jcubic/sysend

Health v2 · maintenance only

Adoption not part of the score

1163 stars · 73 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-30, confidence not recorded

Sysend.js is a small dependency-free JavaScript library that enables message passing and synchronization between web pages open in the same browser, using the HTML5 LocalStorage or BroadcastChannel APIs. It also supports cross-origin communication between different domains and provides a pub/sub-style event system with callbacks and notifications.

Use cases

• synchronize state between browser tabs
• send messages between open pages in the same browser
• cross-domain communication between iframes
• broadcast notifications to all tabs
• implement pub/sub messaging in the browser
• keep login state consistent across tabs
• communicate between tabs of different origins

When to choose

• you need lightweight tab-to-tab messaging without a backend
• you want to sync UI state across multiple open tabs
• you need cross-origin iframe communication with a tiny footprint
• you want a zero-dependency pub/sub layer for browser tabs

When to avoid

• you need server-side or cross-device messaging (use WebSockets or a message queue)
• you require guaranteed message delivery or persistence
• your target browsers block third-party storage (e.g., Safari 7+, Chrome 115+ cross-domain restrictions)
• you need high-throughput or binary data streaming between tabs

Facets

library · maturity active

websocket message-queue middleware web-development frontend browser-extensions browser cross-tab-communication localstorage broadcastchannel pubsub cross-origin inter-tab-messaging zero-dependency javascript

Member repositories

For agents

markdown · JSON · MCP: product_card(name="jcubic/sysend")