Firesizer (Firefox Extension)

Firesizer is an extension for the firefox web browser. It allows you to resize the browser window to specific dimensions.

It provides a menu and status bar to resize the window dimensions to a specific size. Unlike other similar extensions, this one sets the size of the *entire window*, not just the HTML area.

Heavily inspired by "Yet Another Window Resizer" by Galoca

Here's a screen-shot of what it looks like in firefox when loaded:


Firesizer is licensed under the same license as Firefox itself -- Using a triple license of MPL 1.1/GPL 2.0 or later/LGPL 2.1 or later.


To download and install this extension, please see the Firesizer extension page at

I am using Fireresizer and I am pleased with it. But there is one thing lacking that I need: positioning.

If each size setting could also have an associated screen position for the top-left corner of the browser window, that would make Fireresizer into the browser killer-app!

As I maintain my websites, I must have multiple windows open, including folder windows which I carefully position to avoid overlapping or any other obscuration.

Firefox needs to be repositioned as well as resized as I go through the editing and testing cycles. Adding repositioning would make my efforts so much more productive.

Is there any chance that you could add positioning?

Thank you for your kind attention

Julian (-_-)

I'm glad you found firesizer useful. If you position windows frequently, and get annoyed at how difficult it is to be precise when trying to line them up (and you're using Windows), you should find the excellent program allsnap a better tool to handle this. It does not remember the actual position of the windows, but it makes it much easier to position them right up against each other.

There also appears to be an extension that might do what you like right now. Take a look here at Custom Geometry

Hi Brian :-)

Thank you for your suggestions for allsnap and Custom Geometry. I shall try them.

But I still consider that if you could add positioning to Firesize, that would really complete it.

I would really prefer to use one extension that does it all. My guess is that others might think so too. Would it be that hard to do?

But thank you anyway for Firesizer - it's great and almost complete!

I just installed Firesizer but quickly found a usability enhancement: named sizes.

While the screen dimensions seem obvious (at least to me) and are easy to use "as is," other custom sizes would be even easier to use if they could be tagged. For example, instead of just listing the dimension "840x1140" (used for reading documents in a portrait orientation), it'd also be nice to see "Portrait." This feature would become more important with a large number of saved sizes.


Sam Brown

I have been using Firesizer for a long time and love it. Named labels would be a great idea.

I just found out about FireSizer and so far, the feature seems incredibly cool.

It seems that when I saved my first custom resolution with the "Save Current Size" command, it actually remembers the START POINT in the upper left corner. So even if I resize the window manually then close/exit Firefox, when I open Firefox again it starts right up in that same upper left corner position. So all I have to do then is right click on the status bar, choose my custom resolution (1182x1112 in my case) and I'm good to go.

I am not sure if that was programmed intentionally or not, but I'm glad it does that.

If possible, I would really appreciate the addition of these features to the already good program:

User can specify Origin by entering X/Y coordinates of the upper left corner of the Firefox window


A checkbox to toggle between opening Firefox window at the last known size (which it seems to do by default already) and a Forced window resize at startup (which I have to do manually now by right clicking on the status bar and choosing 1182x1112, for example)

I make these requests not to complain about what Firesizer lacks, but with the thought of making Firesizer even better than it already is.

I would hope that you please consider both of these requests, as I think by adding them, Firesizer would become a more complete solution for Firefox 3 users.

With these additions, I could rely on using Firesizer ONLY and not having to load other extensions for those features.

Thank you very much,


I'm glad you found firesizer useful. Firesizer does not remember the position of the windows, that is a function built-in to firefox. Firefox should also automatically start up at the same size as when you exited, which is also not a feature of firesizer. I will take a look into the idea of always having the browser start at a size that you choose (which would be different than the size when you closed firefox).

I posted earlier requesting that in addition to the window resizing option, you add the ability to define a START POSITION location so that the browser will be located on screen at the exact coordinates that the user specifies.

For instance, you currently have the ability to save the current window size, and that works well. It can be recalled at any time via the status bar.

I would really like to see you add the ability to define where on the computer screen Firefox will start.

I'm thinking a simple X,Y coordinate that forces the position of the Upper-Left corner of the window to a location the user specifies.

It might be something like:

Start Position: 103,64

and by setting that, you know that each and every time Firefox is started, it snaps the upper left corner of the window to the 103,64 coordinates.

I would really, really appreciate it if you would add this to what already is a great plug-in.

Please let me know if you are willing to incorporate that feature. It would be very helpful for those of us with limited screen size and we sometimes need to relocate and resize the Firefox window so that we can work in a multi-window environment.

For instance - when I want to type content that is in the existing Firefox window, I may open up Microsoft Word at 100% zoom size and want to push the Firefox window to the left and reduce the width of the window so that I can essentially have the browser window working side-by-side with my Word window.

When done with that, I'd like to be able to shut-down Firefox and have it snap back to the original coordinate location that I prefer for browsing fixed-width sites, such as AnandTech.

