digikey, mouser, and arrow are the big ones that I'm aware of. All of their UX is really bad compared to McMaster though.
I love when a field value table has redundant values for 20mm, 2cm, 2.0cm, 20mm with a trailing space, etc. A lot of the value-add here from McMaster comes from pure data cleanup and categorization and cleaning up the categories and fields. That gets way harder to do on something the size of mouser or digikey though, they have a LOT of product types in the catalog, and tens of millions of products in their warehouses. Just cataloging it all is a massive amount of work.
I'd actually be curious what the data structure of the McMaster catalog is to support that. It's a cool website, it makes it seem so effortless to search for parts.
Digi-key definitely could sanitize/normalize their field values better. But I feel they are intentionally being conservative about touching datasheet values given by the vendors.
In practice (based on experience of selecting electronic components), I don't find this a big issue; after filtering on some other obvious, more binary fields, what left is often a small enough pool of values (like 16V, 16.0V, 12-20V, etc.) to be manually selected/checked.
https://tme.eu does a better job of this. If you enter "16V", it knows to also select the 12-20V ranges. It also works the other way around, you can enter "10-22u" in the parameteric search and it will find both 10uF and 22uF parts.
So annoying that digikey doesn't do this, you have to click each value/range separately.
I love when a field value table has redundant values for 20mm, 2cm, 2.0cm, 20mm with a trailing space, etc. A lot of the value-add here from McMaster comes from pure data cleanup and categorization and cleaning up the categories and fields. That gets way harder to do on something the size of mouser or digikey though, they have a LOT of product types in the catalog, and tens of millions of products in their warehouses. Just cataloging it all is a massive amount of work.
I'd actually be curious what the data structure of the McMaster catalog is to support that. It's a cool website, it makes it seem so effortless to search for parts.