See which working links broke after a migration
A migration creates two kinds of 404: ones that already existed, and ones you just caused. Mortise is built to separate those, if you time the baseline.
No card required. 1 site and 200 pages on the free plan.
Run the baseline on the site you mean to protect
Add the host, verify it, and finish a crawl while the important links still work. That crawl is silent. Links that already 404 are known. Links that return a working status are the ones that can alert later.
If you add Mortise only after the launch, the first crawl baselines the new site, including launch-day 404s. Those known failures will not alert. You can still read them on the broken list after a second crawl. They are just not “new” to Mortise.
What a useful alert looks like after launch
A post still links to a campaign path that was ok before cutover. The path now returns 404 or 410 on two crawls. New breaks shows the URL and the source page. You fix the source. Mortise does not write redirects for you.
Give the site two crawls after the change before you treat the result as confirmed. One 404 is held as waiting for a second crawl.
What this will not catch
Mortise does not compare two hostnames, audit redirect maps, or score SEO. If the public HTML does not link to a URL, that URL is not in the crawl. Pages blocked by robots.txt are skipped. A content or design change that keeps the same URLs working is invisible here. For page-content changes, a different Litework tool is a better fit.
Questions
Should I delete the site and re-add it after launch?
Only if you want a new baseline of the launched site. Doing that forgets the pre-launch working set, so launch 404s will not alert.
How soon after launch should I crawl?
When the public site is reachable and verification still passes. Confirmation takes a second crawl, so a Pro daily schedule or a later manual run is part of the check.
Does Mortise test the old domain and the new domain?
Each host is its own site, with its own verification. It does not automatically pair a redirect from an old domain.