301 Redirects: Merging Pages, Changing URLs, and Passing Authority
1. The difference between 301 and 302: why you can’t get it wrong
301 and 302 are both HTTP redirect status codes, but they mean completely different things. 301 is “moved permanently”: it tells Google the page has moved to a new address for good, the old URL should no longer be crawled, and authority passes to the new URL. 302 is “moved temporarily”: it tells Google the page has moved elsewhere for now and will come back, no authority passes, and Google keeps treating the old URL as the main one.
What happens if you get it wrong: if you want a permanent move but your server is configured to send a 302, Google will not pass the old URL’s authority to the new URL, and your new page has to build rankings from scratch. Worse, Google may keep indexing the old URL, so both versions show up in the SERP and compete with each other.
| Status code | Meaning | Authority flow | Google’s indexing behavior | Use cases |
|---|---|---|---|---|
| 301 | Moved permanently | About 90% passes to the new URL | Indexes the new URL and gradually forgets the old one | Merging pages, redesigns, domain changes, URL changes |
| 302 | Moved temporarily | No authority passes; it stays with the old URL | Keeps indexing the old URL | A/B tests, temporary maintenance, geo redirects |
| 307 | Temporary (HTTP/1.1) | Same as 302: no authority passes | Same as 302 | Same as 302, for POST requests |
| 410 | Permanently deleted | No authority passes; Google removes it from the index quickly | Removed faster than a 404 | Pages you’re sure will never come back |
| 404 | Not found | No authority passes; Google keeps it for a while | Gradually removed from the index | Pages you’re not sure will come back |
How do you confirm you’re using a 301 and not a 302? Check the HTTP response headers in your browser’s Network tab or with curl -I. The Location field should be the new URL, and the status code must be 301. Many CMS plugins default to 302, so you have to change it to 301 manually.Google SEO Other modules: 301 is Site rebuilds and domain changes core tool, and also keyword cannibalization a way to merge pages.
2. Scenario 1: Page Merging and Keyword Cannibalization
Two pages competing for the same keyword is a common problem on B2B sites. Both pages target “CNC machining service,” and neither ranks well—Google doesn’t know which one to put first, so both hover between positions 10 and 20. The right move is to merge them into one page.
| Steps | Action | Judgment criteria |
|---|---|---|
| 1. Diagnose cannibalization | Check Search Console to see which two pages compete for the same keyword | Both pages rank between positions 5 and 20 |
| 2. Pick the page to keep | Choose the one with more complete content, more backlinks, and better rankings | 30%+ more backlinks or 5+ positions higher |
| 3. Merge content | Add the best content from the merged page to the page you keep | Kept page grows by 30% to 50% in word count |
| 4. Set up 301 | 301 the merged page to the kept page | One-to-one, not to the homepage |
| 5. Update internal links | Point internal links that went to the merged page to the kept page instead | Avoid 301 chains |
| 6. Monitor results | Check ranking changes for the kept page after 4 to 8 weeks | A rise of 3 to 10 positions is normal |
Example: An industrial site has two articles on “aluminum extrusion tolerance”: an 800-word blog post and a 2,000-word technical guide. The blog post has 3 backlinks; the technical guide has 12. On Google, they rank 14th and 18th respectively. The fix: merge the blog post’s unique content (a tolerance comparison table) into the technical guide, and 301 the blog post to the technical guide. Also update the 5 internal links that pointed to the blog post to point to the technical guide instead. Six weeks later, the technical guide ranks 6th.
Here’s the counterintuitive part: many people assume you can just delete the weaker page. Wrong. Deleting it creates a 404, and all the backlink authority and historical ranking signals that page accumulated are wasted. The right approach is a 301 to the kept page, passing along 90% of the authority. At the same time, merge the best content so the kept page is stronger than both original pages combined.Merging decisions for keyword cannibalization has more detailed criteria.
