> For the complete documentation index, see [llms.txt](https://help.security.gallagher.com/knowledge-hub/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.security.gallagher.com/knowledge-hub/products/cc-software/configure/interface-options/api/representational-state-transfer-rest-api/rest-api-what-is-an-api-key.md). # REST API - what is an API key? Understand REST API key contents, request headers, and protection measures. #### What is an API Key? The API key is sent with every request. It **combines the username and password**, so guard it. If the key is stolen and you have no client certificate or IP filtering, an attacker can masquerade as you. A missing or unknown key makes Command Centre raise the alarm **"A REST connection was attempted with an invalid API key"**. In the HTTP header the client prepends `GGL-API-KEY` (with a space) to the key. That prefix is **not** part of the key. Protect the key with **client certificates** and **IP filtering**, both configured on the REST Client item. *** 🔗 **Related** * [REST API - Setting up REST API in Command Center](/knowledge-hub/products/cc-software/configure/interface-options/api/representational-state-transfer-rest-api/rest-api-setting-up-rest-api-in-command-center.md). Where the key is generated. * [REST API - Certificates](/knowledge-hub/products/cc-software/configure/interface-options/api/representational-state-transfer-rest-api/rest-api-certificates.md). The second layer of protection. * [REST API - Troubleshooting a Technology Partner Integration](/knowledge-hub/products/cc-software/configure/interface-options/api/representational-state-transfer-rest-api/rest-api-troubleshooting-a-technology.md). Where the key fits in a partner-integration fault. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://help.security.gallagher.com/knowledge-hub/products/cc-software/configure/interface-options/api/representational-state-transfer-rest-api/rest-api-what-is-an-api-key.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.