I really, really hope you will implement this feature. Firesizer is such a simple and elegant implementation and by adding this one new feature, it could become even more useful than it is already.

Thank you in advance for your time and your reply.


I've added your suggestion to my todo list for Firesizer, but I'm not promising that it will be implemented. Firesizer does one thing and does it well, and that's why it is simple and elegant. If more functions are added to it, that increases the complexity.

I have been using it.
Please add!

Format when you save them,

character code:UTF-8N ->without BOM(Byte Order Mark)
line feed code:LF

Thanks for the translation... I've added it to the most recent version (0.91) and uploaded it to Mozilla. It should hopefully come out in a few days.

Brilliant plugin, I recommend this to everyone I know who does any kind of web developing or general web pokery; just one thing I'd like in a future release.

Is there any chance we can have an option to display only an icon in the status bar for Firesizer, rather than the size text?


Is there any chance you’ll be updating firesizer to work with Minefield – would be appreciated

According to Wikipedia, "Minefield" is a code name that means "trunk (development) builds". It is not a specific version of Firefox. As these builds can change rapidly, I cannot keep firesizer compatible with them. Once a build reaches it's beta release, that is when I start to look to make sure it's compatible.

If you want to live dangerously (which you currently are by running trunk builds), you can disable extension version checking as described on this page: Extensions.checkCompatibility, but I can make no guarantees that firesizer will work (I think it probably will).

This is a nice idea. However, there is an issue.
The size in the status bar is displaying the size of the Firefox WINDOW, but not the size of the actual VIEWABLE AREA. For example things like the status bar, menu bar, bookmarks bar, tabs bar and side bars all take up room that makes the website actually SMALLER then the size given. In my case, I have my tabs on the left hand side of the screen going up and down, and this takes up more space in the window.
So what am I getting at? There should be TWO modes to Firesizer. One will calculate the screen size by how big the WINDOW is, and the other mode would calculate it by how big the actual viewable area is inside the window. For me, these two numbers would differ in several hundred pixels.
Thanks for the consideration...

Thanks for your input.

The issue you mention is by design. I use firesizer as part of my window management strategy, not to test to see if web sites fit on a certain sized screen. However, if that is your goal, you need to consider that everyone has some sort of tool bars, menus, etc... that take up space. If your goal is to design for a 1024x768 screen, sizing the HTML area to 1024x768 is the wrong thing to do.

There are other window resizer extentions available at that will resize the HTML area. Those existed before I wrote Firesizer, so one of those might meet your needs better.

Thanks for the reply.
If firesizer is not meant to do what I am looking for it to do, can you please link or name another add-on that can? I searched and your add-on comes up on the top every time (congrats) but I can't seem to find any alternatives.

If you search for "resize window", you will find a few options.

Thanks, using that search term, I was able to find three other extensions and gave each one a try (one at a time) However, they all did the same thing as your extension. In fact, Out of the four, yours worked the best, but they all did the same thing by resizing the window and not the viewable area. Any other ideas?

I know for a fact that Yet Another Window Resizer resizes the HTML area, and not the whole window, as that extension is what Firesizer is based on resizing the windows instead of the HTML area is why I wrote Firesizer. I have just tried it once again and that is what it does. YAWR does not create a status bar readout, it is only available under the "Tools" menu or the Right-click menu and is listed as "Resize Window".

Hey, Sorry for the long delay in reply but I just wanted to reply back and say that I gave "yet another window resizer" a try. The result? The same as firesizer!!! It still resizes the whole window and not just the active/viewable area.

I'm sorry, but you are mistaken. YAWR absolutely, positively, unequivocally does not resize the same way firesizer does. If you wish to test this please remove firesizer and then install YAWR so you do not have both of them installed.

I tested both extensions (one at a time) and they produced the same result. To prove is, I did a video screen capture while I tested. Please watch the results here:


The video was very helpful in understanding the problem you are having. This is a misunderstanding of what the "html area" means, which in Firefox means the area below the tab bar and above the status bar.

When you open a sidebar, it encroaches into the area that shows other web pages. That's the way it's supposed to be, and the sidebar counts as part of the "html area". Firesizer resizes what Firefox considers to be the "html area", and this includes any sidebars.

I can understand that you might not agree with this, but that's the way it is nonetheless. If it was not like this, every time you opened or closed a sidebar, Firefox would need to resize the whole window to make it fit. This would be more jarring and much worse for the user experience than what it does right now.

I now consider this issue closed and marked as wontfix/notabug.

Firesizer seems to be visually broken in Firefox 4 beta.

In the latest beta, currently 4.0b6, Firesizer shows transparently and can be difficult to read.

Since there is no release of Firesizer for Firefox 4.0 yet, you must have disabled extension enforcement checking. I'm glad you find Firesizer useful enough to try to force it, but when you break things like that, you get to keep the pieces.

I have been testing Firesizer on the 4.0 betas, and that is a known issue. However, other extensions have the same problem, so it is most likely an issue with Firefox itself. I will continue to check on the betas and will release Firesizer when it's working for that version.