Quickstart

1. Create a key from your dashboard. It is shown once, so copy it straight into an environment variable.
2. Send it as a bearer token on every request.
3. Read the JSON response.

Request

curl https://sentimentindex.io/api/v1/fear-greed \
  -H "Authorization: Bearer $SENTIMENT_API_KEY"

Response

{
  "as_of": "2026-08-29",
  "current": 54,
  "zone": "Neutral",
  "previous_close": 51,
  "indicators": { "market_momentum": 52.4, "...": null },
  "plan": "free"
}

Python

import os, requests

r = requests.get(
    "https://sentimentindex.io/api/v1/fear-greed",
    headers={"Authorization": f"Bearer {os.environ['SENTIMENT_API_KEY']}"},
    timeout=10,
)
r.raise_for_status()
print(r.json()["current"])

JavaScript

const res = await fetch("https://sentimentindex.io/api/v1/fear-greed", {
  headers: { Authorization: `Bearer ${process.env.SENTIMENT_API_KEY}` },
});
if (!res.ok) throw new Error(await res.text());
const { current, zone } = await res.json();

Authentication

Pass your key in the Authorization header using the Bearer scheme. Keys begin with sk_live_.

Authorization: Bearer sk_live_xxxxxxxxxxxxxxxxxxxx

There is no query-string parameter for the key, deliberately: URLs are written to server logs, browser history and Referer headers, and a key that reaches any of those is compromised.

Rate limits

Limits are applied per key on a rolling hourly window. Every response carries the current state:

X-RateLimit-Limit: 60
X-RateLimit-Remaining: 57

Exceeding the limit returns 429 with a Retry-After header in seconds. Back off for that long rather than retrying immediately.

Errors

Errors return the appropriate status with a JSON body of the form { "error": "..." }.

Endpoints

Endpoints marked live are available now. The rest are documented ahead of release and are not yet callable.

Key security

• Store keys in environment variables, never in source control. If a key reaches a public repository, revoke it immediately.
• Use one key per application. A leak then costs you one revocation rather than every integration you run.
• Rotate on staff changes and whenever a key may have been exposed. Create the replacement, deploy it, then revoke the old one for zero downtime.
• We cannot recover a key. Only a hash is stored, so support cannot read one back to you. Rotation is always the answer.

Manage all of this from your API keys dashboard.