November 9, 2006

What is the difference between Bug, Error and Defect?

Bug : It is found in the development environment before the product is shipped to the respective customer.
Error : It is the Deviation from actual and the expected value.
Defect : It is found in the product itself after it is shipped to the respective customer.

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Blogger lavanya said...

Bug:It is evidence of error in software.A bug is a coding error in a computer program

Defect:Failure in normal function.

Failure:Occurs when faule executes.

Fault:It is result of error.

Error:Represents mistakes made by people.

2:18 PM  
Blogger brainstorm said...

This is what I was looking for yesterday.Wooondoooo job buddy!!!

6:01 PM  
Blogger hemali said...

Bug: Logical deviation- It will not show any error but it
will effect the system. (Ex: Online shopping- Suppose
customer placed the order and got the order conformation
but the details are not saved in DB or not reached the

Defect : Nothing but error it will not effect the system.
It occures due to syntax or exceptions.

6:20 PM  
Blogger mikek said...

Another possible definition
Error deviation from the specs at the stage of development. eg An deviation in the design during the design phase is an error.

Defect is when the error is detected in a latter stage. eg after shipping to the customer or finding an error in the design when you are testing the product.

6:56 AM  
Blogger mohankrishna said...

there is no difference between Bug and a Defect. both are same.
if there is difference according to you...
can u people let me know..what is the difference between BUG tracker and Defect Tracker.

3:14 PM  
Blogger ramireddy said...

Error:Any incorrect home action that producess problem in the sysytem.

Bug : Devation from Expected behaviour to Actual behaviour is called bug.

Email :

11:24 AM  
Anonymous Twinkle said...

I think Hemali is right. A bug is a logical defect in any program while an error may be a syntax or a run time error.

Moreover a program with a bug may run a few times and show strange behavior in some cases while a program with error may not run at any time.

4:51 PM  
Anonymous Nikhita said...

In software testing
Defect:devation from Expected behaviour to Actual behaviour to coding
Bug:After the defect is reported to the development team,the developers will review those defects.If they accept the defect then that defect becomes bug(in terms of development environment).

9:36 AM  
Blogger krishnaveni said...

If a Developer find a problem in coding ,then developer is calling that problem as "ERROR"

If a Tester was detected a problem in s/w then tester is calling that problem as "DEFFECT/ISSUE/FLAW"

If customer was faced any problem in S/w during utilization, than cutomer site people are calling that problem as "BUG"

1:20 AM  
Anonymous Anonymous said...

Hi, I have got the BUG definition as different, from all of you, above. Kindly confir on which is correct one. Is it what client says, or is it what development calls, or found.

4:02 PM  
Anonymous Subhash said...

Difference between defect,error,bug,failure and fault
Error : A discrepancy between a computed, observed, or measured value or condition and the true, specified, or theoretically correct value or condition. See: anomaly, bug, defect, exception, and fault

Failure: The inability of a system or component to perform its required functions within specified performance requirements. See: bug, crash, exception, fault.

Bug: A fault in a program which causes the program to perform in an unintended or unanticipated manner. See: anomaly, defect, error, exception, fault.

Fault: An incorrect step, process, or data definition in a computer program which causes the program to perform in an unintended or unanticipated manner. See: bug, defect, error, exception.

Defect: Mismatch between the requirements.

2:40 PM  
Blogger revathi said...

Defect: Defect is deviation from requirement.

Error: Mistake associated with the program.

Bug: Bug is same as defect but usage wise they differ from each other.

Fault: Deviation from the right way of doing things.

Bug is only used by professionals.
Defect is used by customers as well as professionals.

8:27 AM  
Blogger naru said...

hey nikitha r u nageshwar rao studenr?

11:50 AM  
Blogger koushik mitra said...

All the 3 are any deviation from the actual and expected the expected value. But it matters where it is found. If it is found in the development phase then it is considered as Bug, when it is found in the QA stage it is called as Defect and when it is comes from the users/clients (basically after release) it is known as Error.

7:42 PM  
Anonymous Anonymous said...


11:25 AM  
Anonymous Lavannya said...

if is found at development phase its a bug, at testing phase it is a defect and at user level then it is error.

10:41 AM  
Anonymous Anonymous said...

Hi Guys,

Defect:nothing but a Deviations

Bug:Once tester found a issues in testing end we call it as bug

Error:In programmer point of view during the execution if they found any fault we call it us programatic Error

4:15 PM  
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11:59 PM  
Anonymous Aakash said...

A Developer calls a malfunction, a BUG.
A Customers calls a malfunction a defect.

defect should be least possible present(in the end work product) while intention must be to find as many bugs as possible. If u find lots and lots of bugs defect will be lesser and lesser in the end work product.

When product is delivered bugs are called defects and hence before delivery defect density must be minimised to tending to zero.

Error is abnormal behaviour of a process

5:43 PM  
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Anonymous Venu said...

Error or Fault- A mistake in coding.
Defect- If your application is not working according to the requirement spec, then it is called as defect.
Bug- If the defect is caused by a mistake in coding, then it is called a bug.
A defect may arise because of many factors like setup issues, configuration issues& so on. It may not be because of coding error.
That's why if you see the defect resolution summary sheet, you will find some defects with remarks/coments- " Resolved, but not a bug".
All bugs are defects but all defects are not bugs.
Note: Candidates who are attending Testing job interviews, please don't rely entirely on Nageswara rao Sir's notes of Suresh Sir's notes. They are good, but not enough to get a job. Please read some textbooks written by authors like Srinivasan Desikan, Cem kaner, Software Roger Pressman etc. All the best..

1:49 PM  
Anonymous Bug defect tracking said...

I was thinking these all are same before reading this, now it has been clear that what is the difference basically. Thanks for sharing.

2:22 PM  

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