The key to success is 'to work hard'/'working hard'.

[tulipflower]

Can we use both 'to+infinitive' and 'gerund' after 'to be' verbs?

The key to success is 'to work hard'/'working hard'.

 

[tedmc]

I prefer using the gerund since, logically, "success is something" rather than " success is to do something."

 

[5jj]

It's the key (to success) is ... not success is ... .

I think both forms work.

 

[Tdol]

They both work for me too. You could also use hard work.

 

[Tarheel]

One of the keys to success is hard work. Another is good planning.

 

[Tdol]

You can add luck to the list.