It is not possible to find a list of all names of fruits online. Lists that can be found online may contain hundreds of names of fruits, but these lists cannot possibly be complete. Scientists estimate that there are hundreds or thousands of different types of fruits, and some are yet to be documented.
Part of the reason why compiling such a list of names of all fruits is difficult is because of different climatic conditions and geographic locations that favor the growth of different types of fruits. Another possible reason is the remoteness of some regions which may hinder scientific studies that are key in the discovery, naming and classification of fruits.
What is found in these lists are names of common fruits that are known by a common name or those that originate from the same geographical location. It is therefore possible that there are more fruits that grow in geographically isolated areas and they have not been discovered or documented yet. Additionally, a fruit may be common in one geographical area and be unknown to people living in a different part of the world.
Of the lists available online, Wikipedia tries to give a comprehensive list of fruits and even categorizes them according to geographical origin, favorable climate, type of flora and by alphabetical order.