---
title: "Check CDN Performance"
sidebar_label: "Check CDN Performance"
description: "How to self-test your CDN resource and content download speed, and how to request diagnostics"
sidebar_position: 1
---

import Formbricks from '@theme/MDXComponents/Formbricks'

# Check CDN Performance

If you encounter errors or slow content loading via CDN, check the following:

* [balance](#check-balance);
* [CDN resource](#check-cdn-resource);
* [content download speed](#check-content-download-speed) from the origin and via CDN.

## Check balance \{#check-balance}

1. In the [control panel](https://my.selectel.ru/cdn-v3), on the top menu, click **Products** and select **CDN**.
2. Check your account balance in the top-right corner and the CDN resource status. If the balance is negative and the CDN resource is in `INACTIVE` status, the CDN resource was disabled for non-payment.
3. To enable the CDN resource, [top up your balance](/balance-and-payments/manage/top-up-balance.mdx) to cover the debt, then [enable the CDN resource](/cdn/resources/enable-resource.mdx).

## Check CDN resource \{#check-cdn-resource}

The check will show the CDN resource status, the correctness of the CNAME record, and the availability of the file from the origin and CDN server.

1. In the [control panel](https://my.selectel.ru/cdn-v3), on the top menu, click **Products** and select **CDN**.

2. Check the [status](/cdn/resources/check-resource-status.mdx) in the CDN resource row. If the resource status is `ERROR` or it is stuck in one of the statuses, [create a ticket](https://my.selectel.ru/tickets/create).

3. Open the file on the content source using a link like `example.com/images/image.png`. If the file does not load, the issue is on your website side.

4. Open the file via the default domain using a link like `*.selcdn.net/images/image.png`. The default domain can be found in the [control panel](https://my.selectel.ru/cdn-v3/resources): in the top menu, click **Products** → **CDN** → resource row. If the file does not load, check the [Host header](/cdn/source/manage-host-header.mdx).

5. Open the file via a custom domain using a link like `cdn.example.com/images/image.png`. You can view the custom domain in the [control panel](https://my.selectel.ru/cdn-v3): in the top menu click **Products** → **CDN** → resource string. If the file does not load, check that the domain [CNAME record](/cdn/resources/add-personal-domain.mdx) is correct.

## Check content download speed \{#check-content-download-speed}

When you access content from the origin for the first time, loading the file takes longer than during subsequent requests, when the file is served from the cache.

1. Ensure that you have disabled VPN or proxy on the device you are using for testing — these can slow down the download speed.

2. Check the download speed from the origin:

   2.1. Open the file on the content origin.

   2.2. View the file download speed; to do this, open developer tools in your browser → **Network** tab → view the value in the **Time** column.

3. Upload the file to the CDN cache; to do this, open the file on a [domain](/cdn/resources/domains.mdx) used for delivering content via CDN. Domains can be viewed in the [control panel](https://my.selectel.ru/cdn-v3): in the top menu click **Products** → **CDN** → the CDN resource page → the **General** tab.

4. Check the download speed from the CDN cache:

   4.1. Open the same file on the CDN domain that you opened in step 3.

   4.2. View the file download speed; to do this, open developer tools in your browser → **Network** tab → view the value in the **Time** column.

5. Compare the download speed of the file from the source and from the CDN cache. If the download speed via CDN is higher than or equal to the download speed from the source, the CDN is working correctly. If the download speed via CDN is lower, [submit a diagnostic request](#submit-diagnostic-request).

## Request diagnostics \{#submit-diagnostic-request}

1. Record an HTTP session demonstrating the CDN error in HAR file format. For more details on recording a HAR file for Edge, Firefox, or Chrome, see the instructed [How to get a HAR file](https://toolbox.googleapps.com/apps/har_analyzer/?lang=ru) on the Google Admin Toolbox portal.

2. [Create a ticket](https://slc.tl/6cnik) to request diagnostics. Provide the following in the ticket:

   * CDN resource name;
   * link to the file on the domain used for content delivery via CDN;
   * HAR file that you created in step 1;
   * scale of the issue and the location of users experiencing it.

<Formbricks />