Every file and folder that exists on your web server has a set of attributions, or permissions, that you can change using FileZilla. These permissions are assigned and tells the web server three things about the folder or file. On a very simplistic level, these permissions include
Read: Determines whether the file/folder is readable by the web server
Write: Determines whether the file/folder is writeable by the web server
Execute: Determines whether the file/folder is executable by the web server
Each set of permissions has a numerical code assigned it, identifying what type of permissions are assigned to that file or folder. There are a lot of them, but here are the most common ones that you run into and deal with when running a WordPress website:
644: Files with permissions set to 644 are readable by everyone and writeable only by the file/folder owner.
755: Files with permissions set to 755 are readable and executable by everyone, but only writeable by the file/folder owner.
777: Files with permissions set to 777 are readable, writeable, and executable by everyone. Don’t use this set of permissions, for security reasons, on your web server unless absolutely necessary.
Typically, folders and files within your web server have already been assigned permissions of either 644 or 755. You usually see PHP files with permissions set to 644 if the web server is configured to use PHP Safe Mode.
In case you need to dig further into file permissions, here’s a great reference on file permissions from Elated.
You may run across a situation in which you’re asked to edit and change the file permissions on a particular file on your web server. With WordPress sites, this usually happens when dealing with plugins or theme files. This practice is also referred to as CHMOD, or Change Mode. When someone says, “You need to CHMOD that file to 755,” you’ll know what she’s talking about.
Here are some quick and easy steps for using your FTP program to CHMOD a file, or edit its permissions on your web server:
Connect your FTP client to your web server and then locate the file you want to CHMOD.
In FileZilla, right-click the file on your web server and choose File Permissions to open the file attributes.
Your FTP client may use different terminology.
The Change File Attributes dialog box opens.
Type the correct number in the Numeric Value text field.
This is the number assigned to the permissions you want to give the file. Most often, you’re given directions by the plugin or theme developer on which permissions number to assign to the file or folder, and typically, it’s either 644 or 755. You see the permissions are assigned with 755.
The file saves with the new permissions assigned.