A .htaccess file is a per-directory configuration file used by the Apache web server. The name starts with a dot because it is hidden by default, and Apache reads it on every request to decide how to handle the files in that folder. It is plain text, so you can open and edit it in any code editor.
Think of it as a set of house rules posted at the entrance of a room. Anyone who walks in has to follow them. A line like Redirect 301 /old-page /new-page tells the server to send every visitor of the old address to the new one, which is exactly how you keep links working after you rename a page. People also use .htaccess for custom 404 screens, password protection, blocking unwanted bots and forcing every visitor onto HTTPS. The rules cascade, too: a file in your root folder applies to everything below it, and a second one deeper in the tree can override those rules for just that part. So you might force HTTPS site-wide at the top, then add a password prompt on a single staging folder lower down.
Because the file is checked on every single request, a tiny typo can throw a 500 error and break the entire site, not just one page. That is also why it is mostly an Apache thing. If your host runs HTTP through Nginx or a serverless platform, the same rules live somewhere else entirely. Nginx uses its own server blocks, and a platform like Vercel uses a config file in your project. For redirects in particular, a 301 redirect defined here is a common and reliable approach, and it is the first thing to reach for when an old URL needs to keep sending people to the right place.
At TopDevs we keep .htaccess rules tidy and version-controlled, so a quick redirect change never turns into an afternoon of downtime.
