Writing a Redirect Map That Holds Up After Launch

Every URL that changes during a migration needs an answer to one question: where should someone who arrives here end up? A redirect map is the written answer for every old address. It is simple in concept and easy to get wrong in detail, so it pays to approach it methodically.

Use permanent redirects for permanent moves

When a page has moved for good, a permanent redirect, usually a 301 or 308 status, tells browsers and search engines that the new address replaces the old one. Temporary redirects suit genuinely temporary situations such as maintenance pages. Using the right type communicates intent clearly.

Map one to one wherever possible

Each old URL should point to the single most relevant new page. A retired service should redirect to the closest current service or a page explaining the change, not to the home page. One-to-one mapping is more work, but it is what helps visitors and preserves relevance.

Combine individual rules with patterns

Large sites often have families of URLs that change in the same way, for example a blog moving from a date-based path to a simpler slug path. Pattern rules handle these efficiently. Write pattern rules carefully and test them against real examples, because a loose pattern can capture URLs it was never meant to touch. Individual rules for important pages should take precedence over patterns.

Avoid chains and loops

If an old URL already redirects to another old URL, and that URL now redirects to a new page, visitors pass through a chain. Update the original rule so it points directly to the final destination. Check for loops, where two rules point at each other, which leave visitors stuck.

Handle variants consistently

Decide on canonical forms for protocol, host and trailing slashes, then redirect other variants to them. Make sure query strings are handled intentionally: pass through campaign parameters if analytics needs them, and drop parameters that only existed in the old system.

Include files and media

PDFs, images and downloadable resources often have their own inbound links. Include them in the map when their paths change. Pay particular attention to files linked from printed material or partner websites.

Test before launch

On a staging environment configured with the redirect rules, run the full list of old URLs through an automated check that records:

1. The status code returned.
2. The final destination after following redirects.
3. The number of hops.
4. Whether the destination returns a successful status.

Fix anything that returns an error, lands on an unexpected page or takes more than one hop.

Monitor after launch

After launch, watch server logs or monitoring for requests that return not-found errors. Search console reports and analytics can reveal old URLs you did not know about. Add rules for any with genuine value. Keep redirects in place for the long term; removing them early can break old links that still circulate.

Keep the map as documentation

Store the redirect map with the project so future changes can build on it. When someone renames a page next year, they should add to the map rather than start from scratch. Redirects accumulate value over time when they are maintained deliberately.