b/src/routes/_database/cleanup.js
index 04c0f815..787e7548 100644
--- a/src/routes/_database/cleanup.js
+++ b/src/routes/_database/cleanup.js
@@ -16,10 +16,9 @@ import { deleteAll } from './utils'
 import { createPinnedStatusKeyRange, createThreadKeyRange } from './keys'
 import { getKnownInstances } from './knownInstances'
 import noop from 'lodash-es/noop'
+import { CLEANUP_DELAY, CLEANUP_TIME_AGO } from '../_static/database'
 
 const BATCH_SIZE = 20
-export const TIME_AGO = 5 * 24 * 60 * 60 * 1000 // five days ago
-const DELAY = 5 * 60 * 1000 // five minutes
 
 function batchedGetAll (callGetAll, callback) {
   function nextBatch () {
@@ -124,7 +123,7 @@ export async function cleanup (instanceName) {
       pinnedStatusesStore
     ] = stores
 
-    const cutoff = Date.now() - TIME_AGO
+    const cutoff = Date.now() - CLEANUP_TIME_AGO
 
     cleanupStatuses(statusesStore, statusTimelinesStore, threadsStore, cutoff)
     cleanupNotifications(notificationsStore, notificationTimelinesStore, cutoff)
@@ -148,4 +147,4 @@ async function scheduledCleanup () {
 }
 
 // we have unit tests that test indexedDB; we don't want this thing to run forever
-export const scheduleCleanup = process.browser ? debounce(scheduledCleanup, DELAY) : noop
+export const scheduleCleanup = process.browser ? debounce(scheduledCleanup, CLEANUP_DELAY) : noop
diff --git a/src/routes/_static/database.js b/src/routes/_static/database.js
new file mode 100644
index 00000000..ee302bfd
--- /dev/null
+++ b/src/routes/_static/database.js
@@ -0,0 +1,2 @@
+export const CLEANUP_TIME_AGO = 5 * 24 * 60 * 60 * 1000 // five days ago
+export const CLEANUP_DELAY = 5 * 60 * 1000 // five minutes
diff --git a/src/routes/_store/mixins/instanceMixins.js b/src/routes/_store/mixins/instanceMixins.js
index 8a61c384..e07da488 100644
--- a/src/routes/_store/mixins/instanceMixins.js
+++ b/src/routes/_store/mixins/instanceMixins.js
@@ -4,7 +4,11 @@ export function instanceMixins (Store) {
   Store.prototype.setComposeData = function (realm, obj) {
     const { composeData, currentInstance } = this.get()
     const instanceNameData = composeData[currentInstance] = composeData[currentInstance] || {}
-    instanceNameData[realm] = Object.assign(instanceNameData[realm] || {}, obj)
+    instanceNameData[realm] = Object.assign(
+      instanceNameData[realm] || {},
+      { ts: Date.now() },
+      obj
+    )
     this.set({ composeData })
   }
 
diff --git a/src/routes/_store/observers/cleanup.js b/src/routes/_store/observers/cleanup.js
new file mode 100644
index 00000000..d2e8279a
--- /dev/null
+++ b/src/routes/_store/observers/cleanup.js
@@ -0,0 +1,31 @@
+import { store } from '../store'
+import { scheduleIdleTask } from '../../_utils/scheduleIdleTask'
+import { CLEANUP_DELAY, CLEANUP_TIME_AGO } from '../../_static/database'
+
+function doCleanup () {
+  // Periodically clean up drafts in localStorage, so they don't grow without bound.
+  // Only do this for replies, so not for the home timeline or the compose modal.
+  const now = Date.now()
+  let changeCount = 0
+  const { composeData } = store.get()
+  for (const instanceComposeData of Object.values(composeData)) {
+    for (const [realm, timelineComposeData] of Object.entries(instanceComposeData)) {
+      if (realm === 'home' || realm === 'dialog') {
+        continue
+      }
+      const ts = timelineComposeData.ts || 0 // if no timestamp set, just assume it's very old (migration behavior)
+      if (now - ts > CLEANUP_TIME_AGO) {
+        delete instanceComposeData[realm]
+        changeCount++
+      }
+    }
+  }
+  console.log('deleted', changeCount, 'old drafts')
+  if (changeCount) {
+    store.set({ composeData })
+  }
+}
+
+export function cleanup () {
+  setInterval(() => scheduleIdleTask(doCleanup), CLEANUP_DELAY)
+}
diff --git a/src/routes/_store/observers/loggedInObservers.js b/src/routes/_store/observers/loggedInObservers.js
index 35261f59..0f8d4a82 100644
--- a/src/routes/_store/observers/loggedInObservers.js
+++ b/src/routes/_store/observers/loggedInObservers.js
@@ -4,6 +4,7 @@ import { notificationObservers } from './notificationObservers'
 import { autosuggestObservers } from './autosuggestObservers'
 import { notificationPermissionObservers } from './notificationPermissionObservers'
 import { customScrollbarObservers } from './customScrollbarObservers'
+import { cleanup } from './cleanup'
 
 // These observers can be lazy-loaded when the user is actually logged in.
 // Prevents circular dependencies and reduces the size of main.js
@@ -14,4 +15,5 @@ export default function loggedInObservers () {
   autosuggestObservers()
   notificationPermissionObservers()
   customScrollbarObservers()
+  cleanup()
 }
diff --git a/tests/unit/test-database.js b/tests/unit/test-database.js
index 17c8a2b0..4a515372 100644
--- a/tests/unit/test-database.js
+++ b/tests/unit/test-database.js
@@ -10,7 +10,8 @@ import {
   TIMESTAMP, ACCOUNT_ID, STATUS_ID, REBLOG_ID, USERNAME_LOWERCASE,
   CURRENT_TIME, DB_VERSION_CURRENT, DB_VERSION_SEARCH_ACCOUNTS, DB_VERSION_SNOWFLAKE_IDS
 } from '../../src/routes/_database/constants'
-import { cleanup, TIME_AGO } from '../../src/routes/_database/cleanup'
+import { cleanup } from '../../src/routes/_database/cleanup'
+import { CLEANUP_TIME_AGO } from '../../src/routes/_static/database'
 
 const INSTANCE_NAME = 'localhost:3000'
 
@@ -91,7 +92,7 @@ describe('test-database.js', function () {
       // set a timestamp based on the *current* date when the status is inserted,
       // not the date that the status was composed.
 
-      const longAgo = Date.now() - (TIME_AGO * 2)
+      const longAgo = Date.now() - (CLEANUP_TIME_AGO * 2)
 
       const oldStatus = {
         id: '1',