Browser compatibility

Server-sent events is supported natively by all modern browsers.

You can safely use the EventSource interface without having to add any extra dependencies to your front-end code bundle.

Nevertheless, should you need to support older browsers, some polyfills are listed below.

Can I Use…

Data on support for the eventsource feature across the major browsers from caniuse.com

Can I use… Server-sent events

Polyfills

`lukas-reining/eventsource`

EventSource implementation that is fully compliant with the WHATWG Server-Sent Events specification but takes more arguments.

Usable in browser and Node.js environments (uses the Fetch API)
TypeScript types
Custom HTTP method
Custom headers
Custom retry time
Automatic logging

`joshmossas/event-source-plus`

A more configurable EventSource implementation that runs in browsers, NodeJS, and workers.

Usable in browser, Node.js and worker environments (uses the Fetch API)
TypeScript types
Custom HTTP method
Custom headers
Custom URL search parameters
Custom retry time and strategies

`mpetazzoni/sse.js`

A flexible EventSource replacement for JavaScript designed to consume Server-Sent Events (SSE) streams with more control and options than the standard EventSource.

TypeScript types
Custom HTTP method
Custom headers
Control when request is initiated

`Azure/fetch-event-source`

Or its fork: ai-zen/node-fetch-event-source

A better API for making Event Source requests, with all the features of fetch()

TypeScript types
Custom HTTP method
Custom headers
Custom retry time and strategies

`Yaffle/EventSource`

A polyfill for EventSource.

Custom headers
Custom Last-Event-ID query parameter name

`amvtek/EventSource`

Provides a polyfill to support EventSource in browsers where it is not available.

Custom headers
Custom URL search parameters
Automatic logging