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Intercept requests with specific headers

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By default, Dev Proxy intercepts all requests that match the URLs configured in the devproxyrc.json file. When you want to intercept only specific requests, such as requests issued by a specific component, you can configure Dev Proxy to intercept requests with specific headers.

To intercept requests with specific headers, in the devproxyrc.json file, add the filterByHeaders property. In the filterByHeaders property, specify the headers that you want to use to filter the requests. For each header, specify the value that the header should contain for Dev Proxy to intercept the request. If you leave the value empty, Dev Proxy intercepts requests that contain the specified header, regardless of its value.

Example: Intercept requests with a specific header and value

The following example demonstrates how to configure Dev Proxy to intercept requests that contain the x-app header with a value that contains contoso-intranet:

{
  "$schema": "https://raw.githubusercontent.com/microsoft/dev-proxy/main/schemas/v0.21.0/rc.schema.json",
  "plugins": [
    // [...] trimmed for brevity
  ],
  "filterByHeaders": [
    {
      "name": "x-app",
      "value": "contoso-intranet"
    }
  ]
}

Using this configuration, Dev Proxy intercepts requests that contain the x-app header with the value contoso-intranet, for example:

GET https://api.contoso.com/customers
x-app: contoso-intranet

Dev Proxy also intercepts requests that partially match the specified value, for example:

GET https://api.contoso.com/customers
x-app: contoso-intranet-search

Dev Proxy doesn't intercept the following request because the value of the x-app header doesn't contain contoso-intranet:

GET https://api.contoso.com/customers
x-app: contoso-public

Partial matching is convenient and allows you to intercept requests with values that can change over time, such as component or SDK version.

Example: Intercept requests with a specific header no matter the value

To intercept requests that contain a specific header, regardless of its value, leave the value empty:

{
  "$schema": "https://raw.githubusercontent.com/microsoft/dev-proxy/main/schemas/v0.19.0/rc.schema.json",
  "plugins": [
    // [...] trimmed for brevity
  ],
  "filterByHeaders": [
    {
      "name": "x-contoso",
      "value": ""
    }
  ]
}

Using this configuration, Dev Proxy intercepts requests that contain the x-contoso header, regardless of its value:

GET https://api.contoso.com/customers
x-contoso: api-sdk v1.0

Or:

GET https://api.contoso.com/customers
x-contoso: intranet

Dev Proxy doesn't intercept the following request because it doesn't have the x-contoso header:

GET https://api.contoso.com/customers
x-app: contoso-public