Why use IndexedDB instead of LocalStorage for offline apps?

IndexedDB supports much larger data volumes (often 1GB+), handles complex queries asynchronously, and does not block the UI thread, making it the industry standard for robust offline-first applications.

How does this skill handle data conflicts between devices?

It provides implementation patterns for three major strategies: Last-Write-Wins (LWW) for simplicity, Field-Level Merges to preserve independent changes, and Version Vectors for complex concurrent modifications.

What are 'tombstones' and why are they required?

Tombstones are soft-delete markers (_deletedAt). They are essential in offline-first systems because hard-deleting a record locally would prevent the server and other clients from knowing the record should be removed, often leading to data 'resurrecting' during sync.

Does this skill work with all modern browsers?

Yes, while features like the Background Sync API are browser-specific, the core patterns use standard IndexedDB and network event listeners that work across all modern browsers, including Safari (with specific handling for its 7-day storage cap).

Offline-First PWA Patterns

Name: Offline-First PWA Patterns
Author: agents-inc

byagents-inc

0•

Mobile Development

Implements robust local-first architectures using IndexedDB, sync queues, and optimistic UI patterns for resilient web applications.

The web-pwa-offline-first skill provides a comprehensive framework for building Progressive Web Apps that treat network connectivity as an enhancement rather than a requirement. It establishes IndexedDB as the single source of truth and implements sophisticated synchronization logic including sync metadata, mutation queues with exponential backoff, and soft-delete tombstones. By following these patterns, developers can create applications that offer instant responsiveness and seamless data persistence, even in environments with intermittent or zero internet access.

主な機能

01IndexedDB-backed local-first data architecture using Dexie.js or idb

02Reliable sync queues with exponential backoff and jitter for background processing

03Optimistic UI patterns with built-in rollback support for instant user feedback

04Advanced conflict resolution strategies including Last-Write-Wins and Field-Level Merge

05Soft delete (tombstone) implementation to prevent data resurrection across devices

060 GitHub stars

ユースケース

01Developing field service applications for users in remote areas with poor connectivity

02Building high-performance productivity or note-taking apps requiring instant data persistence

03Creating PWAs that need to maintain state and functionality across browser refreshes and offline periods

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add agents-inc/skills web-pwa-offline-first

For use in Claude.ai and ChatGPT

Download Skill