WordPress is a free and open source blogging tool and a content management system that offers a hosted and self-hosted solutions.
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Pro Open source
Anyone can view the code of WordPress.
Pro Complete control if needed
If you set up WP on your own server, you can change every single aspect of it as you see fit.
Pro Widely used
According to some statistics, WP powers a fifth of the Internet. It means there are resources for everything. Community support, tutorials, extensions and a plethora of customization options.
Pro Self-host & WP-host options
For free WordPress can be hosted by yourself on your own server, or as a subdomain of wordpress.com. You can also pay to use a custom domain with WP hosting.
Pro Post-level privacy controls
Each post can have a different access level.
Pro RSS feeds for everything
Including tags and categories.
Con A bit of bloat and complexity
WP has grown past being just a blogging platform and as such it's not as lightweight as it used to be. It also considerably more complex due to many more customization options compared to other solutions.
The code is a mess, uses dated conventions and relies on dated technology.