Fireproof Closet

Cache your Firebase Storage data to the Fireproof Closet. When you use the FireproofImage image provider, your image will be loaded instantly from the cache, or it will be downloaded and cached for future display.


The Fireproof Closet cache is persistent, so users can close and re-open the app and not have to wait for images to download again.

In-Memory Speed

Images displayed with the FireproofImage() provider are kept in the hot memory ImageCache for instant loading.

How it Works

Fireproof Closet is a combination of a custom ImageProvider called FireproofImage which is capable of acquiring and caching images from Firebase Storage, and the Hive database to store and manage the data in persistence. Images are loaded into the hot memory ImageCache when displayed with the FireproofImage() provider, or ahead of time with pre-caching by using FireproofCloset.downloadAndCache(context, storageRef);.

Cross Platform

  • Hive is a cross-platform database that has fast speeds on all Flutter platforms.
  • The rest of the Fireproof Closet system is written in Dart which is inherently cross-platform

Speed Example

Loading images from persistent cache vs downloading from Firebase Storage on iOS.

First cache read after the database is initialized may be slower. Cache reads below are for subsequent reads.

After reading from persistent cache, the image is stored in hot memory for instant loading. The following reflects speed improvements compared to Firebase Storage downloading.

70 KB Image

  • Not found in cache, downloading from Firebase Storage

    • Cache stage duration: ~45ms
    • Firebase storage stage duration: 338ms
  • Loaded from cache

    • Cache stage duration: ~12ms
    • Firebase storage stage duration: 0ms

7 MB Image

  • Not found in cache, downloading from Firebase Storage

    • Cache stage duration: ~45ms
    • Firebase storage stage duration: 913ms
  • Loaded from cache

    • Cache stage duration: ~60ms
    • Firebase storage stage duration: 0ms

Future Changes

In the future, Hive will be replaced with Isar which is a cross-platform database that uses native code for each platform. However, Web does not currently work properly.

  • Isar loads large images into memory from persistent storage approximately 3x faster (7 MB in ~20ms) but the difference is negligible on smaller images under 1 MB.
  • This upgrade should be a non-breaking change since the API will remain identical, but with a higher speed database behind the scenes.


Initialize Fireproof Closet at app startup

import 'package:fireproof_closet/fireproof_closet.dart';

void main() async {

  // Firebase: Initialize Firebase
  await Firebase.initializeApp(
    options: DefaultFirebaseOptions.currentPlatform,

  // Initialize Firebase Storage Image Caching
  await FireproofCloset.initialize();
  // ...

Display An Image

FireproofImage is an image provider that can be provided to an Image widget, or any widget that takes an image provider.

import 'package:firebase_storage/firebase_storage.dart';
import 'package:fireproof_closet/fireproof_closet.dart';

class TestWidget extends StatelessWidget {
  const TestWidget({Key? key}) : super(key: key);

  Widget build(BuildContext context) {
    return Image(
      image: FireproofImage(
        storageRef: FirebaseStorage.instance
                .child("full/path/to/image.jpg"), // Required, the full relative path to the image in Firebase Storage
        breakCache: true, // Optional, defaults to false, will force a fresh download and evict the image from memory
        cacheDuration: const Duration(minutes: 5), // Optional, defaults to 365 days
        cache: false, // Optional, defaults to true. If false, will not save the image to persistent cache

Precache Images (or files)

Download images before they need to be shown to improve the user experience.

(This also works with any file, and not just images.)

This is helpful for long scrolling ListView.builder() type widgets, where you do not want to wait for each image to download from Firebase Storage as it is scrolled into view. Load it from the cache in milliseconds instead.

Optionally, await these downloads.


Precache a ton of images at a time

// A list of Firebase Storage References
List<Reference> files = [

// Cache them all at once in a loop
// If context is null, images will only be downloaded to persistence and not loaded into hot memory [ImageCache]
for (var file in files) {
  FireproofCloset.downloadAndCache(storageRef, context: context);

Helpful Utilities

Clear the cache

Delete all items from the cache



Example Output

flutter: Number of cached items: 1
flutter: Total cache size 0.0689 MB


Example Output

flutter: =====================
flutter: All cached items:
flutter: 0 CachedData: fullPath: full/path/to/image.jpg, size: 68.87 kb, created: 2022-11-20 20:19:04.624, expires: 2022-11-20 20:24:04.624
flutter: End of cached items.
flutter: =====================