IndexedDB Storage vs Dexie.js

Comparing LocalMode's built-in IndexedDB storage with the Dexie.js adapter for VectorDB persistence.

Overview

This comparison examines the key differences between IndexedDBStorage (built-in) (https://localmode.dev/docs/core/storage) and DexieStorage (@localmode/dexie) (https://localmode.dev/docs/dexie) for building AI-powered applications. Both approaches have their strengths - the right choice depends on your specific requirements around privacy, cost, performance, and target platforms.

Understanding these trade-offs is essential for architects and developers evaluating local-first AI versus alternative approaches. The comparison below covers 8 dimensions, from runtime characteristics to model quality and developer experience.

Feature-by-Feature Comparison

Verdict

Start with IndexedDBStorage (built-in, zero dependencies). Switch to DexieStorage when you need schema versioning across app updates, when you want Dexie's query API for non-vector data alongside your VectorDB, or when you're already using Dexie in your application. Both implement the same Storage interface, so switching is a one-line change. For most LocalMode applications focused on vector search, the built-in storage is sufficient.

Summary

When evaluating IndexedDBStorage (built-in) against DexieStorage (@localmode/dexie), consider your primary constraints:

• Privacy requirements - If user data must never leave the device, solutions that process everything locally have an inherent architectural advantage.
• Cost at scale - Per-request pricing models become expensive as user counts grow. Local inference shifts the cost to a one-time model download per user.
• Target platforms - Browser-based solutions work on any device with a modern browser. Desktop and server-based solutions may require additional installation steps.
• Model quality needs - For tasks where the absolute highest quality matters (complex multi-step reasoning, creative writing), larger server-side or cloud models still have an edge. For the majority of practical tasks (embeddings, classification, summarization, simple generation), the quality gap has narrowed significantly.
• Offline requirements - Applications that must work without internet need local inference. Cloud-dependent solutions fail when connectivity drops.

Making the Decision

For many teams, the answer is not either/or. A hybrid architecture uses local inference for high-volume, low-complexity tasks (embeddings, classification, NER, simple generation) at zero marginal cost, and routes the small percentage of requests that genuinely need frontier-quality reasoning to a cloud provider. A plain try/catch makes this pattern straightforward to implement:

import { streamText } from '@localmode/core';

// Try the local model first (free, private, fast)
// Fall back to a cloud call only if local inference fails
async function generate(prompt: string) {
  try {
    return await streamText({ model: localModel, prompt });
  } catch (error) {
    console.warn('Local inference failed, escalating to cloud:', error);
    return await callCloudProvider(prompt);
  }
}

This approach gives you the best of both worlds: the privacy and cost benefits of local inference for the 90% of requests that don't need frontier quality, and the option to escalate to cloud APIs for the remaining 10%.

Related Pages

• Text Embeddings - task guide
• Dexie Vs Idb Vs Localforage - comparison guide

Methodology

Feature claims about LocalMode's IndexedDBStorage and DexieStorage were verified directly against the source code (packages/core/src/storage/indexeddb.ts and packages/dexie/src/storage.ts) and the built dist artifacts. The @localmode/dexie adapter bundle size (~3.4KB ESM) was measured from the compiled dist/index.js. Dexie.js bundle sizes (minified ~95KB, gzip ~31KB) were retrieved from the Bundlephobia API for dexie@4.3.0, which is the version pinned in packages/dexie/package.json. Performance comparisons are qualitative; no specific benchmark figures are claimed. Verify current sizes with each tool's registry page before making decisions.

Sources

• LocalMode @localmode/dexie source - packages/dexie/src/storage.ts
• LocalMode IndexedDBStorage source - packages/core/src/storage/indexeddb.ts
• Bundlephobia - dexie@4.3.0 bundle size (~95KB minified / ~31KB gzip)
• dexie on npm - version history and latest release
• Dexie.js GitHub releases - v4.4.2 (latest as of March 2026)
• MDN - IndexedDB API
• Can I Use - IndexedDB (~96% global browser support)