3. Scenario 2: URL Changes and Site Migration
Redesigns, domain changes, and URL structure changes all break old URLs. Without 301s, all the backlink authority, historical rankings, and user bookmarks on the old URLs are lost, and the new URLs start from zero. The right approach is to build a complete one-to-one mapping table, with each old URL pointing to a new one.
| Migration type | Mapping method | What to watch for | Authority transfer period |
|---|---|---|---|
| Change URL structure (same domain) | Old path → new path, one-to-one | Launch 301s immediately after the change | 2 to 4 weeks |
| Change domain (same site) | Old domain old path → new domain new path | Keep the old domain for 12 to 18 months | 1 to 3 months |
| HTTPS migration | http:// → https://, one-to-one | Site-wide consistency, don’t mix protocols | 1 to 2 weeks |
| Directory consolidation | Every page on the old site → its counterpart on the new site | Don’t 301 everything to the new homepage | 2 to 4 weeks |
Example 2: A B2B site moves from dated archive URLs like /blog/2026/09/article-slug/ to /blog/article-slug/. During the migration they built a mapping table: every post under /blog/2026/09/ 301s to the matching slug under /blog/. They also updated the XML sitemap, submitted the new sitemap in GSC, and used the Change of Address tool to tell Google the URL structure had changed. Three weeks later, the GSC coverage report showed old URLs gradually dropping out of the index while new URLs gradually rose, with no noticeable ranking swings.
Three hard rules here. First, no 301 chains: old URL 301s to an intermediate page, which 301s again to the new URL. Every extra hop loses 10% to 20% of the link equity. The old URL must 301 straight to the final destination. Second, don’t 301 the whole site to the homepage: sending an old product page to the new homepage wastes all the backlink equity that product page built up on the homepage, and the new product page gets none of it. Third, don’t use a 302 instead of a 301: a temporary redirect passes no equity, and Google keeps indexing the old URL.
4. A 301 isn’t permanent: how long to keep it and when to remove it
Here’s the counterintuitive part: Google confirmed back in 2016 that the equity passed by a 301 redirect isn’t permanent. After a while, usually 12 to 18 months, Google gradually “forgets” the 301, the backlink equity on the old URL starts to decay, and the new URL has to earn its rankings on its own. That means relying on a 301 long term isn’t a strategy.
| Timeline | What Google does | What you should do |
|---|---|---|
| 1 to 4 weeks after launch | Google finds the 301 and starts passing equity | Manually submit important new URLs with the URL Inspection tool |
| 1 to 3 months | Main equity-passing period; rankings shift over gradually | Monitor GSC coverage and ranking changes |
| 3 to 12 months | Equity transfer stabilizes; the new URL builds its own backlinks | Keep building backlinks and internal links to the new URL |
| 12–18 months | Google starts “forgetting” the 301; equity transfer decays | Make sure the new URL already has enough backlinks of its own |
| After 18 months | The old URL’s equity is essentially gone | You can start removing the 301 (carefully) |
Why can’t you remove the 301 right away? Because users still have old bookmarks, linking sites haven’t updated, and Google is still discovering the new URL through the 301. Remove it now and all those visits become 404s. The right approach is to keep it for 12 to 18 months while you keep building backlinks and internal links to the new URL, so it builds up enough equity on its own.
To check whether a 301 is working: visit the old URL in a browser; it should redirect automatically to the new URL, which appears in the address bar. Run curl -I to see the response headers; the status code must be 301 and Location must be the new URL. Enter the old URL in the GSC URL Inspection tool; it should say “Page has been redirected” and point to the new URL.XML Sitemap Update it to the new URLs and remove the old URLs from the sitemap.robots.txt configuration You can’t stop Google from crawling the old domain. It needs to fetch the old pages to see the 301 directive.
FAQ
What’s the difference between a 301 and a 302, and when should I use each?
Two pages compete for the same keyword. When I merge them, which one do I keep?
How much authority does a 301 redirect pass?
How long should I keep a 301 in place, and when can I remove it?
After a redesign, can I just 301 all the old URLs to the homepage?
How do I confirm my 301 setup is working?
Final thoughts
A 301 redirect is one of the most delicate operations in SEO: get it right and authority transfers smoothly and rankings hold; get it wrong and rankings are cut in half and every backlink’s authority is wasted. Remember three core principles: use 301, not 302; map one URL to one URL instead of dumping everything on the homepage; and leave the redirects in place for 12 to 18 months before considering removal.
Three steps to roll it out. This week, crawl the whole site with Screaming Frog, export every 404 and 302 URL, and build an old-to-new mapping table. Next week, configure the 301 rules on the server and verify each one with curl and GSC. The third week, update your sitemap and internal links, then submit the new sitemap in GSC. After that, review every quarter.
One line worth remembering: a 301 is a relay baton for authority, not a permanent bridge. Hand it off correctly and the old page’s score carries over to the new page; fumble it and the score drops to the ground; and once the handoff is done, you still have to run the rest of the race yourself.