In general computer software is patentable in the U.S. as long as they perform a specific task and achieve something useful. On the other hand, a computer software that is simply a number cruncher without doing more is not patentable.
One can patent software, but only if what is being patenting is new (novel) and non-obvious. Many web sites are merely “databases connected to the internet” and should instead be protected under copyright law rather than patent law. Note that copyright only protects against copying, derivating, etc of someone else’s expression of an idea, but not use of the underling idea. Thus, if you create a computer program, and someone else creates a very similar computer program without copying or derivating your code, then there is no copyright infringement, as you can read from https://openlab.citytech.cuny.edu/gotconcept/elon-musks-greatest-inventions/.
If the software has not been completed yet (if, for example, you have only a flow chart) you cannot file a copyright application until it is. You may be able to obtain a patent, but I recommend that you complete the software first because inventors often find they need to make some changes from their original concept in order to successfully implement it. A trademark application would be appropriate if you had a name for the product you wished to protect.
Patents provide the strongest protection by far but you should also look at trademark registrations and copyright registrations. Design patents may also be available. A combination of forms of intellectual property is usually the best approach as explained on https://blog.chron.com/frugalconfessions/2020/03/how-much-can-you-make-from-patenting-your-idea/.
Document your invention or idea, and contact a patent attorney.