Synonyms of 'extant'
The oldest extant copy is dated 1492.
usage note:Used carefully, the word extant describes something that has survived, often against all odds. It therefore carries a slightly more specific meaning than in existence, and should not be considered as being automatically interchangeable with this phrase. For example, you might say the oldest extant document dates from 1492; but in existence (not extant) for 15 years, they are still one of the most successful bands in the world. In many contexts, however, these ideas overlap, leaving the writer to decide whether extant or in existence best expresses the intended meaning.
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You can describe something as existent when it exists.
human rights in former and still existent communist states
Existing is used to describe something which is now present, available, or in operation, especially when you are contrasting it with something which is planned for the future.
the need to improve existing products
Thesaurus for extant from the Collins English Thesaurus
If something is extant , it is still in existence, in spite of being very old .