---
title: ua-restriction
keywords:
  - Apache APISIX
  - API Gateway
  - UA restriction
description: The ua-restriction Plugin restricts access to upstream resources using an allowlist or denylist of user agents, preventing overload from web crawlers and enhancing API security.
---

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<head>
  <link rel="canonical" href="https://docs.api7.ai/hub/ua-restriction" />
</head>

## Description

The `ua-restriction` Plugin supports restricting access to upstream resources through either configuring an allowlist or denylist of user agents. A common use case is to prevent web crawlers from overloading the upstream resources and causing service degradation.

## Attributes

| Name           | Type          | Required | Default      | Valid values            | Description                                                                     |
|----------------|---------------|----------|--------------|-------------------------|---------------------------------------------------------------------------------|
| bypass_missing | boolean       | False    | false        |                         | If true, bypass the user agent restriction check when the `User-Agent` header is missing. |
| allowlist      | array[string] | False    |              |                         | List of user agents to allow. Support regular expressions. At least one of the `allowlist` and `denylist` should be configured, but they cannot be configured at the same time.   |
| denylist       | array[string] | False    |              |                         | List of user agents to deny. Support regular expressions. At least one of the `allowlist` and `denylist` should be configured, but they cannot be configured at the same time.   |
| message        | string        | False    | "Not allowed" |  | Message returned when the user agent is denied access.    |

## Examples

The examples below demonstrate how you can configure `ua-restriction` for different scenarios.

:::note

You can fetch the `admin_key` from `config.yaml` and save to an environment variable with the following command:

```bash
admin_key=$(yq '.deployment.admin.admin_key[0].key' conf/config.yaml | sed 's/"//g')
```

:::

### Reject Web Crawlers and Customize Error Message

The following example demonstrates how you can configure the Plugin to fend off unwanted web crawlers and customize the rejection message.

Create a Route and configure the Plugin to block specific crawlers from accessing resources with a customized message:

```shell
curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id": "ua-restriction-route",
    "uri": "/anything",
    "plugins": {
      "ua-restriction": {
        "bypass_missing": false,
        "denylist": [
          "(Baiduspider)/(\\d+)\\.(\\d+)",
          "bad-bot-1"
        ],
        "message": "Access denied"
      }
    },
    "upstream": {
      "type": "roundrobin",
      "nodes": {
        "httpbin.org:80": 1
      }
    }
  }'
```

Send a request to the Route:

```shell
curl -i "http://127.0.0.1:9080/anything"
```

You should receive an `HTTP/1.1 200 OK` response.

Send another request to the Route with a disallowed user agent:

```shell
curl -i "http://127.0.0.1:9080/anything" -H 'User-Agent: Baiduspider/5.0'
```

You should receive an `HTTP/1.1 403 Forbidden` response with the following message:

```text
{"message":"Access denied"}
```

### Bypass UA Restriction Checks

The following example demonstrates how to configure the Plugin to allow requests of a specific user agent to bypass the UA restriction.

Create a Route as such:

```shell
curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id": "ua-restriction-route",
    "uri": "/anything",
    "plugins": {
      "ua-restriction": {
        "bypass_missing": true,
        "allowlist": [
          "good-bot-1"
        ],
        "message": "Access denied"
      }
    },
    "upstream": {
      "type": "roundrobin",
      "nodes": {
        "httpbin.org:80": 1
      }
    }
  }'
```

Send a request to the Route without modifying the user agent:

```shell
curl -i "http://127.0.0.1:9080/anything"
```

You should receive an `HTTP/1.1 403 Forbidden` response with the following message:

```text
{"message":"Access denied"}
```

Send another request to the Route with an empty user agent:

```shell
curl -i "http://127.0.0.1:9080/anything" -H 'User-Agent: '
```

You should receive an `HTTP/1.1 200 OK` response.