N'a pas fonctionné : Firefox 84.0.1 Windows

Awesome. I initially didn't understood well how it worked, but the developer was really helpful, so I'll clarify my misunderstandings here for others in similar situation so that your simple searches work:
1.- You don't have to mingle with search preferences in Firefox.
2. Consequently, you won't prefix regular searches with non default search engines with "@" when doing - as you do in other explorers and FF defaults.
3. You do have to prefix these custom searches with "ms" before the keys added while doing the search. "ms" stands for Multi Search, but you have to use it even for a simple (non multiple) search. Think of ms as "My Search" if that helps fixing what you're really doing in your head.
4. What a real Multi Search (with several keys) does is opening multiple tabs, one for each search engine that you included as the key.

I mostly wanted to alternate searches, rather than doing multisearches at the same time (but will explore that in the future). If you want to search for only the last 3 years for example, which you can do in Chromium browsers with
https://www.google.com/webhp?tbs=qdr:y3

, you can do it in FF with this extension, as clarified by Ravi, the developer with:

https://www.google.com/search?q={searchTerms}&tbs=qdr:y3

You can substitute y with m, d... for months, days... and of course use the number you want.

Still don't know how to do this with ecosia or duck duck go. If anyone knows, please share it so that we all know too :)

Thanks a lot to Kevin for this so needed extension!

you dont need an extension for that. just right click any search field

I miss this SO much on Pale Moon. Any chance you make this possible?

perfect

Category searching not work by the way
ms @Gic test
It seams the uppercase does not support by this plugin



but you should see this fast search options
http://mingyi.org/FastestSearch/1stinstall.html

Absolutely not clear as to how to use this extension. No icon, no options sections in the settings, no nothing.

not sure how to add it to the search bar where all the search icons are at (about:preferences#search)

+ Settings are clear and easy to modify.
- something needs to be done for the amout of tabs that a single command line opens. lets say I translate 5 words in a row a 5 engines, thats 25 tabs opened just like that. There is an addon Translation Comparison that has the multi-column view, so, in total youd have one window/popup but several search engines. or any other simpler trick might do as well.

Works great, but keeps focus after pressing ⏎. What can I do about it? It's rather annoying in web apps, which use keyboard shortcuts, because I have to type ⇥ and then the shortcut.

Excelente extensão

Thanks a lot of this addon.. Have been dying for this one to be present in firefox to move away from chrome. I have around 50-60 such custom search urls and this is a saviour!!

Like everybody says, hate typing ms everytime. Is it possible to customize these 2 chars also? Is it possible to reduce it to one letter and/or allow it to be customizable?

Update: https://superuser.com/a/7374/364519 - Found that all you need to do to have similar custom search urls for firefox, is to create bookmarks with %s in the place - just like in chrome!!! Would be great if this is called out in the addon, as i have been longing for the same to switch to firefox.

Thanks for this addon!

I have small request if possible. I am using this app for searching car parts in many shops with multi search.
It is possible to add keyword 'all' for searchng in all defined engines? for example:
ms shop1,shop2,shop3 keyword - now I use this
ms all keyword - that would be better when using lot of search engines in multi-search mode

One more suggestion - for sure harder to make:) It is possible add column "category" to search engine definition.
sample use:
ms tires keyword - searching in multiple search engines that have in category column 'tires'
ms bearing keyword - searching in multiple search engines that have in category column 'bearings'

EDIT:
Thanks !!!
Now this add-on suits all my needs in searching web ;)
Everything working as described.

Works as expected! Thank you for adding this critical feature back to Firefox :)