Net Panel

Net Panel

The main purpose of the Net Panel is to monitor HTTP traffic initiated by a web page and simply present all collected and computed information to the user. Its content is composed of a list of entries where each entry represents one request/response round trip made by the page.

Options Menu

This menu is reachable via the little arrow in the panel tab ( ) or by right-clicking on on the panel tab (since Firebug 1.9).

Option	Preference	Description
Enabled/Disabled	extensions.firebug.net.enableSites	Enables the Net Panel
Disable Browser Cache	browser.cache.disk.enable browser.cache.memory.enable	Disables/enables browser HTTP cache.
Show Paint Events	extensions.firebug.netShowPaintEvents	Specifies whether DOM paint events shall be shown as vertical lines inside the Net Panel Note: Due to a security issue these events are not sent to web content anymore by default. You need to set dom.send_after_paint_to_content to true in order to see them.
Show BFCache Responses	extensions.firebug.netShowBFCacheResponses	Specifies whether HTTP responses coming from the BFCache should be displayed.

For more info about tweaks available in Firebug please see the full list of preferences.

Panel Toolbar

Break On XHR

Clicking the "Break On XHR" button ( ) enables a listener for XMLHttpRequests. If an XHR is made then, the debugger stops the script execution immediately and jumps to the Script Panel.

Clear

Removes all entries of the list of requests.

Persist

When this option is enabled, the entries of the requests list are not deleted when reloading the page. Instead the are grouped by page request, which means, when reloading the page several times you will get several request trees having the page title as root.

Filters

There are several buttons for filtering the current list of requests for giving a fast overview over the files you want to see. Following there's a list of the currently implemented filters:

Filter	Description	file types
All	Displays all requests	All
HTML	Limits display to markup files	(X)HTML, XML, MathML, RSS, RDF
CSS	Limits display to CSS files	CSS
JavaScript	Limits display to JavaScript files	JS
XHR	Limits display to XMLHttpRequests	XMLHttpRequests
Images	Limits display to image files	JPEG, PNG, GIF, BMP
Plugins	Limits display to Flash and Silverlight files	SWF, XAP
Media	Limits display to media files	MP3, Ogg, WAV, MIDI, WebM, MPEG, FLV
Fonts	Limits display to font files	WOFF, TTF, OTF

You can also select multiple filters by holding down Ctrl / ⌘ while clicking the filter buttons. This feature was added in Firebug 1.12.

Search

You have the possibility to search inside the different requests. Thereby besides the general options for case sensitivity and regular expression search you can optionally also search inside the request bodies.

Request List

The main part of the Net Panel is the Request List. When the Net Panel is activated and a page is loaded it starts filling with all HTTP requests made by a page in the order of they were started. Each entry displays basic info about the request and a graphical Timeline that depicts load phases in time. The following is a list of information, that is displayed for each request:

• HTTP request method
• HTTP response code and description
• Requested file name (shortened; hovering it shows the entire URL)
• Domain name from where the response came from
• Size of the response (compressed size in case of compressed responses)
• Graphical Timeline and load time info

Depending on their loading status and source the requests are displayed differently:

Filter	Description	Example
Normal finished requests	Requests fetched from the server
Loading requests	Requests currently being fetched from the server
Cached requests	Requests with response coming from the browser cache (HTTP status code 304)
BFCached requests	Requests with response coming from the BFCache
Erroneous requests	Requests, which returned an HTTP error (HTTP status code 4xx or 5xx)
Aborted requests	Requests, which were aborted by the client

Request summary

Below the requests there is a summary at the bottom of the Request List.

This summary contains several pieces of information:

• total number of requests
• total size of requests
• size of requests read from the browser cache
• total page load time (time elapsed from the start time of the first request until the last request finished loading; can increase after the page was fully loaded e.g. through XHRs, dynamically added images, etc.)
• 'onload' event time (time elapsed from the start time of the first request until the load event was fired)

Request & Response Details

Every request entry can be expanded by clicking on the left hand twisty in order to see additional info. It's important to note that the entry actually represents both: the request sent to the server and also the response coming back. No matter if it comes from the server or the browser cache, one request-response round-trip is represented by one entry in the list. There are several tabs shown for each request. Depending on the request method and requested file type there are additional tabs with further information. Here's a list of the tabs shown for the different requests:

Tab	Restriction	Description
Headers	-	Lists the request and response headers of the current request
Response	-	Displays the contents of the response unformatted (as they came from the server)
Params	GET request	Displays the URL parameters
Post	POST request	Displays the POST parameters in a formatted way (depending on the Content-Type of the request) and the raw data inside the Source section
HTML	HTML files	Displays the rendered HTML output
JSON	JSON files	Displays the JSON data in a formatted tree structure similar to the DOM Panel
XML	XML files	Displays the XML data in a formatted tree structure similar to the HTML Panel
Cache	Cached files	Lists cache information to the current request
Cookies	Requests with cookies	Lists the cookie information sent together with the request

There can be also other tabs coming from Firebug extensions.

