SEO: How to Create a 301 Redirect Map, for Site Redesigns

Editor’s Note: This is part two of a two-part series on creating a 301 redirect strategy as part of the website redesign process. Part one, “For Redesigns, Protect SEO with 301 Redirect Strategy,” we published previously.

In a website redesign where URLs change, whether your search-engine-optimization goal is to protect existing natural search performance or boost it to a new level, an ironclad 301 redirect strategy is critical. In “For Redesigns, Protect SEO with 301 Redirect Strategy,” my previous article, I outlined why 301 redirects are important to SEO, how to work the redirect strategy into the redesign timeline, and how to create a list of URLs to create a 301 redirect map.

Looking at the lists of current site URLs and redesigned site URLs — the old and the new — it’s time now to merge the two lists and create a spreadsheet that matches every old URL with the most relevant new URL possible. This is the 301-redirect map, the core of the redirect strategy.

Staring at a list of thousands of old URLs, some of which you had no idea existed, it feels like the task will never be completed. Excel’s filtering abilities make it more bearable, but you may also need to prioritize certain groups of URLs over others.

Prioritizing URLs to Redirect

Whenever possible, include all possible URLs in the 301 redirect map. If they’re indexed, or even just crawlable, they have some small amount of link authority. It may just be internal link authority, but it’s there. Knowing that the most link authority and trust I can hope to pass (via 301 redirects) to the new site is 85 percent of the old site’s authority, I want to wring every drop of authority from the old site. That means 301 redirecting every possible URL.

Sometimes the site is just too large or too haphazardly constructed to make a complete 301 redirect map possible. In that case, look to web analytics and Webmaster Tools to help prioritize the URLs on which to focus.

In web analytics, export the report for natural search visits by landing page. If a page has received even one visit from natural search, that means it’s indexed by at least one search engine and has at least a small amount of authority to preserve.

Naturally, pages that receive more natural search visits should be a higher priority to redirect than those that receive small amounts. Those that convert well and drive higher numbers of visits are the highest priority. Make sure to set the timeframe for the report long enough to account for any seasonality.

The “Links to My Site” report in Google Webmaster Tools offers another way to prioritize pages to include in the 301-redirect map. If a page has 50,000 links to it, it’s likely more authoritative than a page that has 500 or 5 links to it. This quick method only takes quantity of URLs into account, but keep in mind that link quality is more important in determining a page’s authority.

Completing the 301 Redirect Map

When the prioritization is complete, open the two lists of old and new URLs in Excel. Filtering for a common keyword found in the old URLs can also make quick work of matching a batch of old URLs to a new one. For example, if four URLs all contain “contact” in the URL, it’s possible that they can be all redirected to the new Contact Us page.

To filter in Excel, select the row that contains the headers for your data. The filtered row is highlighted in gray in the example below. Then select “Filter” from the “Data” menu in Excel. A box with an arrow in it will appear at the right of every cell in your highlighted row. Click on the arrow for the column you want to filter, select “Text Filters” and “Contains,” and then enter a word or phrase. In the example below we’re filtering the column “Current Site/OLD URL” for URLs containing the word “contact.”

This sample 301 redirect map filters URLs by common keywords.

In this very simple example of nine URLs, four URLs matched the criteria, and each was mapped to the new URL for the Contact Us page in the redesigned site.

Filtering can be used to find all of the URLs in a particular section of the site, or all of the URLs containing a specific product ID, or any number of ways. Sometimes an entire section will be deleted in a redesign and all of the URLs in that section can be redirected to a single new URL like the home page or a relevant category page.

Migrating to a New Platform?

If the redesign involves migrating to a new platform, the old URLs and the new may be in dramatically different formats. The old platform may use numeric identifiers in URLs, such as “http://www.oldsite.com/products/‎detail?id=2345”, and the new platform may use keyword URLs such as “http://www.newsite.com/prod-detail/next-best-product/”. Discuss URLs and 301 redirects with your developers. They may be able to recommend an easier way to redirect product and category pages based on identification numbers, even if the URLs displayed in the browser don’t show identification numbers.

When developers can’t find a more efficient solution, the crawl data used to create the list of old URLs can also help identify the content found on URLs that doesn’t contain keyword clues. For example, just looking at the URL “http://www.oldsite.com/products/‎detail?id=2345” you’d have no idea which product it housed. The crawl data from Link Sleuth or SEO Spider includes title tags for every URL crawled, however, so you can see that “http://www.oldsite.com/products/‎detail?id=2345” contains the Next Best Product, as in the example above. This enables you a way to match keywords from the title tag for the old URL to the new keyword URL. When matching on a large scale, try using Excel’s VLOOKUP formula to find matches quickly for you to scan for accuracy.

When the 301 redirect map is finished and every old URL is matched to a new URL, look for patterns to recommend basing the redirects on. Handing the developers a list of thousands of one-to-one redirects is guaranteed to meet with resistance. That many redirects would take a very long time to write and test, and would have a higher potential for error. Instead, try to identify patterns in the mapping that take care of more than one redirect at a time.

Handing the developers a list of thousands of one-to-one redirects is guaranteed to meet with resistance.

For example, maybe you can identify that the only URLs that contain the word “contact” will 301 redirect to the new Contact Us page. In that case, you could recommend that any URL on “http://www.oldsite.com/” containing “contact” 301 redirect to “http://www.newsite.com/about/contact-us/”. Be careful, however, because if any other URLs accidentally happen to match a pattern they will be redirected as well. For example, a product URL that contains the product name “contact adhesive” would match the word “contact” and would be erroneously redirected to the Contact Us page. Check carefully to be sure that the patterns you recommend will pertain only to the URLs you intend.

Redirect Testing and Measurement Plans

Testing the 301-redirect map is simple, really. Just crawl the redesigned site using Link Sleuth or SEO Spider — I address these and other handy SEO tools, in “My Favorite SEO Tools,” a previous article — to produce a report of the server header status returned for each URL and compare the output to the 301 redirect map. If each old URL is 301 redirecting to the intended new URL, the test is successful.
It’s important to crawl the site both in staging before launch and in production after launch, because there is so much potential for error with 301 redirects. Even the most experienced developer can miss a single character in one of a hundred redirects and accidentally redirect a batch of URLs to the wrong place. It’s also possible that the mapping or patterns were flawed before the redirects were written. Crawling to test the redirects is the only way to be certain that the redirects are passing both customers and link authority to the right pages.

How to Measure

The last piece of the redirect strategy is the measurement plan. The goal of the strategy is to preserve both natural search performance and link authority. Performance should be measured primarily by web analytics with rankings used as a secondary measure. Are the high priority pages receiving consistent or more visits from natural search after the redesign? If so, the redirect strategy was successful. If visits fell and remain consistently low, recheck the redirects as you’re looking for other culprits. If conversions fell, 301 redirects are not the issue. The redirect preserves authority, which preserves ranking ability, which drives visits to a site. What customers do once they get there is beyond the influence of a redirect.

It’s harder to measure link authority, but it can be approximated with Google Webmaster Tools’ “Links to My Site” report. The number of links attributed to the old URLs should gradually decrease and a similar number of links should be attributed to the new URLs should. The transition is extremely fuzzy, however, and can take months to update. Rest assured that if natural-search-referred visits are strong, the authority is has passed as intended regardless of what the “Links to My Site” report says.

In a redesign when developers have too many things to worry about as it is, the redirect strategy sometimes encounters resistance. To pave the way, make sure everyone on the team understands from the beginning what the redirect strategy is, why it’s critical to SEO performance, and when it needs to be worked into the redesign timeline.