I recently received a question about how to do multi-select refiners in SharePoint 2013 as comment on my post Limiting Search Results in SharePoint.
Fortunately this is very easy, which is was not in SharePoint 2010.
- On your search page, edit the Refinement web part
- Click the “Choose Refiners” button
- Select your refiner, eg. FileType
- Chose the “Multi-value Refinement Item” display template
- Click OK and Save the web part changes
Your Result type refiner will now look like the image below where you can check off each value you want to refine on.
You should note that when using this template it will in the case of file types show the extension and not the application names which is does with the “Refinement Item” display template. But that’s fixable if you edit your display templates :) and left as an option for you.