Is there a memory limit for a single .NET process

32bit or 64bit? 32bit is 2gb (for a process), 64 bit is 1TB (enterprise edition 2003 server).

However, the maximum size of a CLR Object is 2gb even on 64bit.

Update: the information above was correct in 2008. See Ohad's answer for more recent information. Windows 2016 server can have a maximum of 24TB.

I have recently been doing extensive profiling around memory limits in .NET on a 32bit process. We all get bombarded by the idea that we can allocate up to 2.4GB (2^31) in a .NET application but unfortunately this is not true :(. The application process has that much space to use and the operating system does a great job managing it for us, however, .NET itself seems to have its own overhead which accounts for approximately 600-800MB for typical real world applications that push the memory limit. This means that as soon as you allocate an array of integers that takes about 1.4GB, you should expect to see an OutOfMemoryException().

Obviously in 64bit, this limit occurs way later (let's chat in 5 years :)), but the general size of everything in memory also grows (I am finding it's ~1.7 to ~2 times) because of the increased word size.

What I know for sure is that the Virtual Memory idea from the operating system definitely does NOT give you virtually endless allocation space within one process. It is only there so that the full 2.4GB is addressable to all the (many) applications running at one time.

The following table from MSDN is the most precise answer to your query. Note that the IMAGE_FILE_LARGE_ADDRESS_AWARE flag cannot be set directly from the managed compiler, though fortunately it can be set post build via the editbin utility. 4GT refers to the /3gb flag.