I built a REST API that detects how your users feel in real time

#webdev #javascript #api #opensource

I got tired of not knowing why users were dropping off in my app. Heatmaps show you where people click. Analytics show you when they leave. But nothing tells you how they felt while using it.

So I built SessionMood API — a REST API that scores user mood in real time based on behavioral events.

How it works

You send behavioral events from your frontend:

fetch("https://session-mood-api-production.up.railway.app/v1/sessions/user_123/events", {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    "x-api-key": "YOUR_API_KEY"
  },
  body: JSON.stringify({ type: "click" })
});

Then read the mood at any point:

fetch("https://session-mood-api-production.up.railway.app/v1/sessions/user_123/mood", {
  headers: { "x-api-key": "YOUR_API_KEY" }
})
.then(r => r.json())
.then(console.log);

Response:

{
  "mood": "frustrated",
  "confidence": 0.85,
  "suggested_action": "offer_help",
  "signals": ["rage_click", "high_error_rate"],
  "event_count": 12
}

Supported event types

click — regular click
rage_click — multiple rapid clicks on the same element
scroll — scroll depth (pass value 0-100)
idle — user stopped interacting
page_view — new page loaded
error — JS error or failed request
hover, focus, blur, copy, paste, navigation

The 6 mood states

Mood	Signals
frustrated	rage clicks, errors
engaged	active clicks, deep scrolls
bored	long idle, minimal interaction
confused	repeated actions, back-and-forth
curious	exploratory scrolling, hovering
satisfied	smooth session, positive signals