> ## Documentation Index > Fetch the complete documentation index at: https://docs.requestly.com/llms.txt > Use this file to discover all available pages before exploring further. # GraphQL Support > Learn to modify GraphQL API requests and responses using Requestly Interceptor to debug and test GraphQL APIs. *** Unlike REST APIs, GraphQL APIs provide a flexible approach to querying and mutating data through a single endpoint. They allow clients to specify exactly what data is needed, reducing over-fetching and under-fetching issues common with REST APIs. GraphQL APIs can be modified to customize requests and responses for testing and debugging. This guide provides detailed steps to achieve this using Requestly Interceptor. ## Modifying GraphQL Responses In GraphQL, client interactions are typically managed through a single HTTP endpoint. The specific operation to execute is often indicated by the `operationName` field in the request payload. **Example Request** ```bash theme={null} POST { "operationName": "getUsers", "query": ` query getUsers { users { id email } } ` } ``` To modify the response of a GraphQL API: ### Steps to Modify API Response Navigate to the HTTP Rules section in the web or desktop app. Click on "+ New Rule" and select **Modify API Response**. Choose "GraphQL API" as the Resource Type. In the **GraphQL Operation (Request Payload Filter)** section: * Enter **Key** as `operationName`. * Enter **Value** as the operation name you want to target (e.g., `getUsers`). Define the new response you want to serve for the specified operation. Click **Save** to store the rule and toggle it ON to apply the changes. Validate the rule by sending a request matching your conditions and verifying the modified response. For additional details, visit the Modify API Response Rule Page. **Notes** * The **Key** represents the JSON key in the request payload and supports nested paths. For example: * If `operationName` is located at `data.operationName`, specify `data.operationName`. * For array payloads, such as `[{"operationName": "value"}]`, use `0.operationName` as the key. * If the request does not include `operationName`, select **Resource Type** as "REST API" and use **Dynamic (JavaScript) Mode** to filter and modify the response. ### Example Without `operationName` In cases where the operation is specified within the `query` field: ```bash theme={null} POST /graphql { "query": ` query getUsers { users { id email } } ` } ``` You can modify the response using a JavaScript snippet: ```jsx theme={null} function modifyResponse(args) { const { url, response, requestData, responseJSON } = args; if (requestData.query?.includes("query getUsers")) { console.log("Requestly Interceptor: Modifying response", { query: requestData.query }); return { ...responseJSON, custom: true }; } return response; } ``` *** ## Modifying GraphQL Requests If you need to alter the GraphQL query or its variables, use the **Modify Request Body** rule to change the request payload dynamically. ### Steps to Modify Request Body Navigate to the HTTP Rules tab in the web or desktop app. Click on "+ New Rule" and select **Modify Request Body**. Choose "GraphQL API" as the Resource Type. In the **GraphQL Operation (Request Payload Filter)** section: * Enter **Key** as `operationName`. * Enter **Value** as the operation name you want to target (e.g., `getUsers`). Define the new Request you want to serve for the specified operation Click **Save** to store the rule and toggle it ON to apply the changes Validate the rule by sending a request matching your conditions and verifying the modified response. For additional details, visit the Modify Request Rule Page.