The short answer
If you want to keep a sideblog but stop running it from an old main identity, the realistic goal is to hand over management of that blog, not to fuse two accounts into one. Those are different operations, and Tumblr’s documentation only supports the first.
Tumblr does not combine two existing accounts or swap primary and secondary blog types. Source
That single sentence rules out the fantasy version of this task — one tidy “merge” button that folds your sideblog into another account, keeps everything, and retires the old login. Plan around access transfer instead, and treat URL reuse and content migration as separate questions with their own answers.
What the documented workaround actually does
Its documented sideblog-management workaround is to invite another account into the existing sideblog as a group-blog member and make it an admin. Source
The mechanics worth noticing:
- The blog stays where it is. You are adding a member to the existing sideblog, not creating a new home for it.
- The incoming account needs to be a member and then an admin, so the handover is two steps, not one.
- Because the blog itself is unchanged, its posts, theme and audience relationship stay attached to that blog rather than to either account.
What this does not do is equally important: it does not give the new account ownership of your primary blog, and it does not turn the sideblog into a primary blog. If your goal was “make this sideblog my main blog on the new account,” the workaround does not deliver that.
Management access is not URL reuse
A common assumption is that if the new account creates a fresh primary blog and claims the old sideblog’s address, the old blog has effectively moved. The documentation does not support that reading.
Creating a new primary blog and taking a secondary blog’s URL does not automatically transfer content, settings, followers or likes. Source
So the address and the blog are two different things to reason about. A URL that becomes available and gets picked up by a new blog is a new blog wearing an old name — not the old blog in a new place. Anything you cared about on the original sideblog (its posts, its settings, its followers, its likes) does not come along for that ride.
This is why “merger” language is misleading here. A merger implies continuity of the thing itself. What you can actually get is either continued management of the same blog by a different account, or a separate new blog that happens to reuse an address — and those are not interchangeable.
Decide which outcome you actually want
| Your goal | Supported path | What you should not assume |
|---|---|---|
| Keep the sideblog running, run it from a different account | Invite the other account to the sideblog as a group-blog member and make it an admin | That the sideblog becomes a primary blog, or that the two accounts become one |
| Keep the sideblog’s address on a brand-new blog | Create a new primary blog and take the address if it is available | That content, settings, followers or likes carry over |
| Combine two existing accounts into one | No documented path | That any workaround produces a true merger |
| Retire the old account entirely | Hand over management first, then deal with the old identity separately | That removing a login connection or editing a profile deletes stored data |
Read the table as a scope check, not a menu. If your goal lands in row three, the honest answer is that the documented material does not describe a way to do it, and you should choose between rows one and two instead.
A handover checklist
Work in this order. The sequencing matters more than the individual steps, because the failure mode is losing control of a blog you meant to keep.
- Write down what the sideblog currently is. Its address, its role in your setup, and anything you would be upset to lose. This becomes your comparison baseline later.
- Decide which account should end up managing it. A person or an account you control — not a placeholder you cannot get back into.
- Add that account to the sideblog as a group-blog member. This is the documented entry point; expect it to be a membership step before it is an admin step.
- Make it an admin. Membership alone is not the same as administrative control.
- Confirm from the new account that it can actually manage the right blog. Log in as the new account and check that you are looking at the intended sideblog, with the intended permissions. Do this before you touch the old account at all.
- Only then deal with the old identity. Whether you keep it dormant or wind it down, that is a separate task with its own risks.
Step five is the one people skip. “I sent the invite” is not evidence that the new account can administer the correct blog. Verify from the receiving side, while the old account still exists as a fallback.
Failure paths to expect
- You invited the wrong account. Handled early, this is trivial: remove the membership before promoting anything. Handled after you have wound down the old account, it is not.
- You promoted a member but never checked admin rights. A member who cannot administer the blog is not a handover. Test the permission, not the invitation.
- You assumed the sideblog would become primary. It will not. If your plan depended on that, the plan needs rewriting before you start.
- You grabbed the old address with a new blog and expected continuity. Per the documentation, content, settings, followers and likes do not follow the URL. If those mattered, you have created a lookalike, not a successor.
- You removed your own access too early. Keep a recovery path you control until the new admin has been confirmed working. Removing a login connection is not the same as deleting an account, and an edited or empty profile does not establish that stored data is gone.
Where this fits with cleaning up the old identity
Handing over the sideblog is one half of the job; the old main identity is the other half, and it deserves its own pass rather than being rushed in the same sitting. Once the new admin is confirmed, the natural next task is deciding what should remain findable about the old account and what should not. Our guide to stopping old accounts from being found during footprint cleanup covers that work in its own right.
Keep the two tasks mentally separate. A sideblog that is now managed by someone else is still the same sideblog, and an old account you have stopped using is still an account with a footprint until you address it deliberately.
If you want to check what is publicly visible
Before and after a handover, it can help to see what a stranger would find under the relevant usernames. TraceSeek, the app covered by TruthsSeek, checks usernames against 3,000+ platforms, and the first scan is free without registration or login; the product describes a scan as taking 20–30 seconds. Those are product statements rather than independent measurements.
Treat any results as leads. A matching username, photo or bio on another platform is a hint to look closer, not proof that the same person or account is behind it, and a username search is not a complete inventory of anyone’s accounts. For this particular task, the value is narrower: confirming that a sideblog’s public presence looks the way you expect after management changes hands.
If the sideblog’s address or display name changes as part of the handover, expect the old and new versions to coexist in search results and in other people’s links for a while. That is a visibility question, not a management one, and it is worth checking rather than assuming.