Sebastian Blask

About me

Developer Information
Name Sebastian Blask
Location Sweden
Occupation Developer
User since January 15, 2014
Number of add-ons developed 7 add-ons
Average rating of developer's add-ons Rated 4 out of 5 stars

In a little more detail...

I am a developer who's at home in different countries and works and lives in different languages. After switching to Firefox, I started to write add-ons to replicate functionalities that I was used to from Opera. I think I covered the most important ones that were not already implemented by others.

Add-ons I've created

Image Forward Compatible with Firefox 57+

Easy cycling through images and image links on a page. Inspired by parts of Opera 12's fast forward.

Rated 5 out of 5 stars (3)
204 users

Enhanced Image Viewer Compatible with Firefox 57+

Enhances the browser's default image viewer

Rated 5 out of 5 stars (2)
82 users

My Reviews

Don't touch my tabs! (rel=noopener)

Works great! Rated 5 out of 5 stars

It would be even better though if the hostname check could be disabled, just in case. Also, it shouldn't be too hard to get rid of the jquery dependency? Just imagine you've got 20 add-ons and they all load jquery for all pages, that would probably result in quite a slow-down?

Dark Mode (WebExtension)

Rated 3 out of 5 stars

It works well, but usability-wise it's not great. I find the toolbar button rather unintuitive (I understand the logic, but the orange looks like it's on even though it's off) and all the preferences should be available through a popup from the toolbar button, especially the whitelist (shouldn't it be called blacklist), so I can see changes immediately.

This review is for a previous version of the add-on (0.1.7). 

New Tab Override (WebExtension)

Works as it says Rated 5 out of 5 stars

Works as it says. However, looking at the code, I saw that the add-on is not cleaning up properly, so if you deinstall or disable, the previously configured URL is still used when opening a tab. Maybe something to improve? (See for how to do that)

This review is for a previous version of the add-on (1.0). 

Close Button

Rated 5 out of 5 stars

Works great. I am using Linux and have Firefox' title bar disabled to save space, so this is a great way to be able to close it using the mouse.


Rated 5 out of 5 stars

Not slightly, but greatly enhanced view image! All the functionality you can think of accessible through the keyboard. There are other extensions like this, but they do only parts of what this one can do and you have to use the context menu or buttons. Have been looking for something like this for a long time. There are two things that I can think of that could be added:

- the possibility to make the choice of natural size/fit to screen sticky for when you iterate through images (see my Image Forward extension)
- the choices of zoom level for the loupe should include natural size. this would allow quickly seeing details in good quality of large images that have been resized to fit the screen. the current zoom seems to be set based on the resized image and depending on the original image size leads to artifacts/bad quality

EDIT: these two features where added in version 0.9.8 and work great. Thank you very much!

This review is for a previous version of the add-on ( 

Custom Tab Width

Rated 5 out of 5 stars

Worked perfectly before Firefox 29, now it still works, but as Firefox no longer seems to take browser.tabs.tabClipWidth into account, there are no close buttons if the tab width is below 140px(the default), even if usually they are. A workaround for this is to use stylish or userChrome.css to set this:

.tabbrowser-tab .tab-close-button{display: block !important;}

Double Click Add New Tab

Rated 5 out of 5 stars

Does what it says. Unfortunately you still need -moz-bindings in userChrome.css to enable opening of new tabs on click in tabbar(not on a tab). But looking at the code, this seems to be a bug in Firefox and not in this add-on. See on how you can set this up.

This review is for a previous version of the add-on ( 


Rated 2 out of 5 stars

Images are loaded or not loaded depending of the settings which can be changed through preferences, button click or keyboard shortcut. However, it doesn't behave like Opera in that if you have load images as default setting, load the page and then change the setting to not load images, the images are still shown. The other way around it's the same, if you don't load images by default, load the page and then decide you want to see the images, you have to change the setting AND reload the page. If that would be changed, this extension would be great, but like this it's not what I expected.


Rated 5 out of 5 stars

Does it what says and made the mess of text I had readable.

This review is for a previous version of the add-on ( 

Disable CSS

Rated 5 out of 5 stars

Does what it says and is simple to use. A keyboard shortcut would be nice, but the button in the context menu does its job.