A 301 redirect is a rule on your web server that tells browsers and search engines a page has moved for good and where to find it now. When someone opens the old address, they land on the new one without ever seeing the page that used to be there.
Think of it like a change-of-address card at the post office. You move house, you file the card once, and every letter sent to your old address keeps arriving at the new one. A 301 does the same job for a URL: visitors who click an old bookmark and search engines that have the old link in their index both get forwarded automatically. The big difference between this and a 302 redirect is that 301 is permanent, so the new page inherits the ranking the old page had built up.
Where this really matters is during a site relaunch or a URL change. Say you move every blog post from /blog/post-name to /articles/post-name. Without 301s, every old link points at a 404 page and the SEO value you spent years earning evaporates. With them, the move is invisible to your visitors and your rankings carry over.
One practical caveat: avoid long redirect chains. If an old URL points to a second URL that then points to a third, each hop adds delay and leaks a little authority. Always send the old address straight to its final home in a single step. And point each redirect at a page that genuinely matches the old one. Sending every dead URL to your homepage looks tidy, but Google often reads it as a soft 404 and passes none of the old ranking on, so a like-for-like target beats a blanket catch-all every time.
At TopDevs we map every old URL to its new home before a migration goes live, so a redesign never costs a client their traffic.
