After trying many resizers for Firefox, this is by far the simplest to use and the most flexible to configure.

This one is finally to work! I try 4 extension and no of them can work.

Only working half-way, at best!
No matter the actual window size, if whether maximized or not, this add-on always detects and displays a window size of 632x119, and offers to use that – and only that size for a new resolution to save. Of course, the result is an unusably minute letter box size browser window without any page content visible.

I suspect the add-on's inability to detect the correct window sizes stems from the browser's protection against fingerprinting. However, other similar add-ons don't have this problem with identical Firefox settings, so this is a no-go for me with this WindowSizer add-on.

The setting of the window size itself might work, though. I didn't really take the time to measure whether the resulting window really had the 632x119 pixels. ;)

There are a couple of extensions like this out there, but this one was the only one that I could (easily) figure out how to save current window size as preset.
Crucial for streaming.

Heart-broken and disappointed, Dr. Cheap ... Had high hopes ... Wanted to give ONE MILLION STARS, but I can't set the font size ... [edited -- no, more, the magnification / resolution of the page ... or, would it be scaled scaling, not sure]. I so hoped that I could set a Profile on this where I can read my Google Mail in the 120% size of a window at 1920 x 1080. But, there is no place here to select font size. If that would have been here, I'd have let my wife carry your babies ... {Grin} ... But, please, add that feature and I'll give you 100,000 reviews. Maybe, even add URL to that list where you can have a checkbox that will auto-change window when visiting that URL. That's an idea too.

Please, please, please ... keep improving this extension. It has great potential. But, right now, is useless for me, and I don't see the purpose really of it now in current state ...

Okay, I found this extension, "Zoom Page WE", and I think that is more what I needed. Maybe, I didn't understand clear purpose of this extension. Because I need that ZPWE. Okay, I'm going to raise my rating from 2-stars to 3-stars. But, still, please, consider the suggestions that I made.

Setting any other resolution but 632x100, which is listed as current window size (it definitely is not) results in an error, stating: "Please correct errors" while marking the two fields red, emptying them.

The hotkey to use this ridiculous preset work, so have a second star. Am willing to provide more information if needed.

The hotkeys make the extension unusable on mac. The Alt+2 hotkey is already used for the @-symbol for instance.

It shall support big resolutions like 4K UHD, too.

LOVE IT :D
Wish I could extract the settings though :D :D :D *hint* :p

Position do not works on Windows 7. Sometime there is a bug refresh when you click on the icon extension (the menu is empty). You can find a better extension to do the same thing.

Very good complement.
I can configure all resolutions I want and save it.

すばらしい！　欲しかったのコレです。
良設計だと思います：シンプルインターフェイスでわかりやすい
星マイナス１の理由：使って未だ１０分しか経ってないので… すみません…

great! This is what I was looking for.
I suppose this extention is good design: simple interface and easy to understand.
Reason about score of minus 1point star: I have used it only 10 minutes yet... sorry...

It's very useful add-on for me. The only flaw is I cannot 1600 x 1045 for my ultra-wide LG displayer (resolution 2560 x 1080), I have to add 1600 x 1040 instead of. It's appreciated to have 1060 x 1045 in the updated version :)

Save browser Window Size and restore.
This function is the best ,but For me Something missing
That's right, save and restore the window position!

Function Insert about save browser position ,restore one.
That function Insert this add-on
I create this add-on Name:WinSizeNPosition

Please use my add-on, too

I'd like to put 5 stars, as it's rare that an add-on only asks for the data it needs. In this case, none. But I cannot set a custom size, I always get the red "Please correct errors" message without any more explanation.

This extension works well, easy to set up.
It allows to set desired window sizes.

to developer:
1. Thank you.
2. Current window size is show only in preferences, it would be way better if it's shown in the drop-down.
3. Naming is great, it would be better if blank name was allowed.

Very good add-on. Would be absolutely perfect if you could display / determine your current window size. As a web designer I often need to know the exact size of the window to add media queries.

I was looking for an equivalent Firefox extension to Chrome's "Window Resizer" that I use for web development. After some search, this one seems the best alternative. It works very good.
Feature suggestion: Custom default presets for common monitor and mobile resolutions would be a great addition and would make your extension stand out from the crowd.

Works exactly as described, with the ability to make custom resolutions, reorder them as you wish, and with two clicks you can resize your window to your preference!

Wish I could give more than 5 stars. Well done.

My evaluation is 5 if I can save the current window size.

January 2, 2018 Addendum:
Since it became possible to set the current window size at Ver 0.6.1, I changed it from star 4 to star 5.

simple and useful

Very nice & useful add-on! Thank you

I've created two window sizes that provide the best aspect ratio for my most used applications, a news paper and weather site. Everything worked as expected. It would be nice to have an edit feature. Currently the add-on can only Add and Remove. Looking forward to improvement(s) in this app.

Increased to 5 star since the app now gives "edit" capability. Also, there is a new feature that allows you to resize the window and select, name and save the current size. Nice feature! Thanks for the good work.