How does IndexedDB compare to WebSQL and localStorage?

Question

Shalini Passi · Answer

IndexedDB is the
modern, recommended way to store structured data in the browser. Here's a clear comparison between
IndexedDB,
WebSQL, and 
localStorage, including their features, support, and limitations:
Feature
IndexedDB
WebSQL (Deprecated)
localStorage
Data Size Limit
Hundreds of MBs+
~5–50 MB (varies)
~5–10 MB
Structure Support
Structured objects
Relational only (SQL)
String-only
Async API
Yes (event or promise)
Async but SQL-based
No, it's synchronous
Binary Data Support
Yes (Blobs, Files)
Yes (via base64 hacks)
No
Query Type
Indexed (No SQL)
SQL Queries (Relational)
Key-value only
Performance
Excellent for large data
Moderate
Poor for large data
Multi-store support
Yes (Object Stores)
Tables
No
Transactions
Yes
Yes
No
Browser Support
All modern browsers
Deprecated in all
All
Offline support
Yes
Yes
Yes
1. IndexedDB
Stores structured data (objects, files, blobs).Uses object stores (like tables) and indexes for fast lookups.Asynchronous API (event-based or promise-based via wrappers like
idb).Built for complex, large-scale offline storage.Binary-safe and scalable.Recommended for modern apps that need structured, reliable offline storage.
2. WebSQL (Deprecated)
Uses SQL for querying (like SQLite).Good for relational data, but:
Deprecated by W3C: no new features, limited future supportNot available in some environments (e.g., Firefox, Safari 16+)
Only useful for legacy apps.Avoid using WebSQL in new projects.
3. localStorage
Simple key-value storage (strings only).Synchronous API — blocks the main thread.Good for small settings or flags (theme, token, etc.).
localStorage.setItem("token", "abc123");
const token = localStorage.getItem("token");
Not suitable for storing large data or binary files.
Use Case Summary
Use Case
Recommended Storage
User settings, theme, token
localStorage
Large datasets (e.g., messages, images)
IndexedDB
Offline-first apps (PWA, sync cache)
IndexedDB
Legacy apps using SQL
WebSQL (avoid now)
Saving files/blobs
IndexedDB
Conclusion
Use IndexedDB for anything beyond simple string values.
It is:
ModernAsynchronousStructuredEfficientFully supported

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How does IndexedDB compare to WebSQL and localStorage?

Shalini Passi

Can you answer this question?

1 Answers

1. IndexedDB

2. WebSQL (Deprecated)

3. localStorage

Use Case Summary

Conclusion

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Feature	IndexedDB	WebSQL (Deprecated)	localStorage
Data Size Limit	Hundreds of MBs+	~5–50 MB (varies)	~5–10 MB
Structure Support	Structured objects	Relational only (SQL)	String-only
Async API	Yes (event or promise)	Async but SQL-based	No, it's synchronous
Binary Data Support	Yes (Blobs, Files)	Yes (via base64 hacks)	No
Query Type	Indexed (No SQL)	SQL Queries (Relational)	Key-value only
Performance	Excellent for large data	Moderate	Poor for large data
Multi-store support	Yes (Object Stores)	Tables	No
Transactions	Yes	Yes	No
Browser Support	All modern browsers	Deprecated in all	All
Offline support	Yes	Yes	Yes

Use Case	Recommended Storage
User settings, theme, token	`localStorage`
Large datasets (e.g., messages, images)	`IndexedDB`
Offline-first apps (PWA, sync cache)	`IndexedDB`
Legacy apps using SQL	`WebSQL` (avoid now)
Saving files/blobs	`IndexedDB`