Using apache .htaccess to rewrite "/" as ".html" -

to give quick example of i'm after, want:

example.com/folder/about/   

will show me page located at:

example.com/folder/about.html 

currently, .htaccess file looks this:

rewriteengine on rewritebase / rewritecond %{request_filename} !-f rewritecond %{request_filename}.html -f rewriterule ^folder/(.*)$ folder/$1\.html [nc,r=301,l] 

which works when go to:

example.com/folder/about 

but not when go to:

example.com/folder/about/ 

which tries load:

example.com/folder/about.html/ 

which not file or directory.

you can use %{request_filename} variable second time, capturing file name:

rewriteengine on rewritebase /  rewritecond %{request_filename} !-f rewritecond %{request_filename}.html -f #new line rewritecond %{request_filename}.html .*/(.*)/? rewriterule ^folder/ folder/%1 [nc,r=301,l] 

update

put before previous block

rewritecond %{request_filename} !-f rewritecond %{request_filename}.html -f rewriterule ^folder/(.*)/ folder/$1 [nc,r=301,l]