Glossary A–ZLetter W
Webhook
A webhook is a notification that a system sends automatically, when a particular event occurs, to a web address of another system registered in advance, instead of the other system having to ask repeatedly.
It is also described as an HTTP callback.
In screen networks, webhooks trigger a message, for example, when a player goes offline, a campaign has been approved or new content has been uploaded. Conversely, an external system can use a webhook to tell the signage system that a price has changed or an emergency has occurred, after which different content appears immediately. The message usually contains data in JSON format.
Because any reachable address can receive requests, webhooks must be secured: with encrypted connections and a signature or shared secret by which the recipient recognises genuine messages. Operators should bear in mind that a message can be lost or arrive twice; important processes need retries and a check for duplicates. A webhook therefore does not replace regular checks of the status.