What an interpreter is
An interpreter is a program that takes source code written by a programmer and runs it directly, translating and executing it one piece at a time. Rather than converting the entire program into machine code ahead of time, it works through the code as the program runs, figuring out and carrying out each instruction on the spot. Many popular languages, such as Python and JavaScript, are traditionally run this way.
How it works
When you run a program through an interpreter, the interpreter reads the source code, works out what the first instruction means, and immediately carries it out, then moves on to the next. It repeats this process line by line until the program finishes or hits an error. Because it handles the code as it goes, there is no separate step that produces a standalone file of machine code in advance.
Interpreter versus compiler
The usual comparison is with a compiler, which translates the whole program into machine code before it runs, producing a file the computer can execute on its own. An interpreter instead translates and runs at the same time, every time the program is used. Compiled programs tend to run faster, while interpreted ones are often easier to develop and test, since you can run code immediately without a separate build step.
Advantages of interpreting
Interpreters make programming more flexible and immediate. You can write a line of code and run it at once to see what happens, which is excellent for learning, experimenting, and quick fixes. Interpreted languages are also typically easier to move between different kinds of computers, since the same source code can run anywhere the interpreter exists, without needing to be recompiled for each type of machine.
The trade-offs
The main drawback of interpreting is speed. Because the code is translated every time it runs, an interpreted program is generally slower than an equivalent compiled one. In practice, many modern systems blur the line, using clever techniques that compile parts of the code while running to get the best of both worlds. Still, the basic idea of an interpreter, running code as it reads it, remains central to how many languages work.
The bottom line
An interpreter is a program that runs source code directly, translating and executing it line by line rather than converting it all in advance like a compiler. This makes development immediate and flexible at some cost to speed, which is why interpreted languages are popular for learning and rapid work. Understanding it explains how languages like Python and JavaScript turn written code into action.
Related on Skillo
See also: What is a compiler? Explained, What is JavaScript? Explained.
Sources
Published date reflects the original event date (2026-10-23). This article is original Skillo editorial written from the sources above; facts were verified in September 2026.
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