Currently I'm designing a form wizard which will be use in the website. My reason for not putting the button on the form is because I want the user to never press back and so must finish the form.
My question is should I put a back button on my form wizard? Is the back button really important on the form wizard?
The key is to provide the ability to step back, but not encourage it. If it's over-emphasized, some people will feel compelled to review their work regardless.
The example above shows a wizard that allows stepping back either through the progress indicator (click a number) or a subtle back link.
Decision anxiety is a real thing, however small it might be in a given context. In a wizard, you're asking a person to commit to each step along the way. As people decide to submit their answers and proceed to the next form, some percentage will experience uncertainty about the preceding responses or about current responses in relation to them.
At this point, you must provide a way to step back and review or you risk abandonment. At the very least, that person will be unsatisfied with the process and have some distaste toward the experience.
The back button is important. Users should be able to correct any mistakes and review what they have already entered. Also, I do not find the back button a reason users will not finish the form, on the contrary the back button will give them a sense of control and safety.
Considering something like a survey, I might want to move information betweens answer (or copy it). If I can't, I'm quite likely to think that the whole thing is a waste of time, and give up. Stopping the user from going back may have the opposite effect to what you want Similarly if the browser back button breaks anything, they're probably not finishing whatever your wizard is for.
If it's something the user really wants/needs to do (e.g. compulsory trainign), anything you do to try to force them not to go back will only lead to frustration. If it's something like a job application they will need the ability to edit answers in the light of further questions -- they may have given their best example of leadership as an example of time management, and need to swap those answers.
If you can't go back, and you can't cancel or save, then you leave your users with no choice but to close the browser if they really want to back out of the process.
Ideally you should never force the user to find a way to try and do what they want to do, and instead you should try to accommodate or anticipate their needs.
Having said that, if you make your forms short and simple then it is likely that the user will complete it quickly and on the first attempt. That's the best way to make sure that the users don't have to go back.
history.pushState()function which you can use to add 'virtual' pages to the browser's history stack to represent each page of your form.