---
title: "Real User Network Error Logging"
slug: "real-user-network-error-logging"
updated: 2023-01-06T15:49:07Z
published: 2023-01-06T15:49:07Z
canonical: "docs.catchpoint.com/real-user-network-error-logging"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.catchpoint.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Real User Network Error Logging

Catchpoint RUM can detect when end users are unable to access applications due to various problems such as DNS failures, connection timeouts/resets, page abandonment, and HTTP errors. Network Error Logging in RUM provides a great complement to node-based tests where the same errors can be detected proactively from predetermined vantage points.      [Network Error Logging (NEL)](https://w3c.github.io/network-error-logging/) defines a response header declaring a reporting policy. The user agent leverages the header and policy to report network errors back to Catchpoint.

## Configuration
To start using NEL, configure your application to respond with the following HTTP headers: 
`Report-To: {"group":"network-errors","max_age":2592000,"endpoints":\[{"url":"https://r.3gl.net/hawklogserver/**\<app id\>**/re.p"}\]}`

`NEL: {"report_to":"network-errors","max_age":2592000,"success_fraction":0,"failure_fraction":1.0, "include_subdomains": true}`

- Policy setting only works for webpages that use HTTPS.
- Reporting endpoint must also be HTTPS, otherwise, browser throws it out.
- Abandoned requests can be caused by rendering engine logic that precaches and preloads URLs.

The **app id** should be replaced with your RUM app's id from the Catchpoint portal. This can be found in the properties page for the RUM app you wish to capture errors for. 

**Note**: The **Restrict NEL Collection** option in **App Details** should be disabled to collect NEL data.

## Analysis

Once this data is captured, it can be viewed in Explorer as well as the RUM Smartboard.
<img src="https://cdn.document360.io/cb4af8f9-6751-4fd2-b39c-07aae832badb/Images/Documentation/360012265212-mceclip1.png" width="1560" height="645" />
<img src="https://cdn.document360.io/cb4af8f9-6751-4fd2-b39c-07aae832badb/Images/Documentation/360012264351-mceclip0.png" width="861" height="393" />

## Configure NEL in Fastly 

To configure NEL for Fastly, please follow the steps below:
1. Log in to your fastly.
2. Click **Configure** in the main menu.
3. Select your service from the **Service** pulldown.
4. Click on the blue **Configuration** menu on the top right and select  "Clone Active"
5. Click **Content** 
    ![](https://cdn.document360.io/cb4af8f9-6751-4fd2-b39c-07aae832badb/Images/Documentation/360012590472-mceclip1.png)
6. Click **Creater Header**
![](https://cdn.document360.io/cb4af8f9-6751-4fd2-b39c-07aae832badb/Images/Documentation/360012594871-mceclip0.png).
7. Enter the values as shown in the screenshot.
    - Make sure that json string has quotes escaped with `%22`
    - Make sure the json ins enclosed n quotes  (`""`)
    - Example: ***`"{%22report_to%22:%22network-errors%22,%22max_age%22:2592000,%22success_fraction%22:0,%22failure_fraction%22:1.0,%22include_subdomains%22: true}"`***
![](https://cdn.document360.io/cb4af8f9-6751-4fd2-b39c-07aae832badb/Images/Documentation/360012595031-mceclip3.png)
8. Click **Save**
9. Do the same for each header
10. Click **Activate**
**![](https://cdn.document360.io/cb4af8f9-6751-4fd2-b39c-07aae832badb/Images/Documentation/360012590532-mceclip2.png)**