Build a 301 redirect map from a crawl
By Ismael · Reviewed
A 301 redirect map is a table of old URLs, their new destinations and the status that sends both users and crawlers to the right page. SiteBienfait generates one from a crawl before a migration. Google Search Central, updated 2026-04-14, classifies 301 and 308 as permanent redirects that Google treats as a signal that the redirect target should be canonical.
What is a 301 redirect map?
It is a CSV or spreadsheet with three columns that matter: the old URL as requested, the new URL that should answer, and the redirect decision. A fourth column records why. Without that reason, a reviewer cannot tell a deliberate merge from a mistake, and the map cannot be maintained after launch.
The map is not the server configuration. It is the reviewed source that generates the configuration, which is what makes it possible to test, count and roll back.
How is a redirect map built from a crawl?
Begin with the live URL inventory. Crawl the site from the homepage with internal links enabled, then merge in the XML sitemap, Search Console’s indexed pages and analytics entries for anything not linked. Normalise the rows: lowercase the host, settle trailing-slash behaviour, decide how query strings are treated, and strip tracking parameters.
Next, list the new site’s routes from its built output rather than its design file, because the built output is what a crawler will see. Match old to new by path first, then by title, then by primary heading and 301 target page.
Google Search Central, updated 2026-08-20, describes this as preparing a URL mapping before redirects are configured, and warns against wildcard shortcuts that leave no per-URL record. The exception is a straight domain change, where a host-level rule is legitimate; a redesigned information architecture is not that case.
Which redirect should each row use?
Permanent, server-side 301 or 308 for every URL that moves for good. Google Search Central, updated 2026-04-14, notes that server-side redirects have the highest chance of being interpreted correctly, with meta refresh behind them and JavaScript redirects reserved for cases where nothing else is possible.
A 302 belongs only on pages that will return, such as a maintenance page. The same page explains that temporary redirects leave the source URL as the canonical one.
Removed content should not receive a redirect at all. It returns 404 or 410, per Google Search Central, updated 2026-08-20. That decision belongs in the map as a row, not as an omission, because a crawl that finds a 404 is evidence that the removal was intentional.
How long should the redirects stay live?
At least one year, and longer where links keep arriving. Google Search Central, updated 2026-08-20, recommends keeping redirects for as long as possible, generally at least one year, to give Google enough time to recrawl and to let external links be reassigned.
From the visitor’s side, the same page suggests considering redirects indefinitely, while updating high-volume external links to the new URLs so fewer requests take the slow path.
How is the map tested?
Test in two passes. Before cutover, request each old URL against the new host and confirm the status code and destination. After cutover, crawl the old URL list and record four values per row: status, redirect target, final status, and the canonical of the final page. Google Search Central, updated 2026-07-10, is clear that the canonical tag on the new page should name the new URL, not the one that redirected.
Then compare counts: rows in the map, rows returning 301, rows returning 404, and rows with no match. Any mismatch is either a missing route or a map error, and both are cheaper to fix in the preview than after the old site is gone.
SiteBienfait’s migration route consumes the map as part of a change set and blocks a release when a mapped URL regresses. The redirect map checker does the first pass in the browser: paste the live URL list and the new URL list, and it reports which paths are preserved, which need a redirect and which are missing. The website migration SEO checklist places the map in the wider cutover sequence.
Sources
- Google Search Central, Redirects and Google Search, last updated 2026-04-14.
- Google Search Central, Move a site with URL changes, last updated 2026-08-20.
- Google Search Central, How to specify a canonical URL, last updated 2026-07-10.
Questions
01 What is a 301 redirect map?
A table with one row per old URL, the new destination that replaces it and the status code that carries the move. It is both the implementation list for the server and the review document for the site owner.
02 Should every old URL redirect to the homepage?
No. Google Search Central, updated 2026-08-20, says removed or merged content should return a 404 or 410 on the new site rather than redirect to an unrelated page. A blanket homepage redirect makes deliberate removals impossible to audit.
03 How long does a redirect map stay in place?
Google Search Central, updated 2026-08-20, recommends keeping redirects for as long as possible, generally at least one year, because that is how long the recrawl and link reassignment can take.
04 How is a redirect map tested before launch?
Request every old URL from the new host without following redirects, confirm a single permanent redirect, then follow it to a 200 response whose canonical points at the new URL. A crawl after cutover repeats the same check at scale.