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.
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).
|Enabled/Disabled|| ||Enables the Net Panel|
|Disable Browser Cache|| ||Disables/enables browser HTTP cache.|
|Show Paint Events|| || 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
|Show BFCache Responses|| ||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.
Break On XHR
Removes all entries of the list of requests.
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.
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:
|All||Displays all requests||All|
|HTML||Limits display to markup files||(X)HTML, XML, MathML, RSS, RDF|
|CSS||Limits display to CSS files||CSS|
|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
⌘ while clicking the filter buttons. This feature was added in Firebug 1.12.
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.
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. 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:
|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|
Besides that there is a summary at the bottom of the Request List. This summary contains info about the total number of requests, the total file size and the total page load time.
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:
|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 |
|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|
There can be also other tabs coming from Firebug extensions. An example is a Cookies tab that shows all sent and received cookies for a request. This tab comes from the Firecookie extension.
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:
|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|
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.
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.
|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|
|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 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 |
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.
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.
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:
| ||Response content of the POST request|
|<parameter name>||Parameters used within the POST request|
Request list header
|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|
|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 (added in 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 |
|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.