404s aren't inherently bad for SEO. Google expects them and won't penalise a site for having 404s on URLs that should be gone. The problems are indirect: a broken internal link wastes user trust and crawl budget, and losing a page that had valuable backlinks throws away that authority.
The decision is intent-based. If a page moved, use a 301 redirect to the closest relevant page to preserve its value. If it's permanently gone with no replacement, a 404 (or 410 Gone) is honest and correct — don't redirect everything to the homepage, which Google treats as a soft 404.
A helpful custom 404 page — with search and links to popular sections — keeps users on site when they hit a dead end. Monitor 404s in Search Console to catch broken links and lost pages worth recovering.
FAQ
Frequently asked questions
Not directly. Google expects some 404s and doesn't penalise them. The harm is indirect: broken internal links waste crawl budget and frustrate users, and 404-ing a page that had backlinks discards that authority. Redirect moved pages; 404 pages that are truly gone.