Released: Modify Headers

Bug fix release:

  • #24593: Addon toolbar is displayed after marking it closed when new window is opened

Please download from Mozilla Addons.

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Released: Modify Headers

I’m pleased to announce version of Modify Headers. Highlights include:

  • icon New icon: thanks to dodihanz for the design.
  • Click the small Modify Headers icon in the addon toolbar to open a quick menu.
  • "Always On" preference is replaced by a Start/Stop button.
  • Start/Stop Modify Headers by clicking the icon in the main window or using the menu from the addon bar.
  • There are also a couple of bug fixes.

As always, go to to open any new bugs.

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Vote for your Favourite

Voting is now open for a Modify Headers icon. Pick the one you like the best by Wednesday November 9, 2011.

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An Icon for Modify Headers

It’s time for Modify Headers to have it’s own icon. I have started a project at asking designers to provide ideas for an icon from which the best one will be chosen.

The project will run for two weeks until November 5, 2011 and as icons are submitted, they will appear in the public gallery. Towards the end of the project a set will be chosen and put out to a vote. I’ll post the link to the voting site once it is ready.

In the mean time, feel free to take a look at the entries and make any comments on this blog post.

I’m really excited about getting the icon as I’ve wanted to do it for a while.

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Released: Modify Headers 0.6.12 and 0.7.0beta1

There are 2 releases this week. Version 0.6.12 provides backwards compatibility for Firefox 3.0. Versions 0.6.8 – 0.6.11 used a native JSON library not bundled with Firefox 3.0.

Version 0.6.12 of Modify Headers is the last version that will support Firefox 3.0.

Modify Headers 0.7.0beta1 contains the first of the configuration UI improvements:

  1. Headers can be reordered using drag and drop.
  2. When adding a new entry, the header name field provides auto-completion.
  3. The auto-complete is pre-populated with common HTTP request header names.

Both versions can be downloaded from, 0.7.0beta1 is available from the beta channel.

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Modify Headers Roadmap 2011

Here is a summary of the main releases expected this year for Modify Headers:

  • 0.6.10: Seamonkey 2.0 support, re-sizable columns, improved JS code. Currently available in the beta channel.
  • 0.7.0: Header sorting and re-ordering, icon in the Addon/Status bar. A proper logo.
  • 0.7.5: HTTP request creation tool to support POST, HEAD and other verbs.
  • 0.8.0: Site profiles.

Other ideas for features that require lots of investigation include:

  • Support for Firefox Mobile.
  • Integration with Selenium.

If you have any ideas for new features you would like to see, please post to

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Released: Modify Headers Version 0.6.9

Version 0.6.9 of Modify Headers has been released and is available at

This version fixes two problems from 0.6.8:

  • Open-As-Tab has been re-established.
  • The Modify Headers window can now be resized.
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Problems with Modify Headers 0.6.8 Window

A fair few people have contacted me regarding some of the changes in Modify Headers 0.6.8. So here is an update regarding the changes and what is happening to fix them.

Change 1: Not allowing the Modify Headers window to resize.
The addon window was switched to use a special type of window called a prefwindow. This is so a toolbar can be shown above the content using the same style as in the Firefox Preferences window. This is in preparation for when site specific profiles will be added to the addon. In the Preferences System documentation, the suggested mechanism for opening the window is:

var features = "chrome,titlebar,toolbar,centerscreen,modal";
window.openDialog(url, "Preferences", features);

This results in the window not being resizeable when it is opened. I tried long and hard before the release of 0.6.8 to find a combination of options that enabled the window to be resizeable, including use of the “resizeable=yes” feature. But I was unable to find the solution.

Change 2: Disabling the Open-As-Tab feature
The switch to using the prefwindow caused the browser to resize when opened in a tab. You can test this yourself by pasting chrome://modifyheaders/content/preferences.xul in a new tab. I felt that this was not a desirable behaviour when opening the addon in a new tab and decided to disable it while finding a solution.

With both changes, I decided the best way forward was to release the new version to provide the Firefox 4 support and press forward to find fixes and follow-up quickly with a new release.

What’s being done?

I can confirm that fixes for both issues have been found and are going through final testing. A beta release with these updates is available at Scroll down until you see the section called Beta channel below the image gallery.

Release 0.6.9 will be uploaded to very soon.

Note: if you install the beta, you will then continue to get ONLY beta releases until you switch back to the main release. Beta versions do not go through the Mozilla review process, so please be sure you want to get beta versions before installing this.

Finally, my apologies if this has caused any problems for users. In future, I will make use of the beta channel to test out new ideas and to work out problems. Hopefully, a few of you will be kind enough to install the beta and provide feedback.

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Released: Modify Headers 0.6.8

Just before the release of the new version, Modify Headers hit One Million Downloads at Thank you to everyone who has downloaded the addon and uses it regularly for whatever you need. Getting to this milestone spurs me on to continue development of new and improved features.

Version 0.6.8 of Modify Headers has been released at If you already have the addon installed, Firefox will automatically update.

Changes in this version:

  • Refactoring to support Firefox 4
  • An Improved preferences window
  • Rewritten Export/Import wizard. JSON is now used as the export format. The old XML export format can still be imported for backwards compatibility
  • The Open in a new tab preference has been discontinued due to a problem on Macs

Plans for the next version include:

  • Drag and Drop re-ordering
  • Icons for the preference bar

If you need help, please see the help pages. These pages require updating for the latest version. Please be patient while this is in progress.

Posted in Mobile Web, Uncategorized | 3 Comments

Firefox Addons Update

I’ve been getting a few requests for an update on Modify Headers, so here we go:

  • Follow occasional updates on Twitter at
  • The update for Firefox 4 is complete. Before submitting to Mozilla, the export/import facility is getting a much needed overhaul.
  • The export function is complete and the import function is under development.
  • The Open in a new tab feature has been disabled due to problems on Macs with prefwindow. The configuration will open only as a separate window in the next version.
  • The help pages hosted at are failing. disabled PHP due to a security concern on their platform.
  • I will move the hosting for the help pages to this website, come back soon for an announcement of the URL.

Once the new version of Modify Headers is submitted to AMO, I’ll start on the update for XHTML Mobile Profile.

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