Merging two websites into one is a migration with an extra problem: you are not just moving URLs, you are deciding which of two versions of overlapping content survives. That decision, made badly, is what causes most merge failures.
The mechanical process is on SEO migration. This page covers what is specific to combining sites.
Decide what you are keeping before you touch anything
Merges usually involve two sites with overlapping coverage: two service pages about the same service, two about-us pages, two blogs covering the same topics. Every overlap needs a decision.
- Which page survives for each overlapping topic. Usually the one with more traffic, better rankings or stronger links, not the better-designed one.
- What gets merged rather than discarded. The losing page often contains sections worth keeping.
- What gets dropped entirely, which is legitimate for genuinely redundant content.
- What moves unchanged, where only one site covered it.
Doing this after the merge, when both versions are live on one domain, means you have created cannibalisation and then have to unpick it. Decide first.
Which domain survives
- Compare authority, backlink profiles and organic performance rather than brand preference.
- Where one domain is substantially stronger, that is usually the answer regardless of naming.
- Where the weaker domain is the preferred brand, accept that you are taking a real hit and plan for a longer recovery.
- A brand-driven choice is legitimate. It just should be made knowingly rather than by default.
The redirect map is bigger than it looks
- Every URL from the retiring site needs a decision, not just its main pages.
- Overlapping topics redirect to the surviving version, which means many-to-one mapping.
- Do not redirect everything to the homepage. See soft 404.
- Content with no equivalent either moves across or returns 410.
- Reconcile against Search Console indexed URLs for both properties, not just crawls.
Watch for after launch
- Cannibalisation where both versions were published rather than merged. This is the commonest failure.
- Internal links still pointing at the retired domain.
- Duplicate content where near-identical pages both survived under different URLs.
- Old domain left live rather than redirecting, so both versions remain indexed. See old URLs still indexed.
- Search Console handling for the retiring domain. See Search Console domain migration.
Realistic expectations
A merge is a bigger disruption than a standard migration. The combined site should eventually be stronger than either alone, since authority consolidates rather than splits, but the settling period is longer and a temporary dip is normal on both sets of URLs.
Frequently asked questions
Will merging make us stronger?
Usually, over time. Two sites competing for the same terms are weaker than one consolidated site. The gain arrives after the settling period, not immediately.
Which domain should we keep?
The stronger one, unless brand considerations override that. If you keep the weaker domain, expect a longer recovery and plan for it rather than being surprised.
Can we keep both sites running?
You can, but they will compete for the same queries and split your authority. If they serve genuinely different audiences that may be acceptable; if they overlap, merging is usually better.
How long until it settles?
Longer than a standard migration. Several months for a site of any size, because both URL sets have to be reprocessed and the consolidation reassessed.
Consulting CTA
If you are combining two sites, book an SEO consultation before deciding which pages survive, since that decision drives the whole redirect map.