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Another filter I think is very important: only courses that have video lectures.

I like the minimalism. Filtering is great, but more valuable when you know exactly what you want. That said, a (very) few filters for the most common reasons a searcher knows that they require would probably be helpful. Maybe start with just a free/paid filter?

Another filter: language. Many people don't speak English. Maybe you can automatically detect the language and add to your list of languages as you go?