Capital.com API GET /api/v1/session/encryptionKey
Fetch the key and timestamp used to send the API key password in encrypted form when starting a session. Only the encrypted login route needs it.
Risk warning: CFDs and spread bets are complex instruments and come with a high risk of losing money rapidly due to leverage. You can lose money on these products, and each provider publishes its own loss figure under FCA rules. You should consider whether you understand how they work and whether you can afford to take the high risk of losing your money. Automated and API trading can amplify losses through bugs, connectivity failures and runaway orders.
Read on Capital.com's own reference at open-api.capital.com on 12 Oct 2026: method, path, the header and the example response. The reference does not flag the header as required. Its authentication section says the API key goes in X-CAP-API-KEY, which is why it is recorded as required.
Parameters
No parameters recorded beyond authentication.
Authentication headers
| Name | Type | Description |
|---|---|---|
| X-CAP-API-KEYrequired | string | Your API key, generated in the platform settings. Placeholder only: never paste a real key into this site. |
Request
Written from the method, path and parameters recorded on this page, against the demo host. Not executed against a live or demo account. Credentials are read from environment variables on your own machine and are never entered on this site. The request builder writes these same snippets, from the same record.
Python
# Set CAPITAL_API_KEY as an environment variable first. Never paste real values into code.
import os
import requests
BASE_URL = "https://demo-api-capital.backend-capital.com" # the demo host
headers = {
"X-CAP-API-KEY": os.environ["CAPITAL_API_KEY"],
}
resp = requests.get(BASE_URL + "/api/v1/session/encryptionKey", headers=headers, timeout=10)
resp.raise_for_status()
print(resp.json())JavaScript
// Set CAPITAL_API_KEY as an environment variable first. Never paste real values into code.
// Run as a module, for example a .mjs file, on a Node version that has fetch built in.
const BASE_URL = "https://demo-api-capital.backend-capital.com"; // the demo host
const res = await fetch(BASE_URL + "/api/v1/session/encryptionKey", {
method: "GET",
headers: {
"X-CAP-API-KEY": process.env.CAPITAL_API_KEY,
},
});
if (!res.ok) throw new Error(`HTTP ${res.status}`);
console.log(await res.json());curl
# Set CAPITAL_API_KEY as an environment variable first. Never paste real values into code. curl -X GET "https://demo-api-capital.backend-capital.com/api/v1/session/encryptionKey" \ -H "X-CAP-API-KEY: $CAPITAL_API_KEY"
Response
A mock response. The values are invented, so check field names against the official reference.
{
"_mock": true,
"encryptionKey": "MOCK-BASE64-KEY",
"timeStamp": 1789718400000
}Limits that apply at Capital.com
| Limit | Value | Scope | Source |
|---|---|---|---|
| Headline limit | 10/s per user | user | open-api.capital.comchecked |
Capital.com API errors you may meet
- error.account.limit.reachedHTTP 400. The demo account's balance cap has been reached, so it cannot be topped up further.
- error.invalid.accountHTTP 400. The account selected for a demo balance top up is not valid.
- error.invalid.accountIdHTTP 400. The account id sent when switching the active account is not valid.
- error.invalid.amountHTTP 400. The amount in a demo balance top up request is not valid.
- error.invalid.detailsHTTP 401. Invalid credentials on session creation.
- error.invalid.fromHTTP 400. The from parameter of an activity history request is not valid.
All Capital.com API error codes, including 18 more not listed here.