Word for "software with a large size"?

Solution 1:

You can use bloated as a somewhat loaded term which is also a bit ambiguous: it may indicate software which takes up a lot of disk space, is memory-hungry, and/or works slowly. It may also suggest there are too many features or that they are cumbersome to use.

More technical (and also more specific) terms include: software with a big disk (or memory etc.) footprint and resource-intensive software. On a more generic note, you can say the software is demanding (though without any context, it may not be clear if it's demanding of the computing resources or of the user).

Solution 2:

In a neutral pair of phrases, you could call a piece of software lightweight at one end of the scale and resource intensive at the other end.

From the Reddit thread "Least resource intensive web browsers":

What would be the least hardware intensive web browsers these days? I am currently running Firefox 75.0 (64-bit) which is great in terms of functionality however it is utilizing nearly 1.1 GB of memory which is around 80% of the total memory available on my laptop. I have only three tabs opened one of the being reddit and a few active extensions …

• comodo icedragon is by far the best lightweight browser i’ve ever used on my intel atom processor windows tablet. it has full firefox addon compatibility, themes, syncing (even the open tabs), and built-in adblocker if you don’t want resource intensive addons. it’s responsive and amazingly easy on the ram. i have more than 13 tabs open and active at the same time right now with ublock origin, nano defender and decentraleyes running and it’s taking up around 700mb of ram, which is what chrome uses for 3 tabs.

Resource can be replaced by the specific resource. In the context of this question, it would be disk intensive.

If it's meant in a pejorative sense (meaning that the software's size has made it take up too many resources for too little return), a common expression is bloatware:

From Techopedia:

Bloatware is software that has unnecessary features that use large amounts of memory and RAM. Software comes to be known as bloatware when it becomes so unwieldy that its functionality is drowned out by its useless features. This is also known as software bloat …

Bloatware usually occurs as a result of feature creep. Because software is traditionally redesigned on a yearly basis, many developers feel the need to add additional functionality in order to entice users into upgrading the existing software. Unfortunately, the added features increase the size of the program and the system requirements needed to run it smoothly, eventually forcing the user to upgrade in order to run the latest software.

Solution 3:

Bloatware is a term for a piece of software that is (in the opinion of the speaker) too large. It used to be used a lot for programs like Microsoft Word that showed the user far more features than he would likely ever use, before they learned to hide those options behind user-friendly toolbars.

Resource hog or memory hog might be used for a program which consumes a large part of the system's available resources, especially if this impacts other programs running on the machine. (The word "hog", which literally means "pig", is often used in English to mean something like "glutton".)

Or maybe you mean enterprise software? That term refers to large systems that run on servers and are used by several people throughout an organization; for example an HR system, or a manufacturing planning system. These are indeed very large software systems. If you're talking about an older enterprise system, one that may be written in an old language that is difficult to maintain, but which the organization can't do without, we call that a legacy system. Legacy systems are often monolithic (i.e., all one big piece) which makes them hard to modify.

Solution 4:

Jason Bassford suggested lightweight for one end of the scale; for the other end, I'd suggest the obvious opposite: heavyweight.

That can carry connotations of size (installation, codebase, and/or UI/API), the complexity of what it does, the resources it uses (CPU, memory, storage, and/or servers), cost, level of robustness/redundancy, or even prestige/reputation.

Or you could simply describe a piece of software as big.

That's more specifically about aspects that can be measured, most usually the size of its installation.

And in response to some of the other answers and comments: in standard English ‘software’ is a mass noun (like ‘air’ or ‘bread’): you can talk about some software, or a piece of software, but you can't refer to ‘a software’ (nor to ‘softwares’).  (Even though it might be more convenient to do so!)