English isn’t the only language in the world
If you’re running a conference in multiple languages or in a place where fluency level varies, consider offering more than just English.
A lot of conferences in the tech industry are conducted solely in English, even if they’re hosted in a country where English isn’t the first (or second or third) language. This can lock out people whose English isn’t good enough to follow a day of conference talks.
I’ve never seen this directly (I’ve yet to go to a conference outside the UK), but I’ve heard of conferences tackling this in at least two ways:
Run talks in multiple languages. I’ve heard of conferences in Germany that have an English track and a German track, and I’m sure it must happen in other countries.
Provide live translation of talks. You can hire translators who provide a real-time translation of the talks, which people can listen to in headphones. This almost certainly requires more infrastructure, but it’s nice to think about. If you’re doing this, you might want to consider captioning in multiple languages as well.
As with live captioning, it’s helpful to provide the interpreters with a list of specialist/technical terms in advance.