Comment by sasjaws
Thanks for having a look, I actually started out from traditional characters, but once I realized >90% of the students only do simplified I switched.
I also tend to believe to just convert between them is not the best approach. Better to find different content for both. If student wants to learn traditional script, they usualy want content from Taiwan and not from China, and the other way round.
Almost anybody serious about learning Chinese is going to want to read some things written before the 1960s and for those things, people are reading the exact same books, essays, poems, speeches, etc. The simplified versions of all of those works are literally converted from the traditional versions. Ditto for all kinds of popular content that originated in HK, TW and overseas Chinese communities.
There is no long-term gain from storing "hair" and "emit" under the same entry in your database. Storing 髮 and 發 separately, along with 发 as the simplification of both is a small effort now that will constrain you a lot less in the future. I've literally seen this pitfall happen with about 40 different Chinese learning apps over the last 15 years. Only a few (like Du Chinese and Pleco) got it right early on.