# jcubic/sysend

Web application synchronization between different tabs

Repository: https://github.com/jcubic/sysend
Canonical: https://ross.abutalabs.com/products/sysend
Language: JavaScript
License: MIT
License Family: permissive
Topics: callback, notifications, events, browser, tabs, javascript, proxy, messages, pubsub, communication, synchronization, cross-tab, rpc
Last push: 2026-03-20T00:22:02+00:00

## Health v2 (maintenance only)
Score: 56/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 73, release rhythm 8, longevity 100
- inputs: {"age_days": 4465, "days_push": 167, "days_rel": 688, "gap_med": null, "n_releases_24m": 1}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1163, forks 73 (observed 2026-08-28T04:03:49.733136+00:00)

## What it is
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
- artifact type: library
- maturity: active
- function: websocket, message-queue, middleware
- domain: web-development, frontend, browser-extensions
- platform: browser
- tags: cross-tab-communication, localstorage, broadcastchannel, pubsub, cross-origin, inter-tab-messaging, zero-dependency, javascript

## Member repositories
- jcubic/sysend (main) score 56

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:03:49.733136+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T06:31:34.129868+00:00, confidence not recorded.
  - readme: https://github.com/jcubic/sysend (fetched 2026-08-28T04:03:49.733136+00:00, sha 507905070aa8)
- Data as of 2026-08-30T08:39:29.467469+00:00.