There's a few things going wrong here. First, there's no certification on the U.S. theatrical release. You can see that here. I just added the R rating so that is now correct.

Second, it doesn't look like certification supports the pipe or comma separated values right now. It's a one value at a time query. You could change your query to this which will get you 90% the way there:

https://api.themoviedb.org/3/discover/movie?api_key=###&language=en-US&region=US&sort_by=popularity.desc&certification_country=US&certification.lte=PG&include_adult=false&include_video=false&page=1

For the US, certification.lte=PG will include PG, G and NR.

But in order for you to do explicit certification filtering, I need to add support for the pipe and comma notation to certification.

For the US, certification.lte=PG will include PG, G and NR.

or make NR not come back unless specified :D If you specifying a rating, you probably don't want unrated films anyway.

Thanks for the Query - i'll see what i can do to use it.

PS: Awesome site, love it.

I think the best way to get what you want would be to add AND and OR support to the certification filter. That's the best way to solve it.

Edit actually, completing this ticket would solve it too. This is the better way.

PS: Awesome site, love it.

Thanks!

That sounds stupendous! Should I just keep an eye on the discover API page for the change or bookmark the ticket and check it every now and again ?

I've updated the ticket with a link to this post, I'll update this post once it's done.