Internal links to redirected URLs: updating links that take a detour

What it looks like

Before

<a href="http://example.com/2019/mug-guide">our mug guide</a>

After

<a href="https://example.com/guides/mugs/">our mug guide</a>

How WordPress sites collect them

• Slug changes. When you edit a post's slug, WordPress remembers the old one and redirects it, so nothing visibly breaks. (It does not do this for pages and other hierarchical types.) Links typed into other posts keep the old address indefinitely. Hydrogen SEO's Auto Redirection covers posts, pages and terms by adding a visible 301 rule.
• Protocol and host changes. A site moved to HTTPS, or from www to the bare domain, with years of content containing absolute links in the old form.
• Missing trailing slashes. Hand-typed links such as /about on a site whose permalinks end in a slash. WordPress redirects each one.
• Permalink structure changes, such as removing dates or the category base from URLs.
• Menu items saved as Custom Links. A menu item created by choosing a page updates when the page's URL changes. One created by pasting a URL does not.
• Hard-coded links in templates, widgets and footers.

Find them

Check one page. This prints every internal link on a page whose target does not return 200:

page=https://example.com/blog/some-post/
curl -s "$page" | grep -oE 'href="https?://example\.com[^"#]*"' | cut -d'"' -f2 | sort -u | while read u; do
  code=$(curl -s -o /dev/null -w "%{http_code}" "$u"); [ "$code" != "200" ] && echo "$code $u"
done

Run it on the homepage first. Anything it finds there in the header or footer is site-wide.

Check from your redirect list. Every source in your redirect rules is a URL that may still be linked. In Hydrogen SEO, the list is under Hydrogen SEO → Redirections. For each source path, search your content:

wp db query "SELECT ID, post_title FROM wp_posts WHERE post_status='publish' AND post_content LIKE '%/2019/mug-guide%'"

Check the whole site. A crawler that reports internal links by status code will list every 3xx target with the pages linking to it. Hydrogen SEO's site audit covers the neighbouring problem, internal links that are broken outright, across the whole site.

Fix them

1. Navigation and templates first. Edit menu items under Appearance → Menus or the Site Editor's navigation block, and replace Custom Link entries with the page itself where possible. Then footers, sidebars and reusable blocks.
2. Single links in content. Edit the post and repoint the link at the final URL.
3. Patterned changes in bulk. For a protocol, host or structural change that affects many posts, use WP-CLI after a database backup:

wp search-replace 'http://example.com/' 'https://example.com/' wp_posts wp_postmeta --dry-run
wp search-replace '/2019/mug-guide' '/guides/mugs/' wp_posts --dry-run

Review the count, then run without --dry-run. Be specific with the search string so that you do not rewrite URLs that merely start the same way. 4. Check where the redirect leads. If the final destination is not a good match for the link's anchor text, as when an old article was redirected to a category page, choose a better target for that link instead of the redirect's.

Keep the redirects after updating the links. External sites, bookmarks and Google's index still use the old addresses.

Links to chains and to redirects that go nowhere useful

While you are in the list, note two worse cases. A link whose target redirects more than once is a redirect chain; fix both the link and the first rule so it goes straight to the end. A link whose redirect ends on the homepage, because of a blanket rule for deleted content, is effectively a broken link: Google often treats irrelevant redirects to the homepage as soft 404s. Repoint it or remove it. Our guide to fixing redirect chains covers the rule side.

Prevent new ones

• Link to pages using the editor's link search, which inserts the current permalink, instead of pasting URLs from an old document.
• After changing a slug, search for the old slug and update the links that week, while you remember why it changed.
• When importing content, run a search-replace for the old domain before publishing.
• Before deploying a batch of redirects, run the old and new URL pairs through the redirect rule generator, which warns about chains within the list.

Confirm the links now resolve directly

Run the one-page check again on the homepage and on two or three heavily linked posts; it should print nothing. Hydrogen SEO's internal link counter will show the link counts for the final URLs rising, since links that previously named the old address now name the page itself. The free SEO audit counts the internal links on a page and reports links that fail outright; redirected links are not flagged there, so use the loop above.