Nice to meet you.
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初めまして or 始めまして？
When checking translations, you'll find both to give a translation of "How do you do?". So which do you choose to use when writing it?
初め = first
始め = beginning, start, launch
A tip to understanding the difference between these is to focus on the meaning of the kanji: "first" versus "start".
When you first meet someone, you say "How do you do?". This is very different from starting a new project.
初めまして → Nice to meet you.
始めまして → I'm starting.