Cache Info

Some files are fetched from the browse cache. They can be recognised by the response status "304 Not Modified". The Cache Tab includes the following information:

Info	Description
Last Modified	Last time the cache entry was modified
Last Fetched	Last time the cache entry was accessed
Expires	Expiration time of the cache entry
Data Size	Cache entry data size
Fetch Count	Number of times the cache entry has been accessed
Device	ID for the device that stores this cache entry

Timeline

One of the most useful features for debugging page load performance is a request Timeline. The Net Panel uses this graphical representation to show request load in time together with timing data.

Request Timeline

Every request-response round trip is shown as horizontal bar in the Timeline and is composed of several phases, represented by different colors. Hovering a Request Timeline offers more detailed information about the timings of the different phases.

Value	Display	Description
Blocking		Time spent in a browser queue waiting for a network connection (formerly called Queueing) For SSL connections this includes the SSL Handshake and the OCSP validation step.
DNS Lookup		DNS resolution time
Connecting		Elapsed time required to create a TCP connection
Sending		Sending request headers
Waiting		Waiting for a response from the server
Receiving	/   (from cache)	Time required to read the entire response from the server (and/or time required to read from cache)
'DOMContentLoaded' (event)	(blue line)	Point in time when the DOMContentLoaded event was fired (since the beginning of the request, can be negative if the request has been started after the event)
'load' (event)	(red line)	Point in time when the page load event was fired (since the beginning of the request, can be negative if the request has been started after the event)
'MozAfterPaint' (event)	(green line)	Point in time when a MozAfterPaint event was fired (since the beginning of the request, can be negative if the request has been started after the event)
Time stamp	(olive line)	Time stamp created via console.timeStamp()

Waterfall Graph Time Extent

In order to keep the X axis (time) in sensible extent, the waterfall graph breaks the time and starts displaying new requests that start later (in the page life) again from the beginning. In other words, a request, that starts after a predefined period of time (1s by default) since the previous request finished, starts from 0 time of the graph again. This avoids endless extension of the X axis, which would make the graph less readable. There is a preference extensions.firebug.netPhaseInterval allowing you to set the gap in milliseconds, after which the time break should happen. If set to 0, breaking doesn't happen at all.

Breakpoint Column

Setting breakpoints

The Breakpoint Column allows you to set breakpoints for XMLHttpRequests. By clicking on it a breakpoint is set for the request. Clicking it again removes the breakpoint again.

Breakpoint conditions

You can create a conditional breakpoint by right-clicking a breakpoint. Doing so opens the Breakpoint Condition Editor:

There are variables available, which can be used within the expression:

Variable	Description
$postBody	Response content of the POST request
<parameter name>	Parameters used within the POST request

Context Menu

Request list header

Option	Description
URL	Toggles the display of the column for the URL of the requests
Status	Toggles the display of the column for the HTTP status of the requests
Protocol	Toggles the display of the column for the protocol of the requests
Domain	Toggles the display of the column for the domain of the requests
Size	Toggles the display of the column for the size of the responses
Local IP	Toggles the display of the column for the client's IP of the request
Remote IP	Toggles the display of the column for the server IP of the request
Timeline	Toggles the display of the column for the Timeline of the request
Reset Header	Resets the column display to the default

Requests

Option	Context	Description
Copy Location	all requests	Copies the URL of the request to the clipboard
Copy URL Parameters	requests with URL parameters	Copies the URL parameters of the request to the clipboard
Copy Location with Parameters	POST requests	Copies the URL including the parameters to the clipboard
Copy POST Parameters	POST requests	Copies the POST parameters to the clipboard
Copy Request Headers	all requests	Copies the headers of the request to the clipboard
Copy Response Headers	all requests	Copies the headers of the response to the clipboard
Copy Resonse Body	text file requests	Copies the response body to the system clipboard
Copy as cURL	all requests	Copies the request as a cURL command to the clipboard Firebug 1.12
Open in New Tab	all requests	Opens the resource in a new browser tab (uses the same HTTP method as the original request)
Open Response in New Tab	text file requests	Opens the response in a new browser tab
Stop Loading	loading requests	Stops loading the request
Resend	all requests	Sends the request again
Use in Command Line	all requests	Focuses the Command Line and makes the request available as $p.
Inspect in Script Panel	JavaScript requests	Allows to inspect the requested JavaScript inside the DOM Panel
Inspect in CSS Panel	CSS requests	Allows to inspect the requested style sheet definition inside the DOM Panel
Inspect in DOM Panel	all requests	Allows to inspect the request inside the DOM Panel
Break on XHR	XMLHttpRequests	Toggles the breakpoint for the request
Edit Breakpoint Condition...	XMLHttpRequests with set breakpoint	Opens the dialog for setting a conditional breakpoint

Copying a request as a cURL command

cURL is a command line tool for transferring data with URL syntax. Firebug's Copy As cURL command recreates the HTTP request (including HTTP headers and query string parameters) and copies it as a cURL command string to the clipboard.
The string can be pasted into a terminal window to execute the same request or for example pasted to a client that supports cURL.
In cases where the server serves compressed responses the preference net.curlAddCompressedArgument can be set to true and Firebug will add the --compressed argument to the generated command string.

• cURL's homepage

See also

• Internal architecture of the Net panel
• Explanation of the Net panel timings on softwareishard.com