Dev
Mock Server-Sent Event Generator
Server-Sent Events have a specific wire format that client parsers must handle exactly: each event is a block of colon-delimited field lines terminated by a blank line. The blank line is not optional — it is what tells the client to dispatch the event. Writing a correct multi-event SSE stream by hand for a test is fiddly and error-prone. This tool generates one for you. Choose how many events you want, from 1 to 10. Each event includes an id (an incrementing integer starting from a random offset), an event field (one of message, update, progress, or notification), and a data field containing a JSON object with status, value, and ref keys. The blank line separator between events is included in the output. Copy the stream into a test for your SSE client parser, or serve it verbatim from a mock endpoint with Content-Type: text/event-stream. Because the format is correct down to the blank line, the stream exercises the full client parsing path — not just individual field handling.
How to use
- Choose your options above
- Click Generate
- Copy your result
Detailed instructions
- Choose how many events you want.
- Click Generate to produce an SSE stream.
- Copy it into your test or mock endpoint.
- Use it to exercise your SSE client.
Use Cases
- •Testing an SSE client parser
- •Building a mock streaming endpoint
- •Learning the Server-Sent Events format
- •Seeding sample real-time data
- •Demoing a live-update feature
Tips
- →Each event ends with a blank line.
- →SSE is one-way, server to client.
- →The data field here carries JSON.
- →Test parsing before wiring a live stream.
FAQ
what are Server-Sent Events
Server-Sent Events are a standard for a server to push updates to a browser over one long-lived HTTP connection. Unlike WebSockets, they are one-way and text-based, with a simple format of id, event, and data fields, making them ideal for live feeds.
why do events have a blank line between them
The blank line separates one event from the next and signals that an event is complete. SSE clients rely on it to know when to dispatch an event, so the format requires a blank line between each event block.
how is SSE different from WebSockets
SSE is one-way — server to client — and runs over plain HTTP with automatic reconnection, which makes it simple for live updates like notifications or progress. WebSockets are two-way and better suited to interactive, bidirectional communication.
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