The Myth of Legacy Programming Languages: Age Doesn't Define ValueThe Myth of Legacy Programming Languages: Age Doesn't Define ValueThe Myth of Legacy Programming Languages: Age Doesn't Define Value
Despite common assumptions, the distinction between "legacy" and "modern" programming languages is subjective.
For software developers , it can be tempting to dismiss a programming language as a poor solution for building new software simply because it is "legacy."
The question, though, is what, exactly, is a legacy language? It's easy to slap the "legacy" label on a programming language based on a variety of considerations. But there is no formal definition of legacy programming languages. In reality, the quality of being legacy or not tends to lie in the eye of the beholder more than anything else.
What Is the Definition of Legacy Programming Language?
A legacy programming language can be defined as one that is outdated or is no longer widely used.
That, at least, is the simple version of what counts as a legacy language. The definition becomes more complex when you consider that terms like "outdated" and "widely used" are subjective. A language that one coder considers obsolete may remain a favorite of another.
Legacy vs. Modern Languages: Key Considerations
Instead of trying to define legacy languages based on one or two subjective criteria, a better approach is to consider the wide range of factors that may make a language count as legacy or not. Here's a look at key characteristics that may distinguish legacy programming languages from modern ones.
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1. Age
The most straightforward, but also crudest, way to define legacy languages is based on their age. Languages that were introduced decades ago are sometimes considered legacy simply because they're old.
The problem here, of course, is that many decades-old languages are still in widespread use. C dates to the early 1970s, but there remain plenty of reasons to learn and use C a half-century after its debut. C++, another popular language that few people would call legacy, is only slightly younger than C. And Python , the world's most popular programming language by many measures, will soon turn 35, making it older than many other widely used languages, such as Java and Go.
On the other hand, some languages that most developers would likely place firmly in the legacy category, such as FORTRAN and COBOL, are among the earliest languages created — so in those cases, age does correlate with legacy status (although it's important to note that languages like FORTRAN and COBOL are still certainly being used ).
2. Development status
Languages may be considered legacy when no one is still actively developing them — meaning the language standards cease receiving updates, often along with complementary resources like libraries and compilers. This seems reasonable because when a language ceases to be actively maintained, it may stop working with modern hardware platforms.
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But here again, it turns out that not all languages fall off the map when active development on them ceases. For example, Lisp, whose most recent standard release dates to 1994, remains the 21st most popular language, according to the TIOBE Index . (TIOBE lists LISP-related languages, like Clojure, separately, so the fact that LISP dialects are still being developed does not appear to explain the continued use of LISP itself.)
chart of top 25 programming languages August 2025
Languages may become less popular when active development ceases, but deeming them "legacy" based on development status alone may be narrow-sighted.
3. Popularity
Distinguishing between legacy and modern languages based on their popularity may also seem reasonable. After all, if few coders are still using a language, doesn't that make it legacy?
Maybe, but there are a couple of complications to consider. One is that measuring the popularity of programming languages in a highly accurate way is impossible — so just because one authority deems a language to be unpopular doesn't necessarily mean developers hate it.
The other challenge is that when a language becomes unpopular, it tends to mean that developers no longer prefer it for writing new applications. But that doesn't mean existing applications written in the language are going away. For instance, consider PHP, a language that more than a few people have deemed to be "dead" — but which remains the main language for some of the largest websites and software platforms, such as Facebook, Wikipedia, and WordPress. If PHP is a legacy language, no one told the programmers who maintain these platforms.
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4. Association with legacy technology
Legacy technology is a generic term that can refer to any type of platform or tool (including but not limited to programming languages) that IT professionals no longer consider optimal or desirable. On-prem infrastructure and monolithic applications are examples of what at least some folks would call legacy technology.
Programming languages sometimes end up in the "legacy" bin when they are associated with other forms of legacy technology — or when they lack associations with more "modern" technologies.
For example, Go, whose concurrency features make it a good fit for microservices development, is often considered "modern" (it helps that the language is less than 20 years old). But C, which tends to play a less prominent role in today's web-based world than it did when most software ran on-prem, is easier to dismiss as a legacy language, even though it remains very popular.
Conclusion: Legacy Is in the Eye of the Beholder
In short, there is no definitive way to decide what counts as a legacy language and what makes a language modern. Some languages may certainly have a more legacy "feel" than others, but that hardly means they're obsolete, or that they are not worth learning.
So, before tossing around the "legacy" term with abandon, developers should perhaps consider what it really means and whether any languages hold true legacy status.
About the Author
Technology analyst, Fixate.IO
Christopher Tozzi is a technology analyst with subject matter expertise in cloud computing, application development, open source software, virtualization, containers and more. He also lectures at a major university in the Albany, New York, area. His book, "For Fun and Profit: A History of the Free and Open Source Software Revolution ," was published by MIT Press.
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