I have been recently working with Sergey Chernyshev, who is the author of ShowSlow, on a new support for uploading HTTP tracing data (collected by the Net panel in Firebug) to the ShowSlow server.
This neat feature simply allows to upload the data in HAR format to the server and share them with others online.
Note that similar thing (uploading and sharing of measured data) is also supported by YSlow and PageSpeed (also using ShowSlow).
Another good news is that ShowSlow is an open source (I love open source!) and so, if you want to keep your data private while having the advantage of simple sharing (and other nice ShowSlow fetures), you can download and install your own copy of ShowSlow server (and also avoid limited upload history on the public instance).
So, read more if you are interested.
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Page load performance is largely important topic these days and virtually touches every web developer. In this post, I am going to show several page-load cases and describe how to properly read (analyze) data provided by the Net panel in Firebug.
Just to quickly summarize, the purpose of the Net panel is to intercept network communication between a web-page and the server and see what's going on under the hood. All created reports (logs) can be exported by NetExport extension (in HAR format) and there is also an online viewer allowing to preview all exported logs in graphical form.
In order to put together all following examples (HTTP activity logs) I used:
Firefox 3.6 + Firebug 1.5 + NetExport 0.7.
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We have been working with Simon Perkins and Steve Souders on an open format for exporting HTTP tracing information. It's called HTTP Archive (HAR) and we have just finished spec v1.1.
The format is already supported by Firebug (with NetExport extension installed), HTTPWatch 6.2 and also DebugBar 5.3. Further tools like Show Slow and Cesium could be the next.
The key idea is to have a common format for archiving HTTP information that are captured by HTTP sniffers. These logs contain valuable info about page load performance and can be further used to analyze and optimize weaknesses of the monitored page.
There is already a few blog posts about this, explaining all details and so, let me just summarize the most important links here.
Links
HAR Specification
HAR Discussion Group (first post moderated)
HAR Viewer Online preview of *.har files.
NetExport Firebug Extension for exporting HTTP logs.
Recommended Firebug Configuration: Firebug 1.5a26+, NetExport 0.7b5

About a month ago, I wrote a post introducing a HTTP Archive format that is used to export data from Firebug's Net panel.
Since that time we have made further progress and following info could be useful for all who are dealing with HTTP tracing logs and page load performance.
- NetExport - (requires Firebug 1.4a26 and higher) an extension that allows exporting HTTP tracing data from Firebug. This extension appends a new Export button into Firebug's Net panel toolbar (see the screenshot bellow).
- HTTP Archive Viewer - online tool that allows previewing of existing logs. The viewer uses the same visual style for visualizing HTTP tracing data as the Net panel. Note that it's possible to compare tracing info generated by multiple pages (which is also something what is planned for Firebug 1.5)
- HTTP Archive Format - description of the format for exported data (doc updated according to feedback we've got).
NetExport

HTTP Archive Viewer
