diff --git a/src/index.ts b/src/index.ts
index 4163a69..1682e70 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -5,12 +5,17 @@ function shouldResumeField(field: HTMLInputElement | HTMLTextAreaElement): boole
   return !!field.id && field.value !== field.defaultValue && field.form !== submittedForm
 }
 
-type PersistOptions = {selector?: string; keyPrefix?: string}
+type PersistOptions = {
+  selector?: string
+  keyPrefix?: string
+  storage?: Pick<Storage, 'getItem' | 'setItem'>
+}
 
 // Write all ids and values of the selected fields on the page into sessionStorage.
 export function persistResumableFields(id: string, options?: PersistOptions): void {
   const selector = options?.selector ?? '.js-session-resumable'
   const keyPrefix = options?.keyPrefix ?? 'session-resume:'
+  const storage = options?.storage ?? sessionStorage
   const key = `${keyPrefix}${id}`
   const resumables = []
 
@@ -24,7 +29,7 @@ export function persistResumableFields(id: string, options?: PersistOptions): vo
 
   if (fields.length) {
     try {
-      const previouslyStoredFieldsJson = sessionStorage.getItem(key)
+      const previouslyStoredFieldsJson = storage.getItem(key)
 
       if (previouslyStoredFieldsJson !== null) {
         const previouslyStoredFields: string[][] = JSON.parse(previouslyStoredFieldsJson)
@@ -34,22 +39,23 @@ export function persistResumableFields(id: string, options?: PersistOptions): vo
         fields = fields.concat(fieldsNotReplaced)
       }
 
-      sessionStorage.setItem(key, JSON.stringify(fields))
+      storage.setItem(key, JSON.stringify(fields))
     } catch {
       // Ignore browser private mode error.
     }
   }
 }
 
-type RestoreOptions = {keyPrefix?: string}
+type RestoreOptions = {keyPrefix?: string; storage?: Pick<Storage, 'getItem' | 'setItem' | 'removeItem'>}
 
 export function restoreResumableFields(id: string, options?: RestoreOptions): void {
   const keyPrefix = options?.keyPrefix ?? 'session-resume:'
+  const storage = options?.storage ?? sessionStorage
   const key = `${keyPrefix}${id}`
   let fields
 
   try {
-    fields = sessionStorage.getItem(key)
+    fields = storage.getItem(key)
   } catch {
     // Ignore browser private mode error.
   }
@@ -84,12 +90,12 @@ export function restoreResumableFields(id: string, options?: RestoreOptions): vo
   // they're needed.
   if (storedFieldsNotFound.length === 0) {
     try {
-      sessionStorage.removeItem(key)
+      storage.removeItem(key)
     } catch {
       // Ignore browser private mode error.
     }
   } else {
-    sessionStorage.setItem(key, JSON.stringify(storedFieldsNotFound))
+    storage.setItem(key, JSON.stringify(storedFieldsNotFound))
   }
 
   setTimeout(function () {
diff --git a/test/test.js b/test/test.js
index c093665..1cd6a1a 100644
--- a/test/test.js
+++ b/test/test.js
@@ -14,7 +14,7 @@ describe('session-resume', function () {
   })
 
   describe('restoreResumableFields', function () {
-    it('restores fields values from session storage', function () {
+    it('restores fields values from session storage by default', function () {
       sessionStorage.setItem('session-resume:test-persist', JSON.stringify([['my-first-field', 'test2']]))
       restoreResumableFields('test-persist')
 
@@ -22,6 +22,24 @@ describe('session-resume', function () {
       assert.equal(document.querySelector('#my-second-field').value, 'second-field-value')
     })
 
+    it('uses a Storage object when provided as an option', function () {
+      const fakeStorageBackend = {}
+      const fakeStorage = {
+        setItem(key, value) {
+          fakeStorageBackend[key] = JSON.stringify(value)
+        },
+        getItem(key) {
+          return JSON.parse(fakeStorageBackend[key] || null)
+        }
+      }
+
+      fakeStorage.setItem('session-resume:test-persist', JSON.stringify([['my-first-field', 'test2']]))
+      restoreResumableFields('test-persist', {storage: fakeStorage})
+
+      assert.equal(document.querySelector('#my-first-field').value, 'test2')
+      assert.equal(document.querySelector('#my-second-field').value, 'second-field-value')
+    })
+
     it('leaves unrestored values in session storage', function () {
       sessionStorage.setItem(
         'session-resume:test-persist',
@@ -79,7 +97,7 @@ describe('session-resume', function () {
   })
 
   describe('persistResumableFields', function () {
-    it('persist fields values to session storage', function () {
+    it('persist fields values to session storage by default', function () {
       document.querySelector('#my-first-field').value = 'test1'
       document.querySelector('#my-second-field').value = 'test2'
       persistResumableFields('test-persist')
@@ -90,6 +108,28 @@ describe('session-resume', function () {
       ])
     })
 
+    it('uses a Storage object when provided as an option', function () {
+      document.querySelector('#my-first-field').value = 'test1'
+      document.querySelector('#my-second-field').value = 'test2'
+
+      const fakeStorageBackend = {}
+      const fakeStorage = {
+        setItem(key, value) {
+          fakeStorageBackend[key] = JSON.stringify(value)
+        },
+        getItem(key) {
+          return JSON.parse(fakeStorageBackend[key] || null)
+        }
+      }
+
+      persistResumableFields('test-persist', {storage: fakeStorage})
+
+      assert.deepEqual(JSON.parse(fakeStorage.getItem('session-resume:test-persist')), [
+        ['my-first-field', 'test1'],
+        ['my-second-field', 'test2']
+      ])
+    })
+
     it('holds onto existing values in the store', function () {
       sessionStorage.setItem('session-resume:test-persist', JSON.stringify([['non-existant-field', 'test3']]))
       document.querySelector('#my-first-field').value = 'test1'