This is exactly what I needed to quickly search for vinyl records accross multiple stores and sites. Thanks!

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!

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

Excelente extensão

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 :)

Brilliant app to add a custom search engine. Please note that as of now, you have to have every field filled out when adding a custom search engine.

Excellent!

Not working, I typed "msduck test" and nothing happend.

Edit: It worked, I didn't click "save preferences."

would be nice if you add an option for search suggestions/autocomplete search words

You saved me tons of hours, thanks!

Super useful! I wish firefox had this built-in.

A couple suggestions:
- would it be possible to remove the "ms" prefix? (I suspect this might be a firefox limitation)
- it would be nice to also have a {searchTerm[0]}, {searchTerm[1]} etc syntax. In some cases splitting by word would be very useful.