HTTP 503 in broker APIs: what it means, broker by broker
3 decoded error codes from 2 brokers and platforms return this status, and one general record gives the standard's meaning: 4 records on this page. The count is of records whose recorded HTTP status is 503. A search for the number 503 also finds records that only mention it in their code or meaning, so the error lookup can show more.
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.
What the status means in general
HTTP 503 is Service Unavailable. The server cannot handle the request for now because of a temporary overload or scheduled maintenance, which is likely to ease after some delay. The server may send a Retry-After header to suggest how long to wait.
Maintenance windows, outages and overload show up as 503. Whether a market is open is a different matter: an API can be up while a market is closed, and that is normally reported through the API's own code.
Honour Retry-After if the reply carries it, otherwise wait and retry with growing gaps. Check the provider's status page. For an order request, read open orders and positions before sending it again.
The first paragraph is the standard's meaning in this site's words, with its source. The rest is this site's own explanation and describes no particular broker. HTTP 503 Service Unavailable on its own page.
The status alone is only the category. The code or message in the body of the reply is what tells you the cause, and that differs from one API to the next.
The decoded errors that return it
In order of broker name, then code. Each row links to the full meaning and the fix.
Interactive Brokers
| Code | Meaning, first sentence | Source |
|---|---|---|
| 503 on order reply | On the Web API, Interactive Brokers says an order reply must be confirmed straight after it is received and before any further order is sent. | interactivebrokers.comchecked |
| 503 Service Unavailable | On the Web API, the reference for submitting an order lists 503 Service Unavailable. | interactivebrokers.comchecked |
Saxo OpenAPI
| Code | Meaning, first sentence | Source |
|---|---|---|
| HTTP 503 | The service is temporarily unavailable. | developer.saxochecked |
Brokers and platforms not listed here have no decoded error recorded with this status. That describes this dataset, not their APIs.