# Inspecting server-sent events

[Server-sent events](https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events) allow for an inversion of the traditional client-initiated web request model, with a server sending new data to a web page at any time by pushing messages. You can inspect server-sent events and their message contents using the {doc}`Network Monitor <../index>`. This article shows you how.

## Inspecting the SSE network activity

When you are viewing a document that is receiving server-sent events, you can go to the Network Monitor, select the file that is sending the server-sent events, and view the received messages in the *Response* tab on the right-hand panel.

```{image} basic-sse-message-view.png
:class: border
```

At the top of the panel there is a trash can icon, which allows you to trash the messages sent so far, and a filter field in which you can enter a text string to filter the displayed messages by.

## Viewing the message contents

Select one of the messages listed in the *Response* tab, and you'll see the message contents displayed at the bottom of that same tab.

```{image} see-message-detail-view.png
:class: border
```

In the above example, you can see that JSON and raw data representations of the content are shown. For a plain text message, you'd just see a raw data section.

The supported data formats are as follows:

- Mercure protocol
- JSON

## Customizing the displayed columns

For each message, you'll see *Data* and Time columns by default, but you can right-click on the table header to bring up a context menu in which you can toggle columns on and off, and reset it back to its original state.

```{image} customize-columns.png
:class: border
```

The available columns are as follows:

- *Data*: A summary of the contained message data.
- *Size*: The size of the message.
- *Time*: A timestamp representing when the message was sent.
- *Event Name*: The name of the event type that resulted in the message being sent (e.g. `` `message` `` or `` `ping` ``).
- *Last Event ID*: The ID of the last event that was fired.
- *Retry*: The interval after which failed message will be resent.

## Network Monitor features

The following articles cover different aspects of using the network monitor:

- {doc}`Toolbar <../toolbar/index>`
- {doc}`Network request list <../request_list/index>`
- {doc}`Network request details <../request_details/index>`
- {doc}`Network traffic recording <../performance_analysis/index>`
- {doc}`Throttling <../throttling/index>`
- {doc}`Inspecting web sockets <../inspecting_web_sockets/index>`