Difference between Defect, Error and Bug

In the testing world it is very common that Quality Engineers talk about defects, bugs and errors, during the software development life cycle. For anyone that is not into software development that much, these terms may seem synonyms of each other. Therefore, it becomes useful to understand each of these terms individually.
Let’s talk about the difference between defect, bug and error. In general, we use these terms whenever the system/application acts abnormally. 


Defect is the difference observed between expected behaviour and the actual results which are noted post the event of testing a software, it is all about the current product does not correspond to the customer`s requirements. It differs from a bug in the fact that a defect is found out before the product goes into production.

Example of a defect:

  •  Customer`s requirements wants a landing page with a blue login button on the right corner of the screen.
    Actual result: The login button is on the right side.

In other words, If a developer finds an issue and corrects it by himself in the development phase then it’s called a defect.


In software engineer error can have two definitions: it can be a programming mistake generated due to incorrect loops or wrong syntax, and an error expected from customer`s requirements.error


  • Errors due to configuration such as inadequate storage area for memory. (Error generated by programing mistake).
  • If the user hits login without inform the username and password the system should Display an error message saying the user is missing the mandatory fields. (Error from customer's requirements).


Once the product is completed and it is delivered to the customers and if the customer find any issues in product or software then this condition should be called as a `bug`. People widely say the bug is an informal name for the defect.bugg

In other words, if an end user finds an issue in product then that particular issue is called as bug.


I hope I could help you know a little more about the amazing testing world, remember to share this post with anyone who might benefit from this article, simple terms are the ones that confuses everyone.


Date posted: February 16, 2021

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