I am new to OSM but I have one question. Wouldn’t it be better if all names were put in the native language plus the english version? E.g. I’m going to Iran in summer and as I don’t know the persian alphabet I just don’t understand any name, e.g. Tehran:

The english names are already in our database. The main map just doesn’t show them. See:

You should try another OSM based map, for example:

Apps like Osmand or do also display names in the language which you prefer.

I see, thanks!

The standard is that the primary name should always be that which is used in maps in the country in question. Other than that, people can provide as many alternate language name as they like, although there is a school of thought that says that one should not include a name which is a simple transliteration.

English has no privileged status as a language in OSM, and the degree to which alternative languages are present tends to reflect how internationally famous the place is.

The standard Mapnik layer uses the primary name. The standard maps are there to help people contributing to the map, who will normally be in the country itself, at least if contributing names. If someone commercialises the map for English speakers, they should create their own rendering using English or other Latin alphabet names, when they are available, and should consider transliterating from other scripts.

see also for details …