mod rewrite directory if file/folder not found

Question

I have a folder named "folder1" in my root directory

www.domain.com/ www.domain.com/folder1

I need to redirect all the requests to www.domain.com that turn up to be a 404 error, to folder1. Like so:

www.domain.com/a_file.txt

If a_file.txt doesn't exist, look in folder1:

www.domain.com/folder1/a_file.txt

I want this to work the same for subdirectories, like so:

www.domain.com/a_folder (redirect if it doesn't exist in the root)

www.domain.com/folder1/a_folder

I know I should use RewriteCond %{REQUEST_FILE} !-f but I can't seem to figure it out.

Solution

RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_URI} !^/folder1/
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule (.*) folder1/$1 [L,R]

• The first rewrite-cond ensures you do not loop (in case the file does not exist inside folder1 either
• The second one checks that target is not a file
• The third - that it is not a folder either
• And, finally, rewrite the url. L flag means this is the last rule applied (even if there are rules after it), R means redirect. You can also add QSA flag if you want any query-string parameters passed to the original be sent to the new url