Decide what the structure becomes before the tooling is chosen

Information architecture is the part of the estate that arranges content rather than holding it: the addresses sites live at, how deep they nest, the content types and term sets that describe documents, the navigation between them, and the shape of the lists and folders underneath. Chapter 2 counted site collections, databases and items. This chapter reads how they are arranged, because the two destinations treat that arrangement in opposite ways.

Does the structure you have survive the destination, or does the destination force a redesign, and where?

The decision this chapter leads to is a disposition for each part of the structure (keep, flatten or redesign), recorded with the measurement behind it, before any migration tool is chosen.

Which estates this chapter is for

A SharePoint Server 2016 or 2019 farm whose content goes to Subscription Edition by database attach (Chapter 23) or into SharePoint Online by copy (Chapters 8 and 9). An attach upgrades "only the content for your environment and not the configuration settings", and attaches "the site collections inside that database" (upgrade content databases, checked on 6 November 2026). A copy recreates what the tool is told to, at addresses the service decides. Who may open what is Chapter 13's question.

What each destination does with each part

Sources for the table: upgrade content databases (above), host-named site collections, change a site address, SharePoint limits, planning hub sites, Copy-SPTaxonomyGroups and the list view threshold, all checked on 6 November 2026; the Managed Metadata rows on Subscription Edition follow Chapter 10.

The Subscription Edition column is short because an attach changes almost nothing, and that is the risk as much as the attraction: whatever does not work today arrives working the same way. The SharePoint Online column is the design work.

Addresses, subsites and navigation

On Subscription Edition you recreate each web application with "the same URL (including name, port, and host header)" and its managed paths (upgrade content databases). An attach cannot convert a host-named site collection into a path-based one; Microsoft does that with Set-SPSite on a running farm (host-named site collections). In SharePoint Online none of that layer survives: even with a custom domain, "all your SharePoint and OneDrive URLs use the original onmicrosoft.com domain" (change your SharePoint domain name, checked on 6 November 2026), and a site sits under /sites or /teams. Every old address needs a new one, and that map is the link inventory Chapter 9 spends at cutover.

Microsoft's server guidance recommends a site collection per unit of work instead of subsites, because such site collections "make it easier when migrating your SharePoint Server farm to SharePoint in Microsoft 365"; it also says hub sites "aren't available in SharePoint Server" (sites and site collections, checked on 6 November 2026). On Subscription Edition, flattening is a choice made for a later move, with nothing to join the results. In SharePoint Online subsites remain "a classic feature", but Microsoft recommends sites joined by hubs (planning hub sites, SharePoint limits). Flattening has a price: subsites are "a physical construct reflected in the URL for content", a site joins one hub only, and hub navigation stops at three levels (planning hub sites), so a deeper tree has no one-to-one copy.

Two limits can decide for you. SharePoint Online allows 2,000 subsites and 2,000 lists and libraries per site collection, while the server's list threshold is 2,000 per site (SharePoint Server limits, checked on 6 November 2026). A site collection above either number, counting the lists of all its subsites, cannot arrive as one site.

Navigation follows the hierarchy. Managed navigation builds a publishing site's menus from a term set rather than from the site's structure (managed navigation, checked on 6 November 2026), and both kinds arrive on Subscription Edition unchanged. In SharePoint Online the "inherited" navigation of a subsite tree is not available in the modern experience, and hubs take its place (modern experience, checked on 6 November 2026). Record each site's provider and every link holding an absolute address, because the address map breaks them.

Content types and term sets travel apart from the content

On the server, the site collection named as content type hub of a Managed Metadata service application shares its content types, and each service application keeps "its own database containing the term set, terms, keywords" (plan for managed metadata, checked on 6 November 2026). Any site, subsites included, can also define "unique content types and site columns" (sites and site collections). Measure per site the content types received from the hub, those defined there, and names defined twice with different columns. On Subscription Edition all of it stays, and Chapter 10 records the hub's address to set it again.

In SharePoint Online the hub's address is fixed: content types copied from a farm land in /sites/contentTypeHub, whose "site URL is hard coded and can't be changed" (hybrid taxonomy and content types, checked on 6 November 2026), and publishing from the content type gallery makes a content type available to every site (publish a content type, checked on 6 November 2026). Decide which content types become the tenant's published set and which stay local to one site.

The term store is decided before anything that uses it moves, because each managed metadata value records its term's ID (TermGuid, checked on 6 November 2026). The route Microsoft documents, Copy-SPTaxonomyGroups, copies term groups "while maintaining the IDs of the terms, term sets, and term groups" (plan hybrid taxonomy, checked on 6 November 2026), with three edges: "Once a Taxonomy Group is copied, it cannot be re-copied" (Copy-SPTaxonomyGroups); Active Directory groups assigned in term sets are lost (hybrid taxonomy and content types); and local, site-specific term sets "can't be replicated" (plan hybrid taxonomy). Every farm feeding the tenant also shares one set of limits: 1,000 global term sets, 1,000 global groups, one million terms (SharePoint limits). So the cleaning happens once, before the copy. We do not know of a documented route that brings a local term set across with its IDs: decide each one (local in its new site, merged into a global term set, or retired) and test how its values arrive.

Lists, folders and paths that fail on arrival

Both platforms start from a list view threshold of 5,000 items per operation. On the server an administrator can raise it or open a daily time window; in SharePoint in Microsoft 365 it "can't be changed" (the list view threshold). A view that works only because the farm allows more fails in SharePoint Online, and works on Subscription Edition only if the new farm is set the same way, since an attach brings content, not configuration. Both hold 30 million items in a list, so the remedy is indexed columns and filtered views, not smaller lists. Above 100,000 items, permissions change too: Chapter 13.

For folders, Microsoft's guidance for SharePoint Online is that structures "with more than one or two levels of nesting create a significant discoverability burden for users" (introduction to information architecture, checked on 6 November 2026). Record the deepest folder in every library.

SharePoint Online allows 400 characters for "the entire decoded file path, including the file name" (SharePoint limits). SharePoint Server 2019 raised its limit from 260 to 400, counting "everything after the server name and port number in the URL" (new in 2019, checked on 6 November 2026), yet a path that fits there can still fail on arrival: Microsoft warns, for moves between tenants, that the source path "is combined with the new user or site name on the Target" (cross-tenant migration, checked on 6 November 2026). Flattening a subsite or renaming a library changes that prefix, so we would measure every path with its destination address in front.

Microsoft lists " * : < > ? / \ |, leading and trailing spaces, and names such as CON, desktop.ini, _vti_ anywhere or forms at a library's root as invalid (restrictions and limitations, checked on 6 November 2026), and its own migration tool either replaces each invalid character with one you choose or skips the file (SPMT settings, checked on 6 November 2026). Size rarely bites: no 2016 or 2019 file exceeds 15 GB (SharePoint Server limits) and SharePoint Online takes 250 GB, though a list item attachment stops at 250 MB (SharePoint limits), so count the attachments above it.

Keep, flatten or redesign, before the tool

For Subscription Edition, keep is the default for every row; what you set again by hand is the address layer, the hub's address and the throttling. Keep also carries every problem unchanged: deep subsite trees, lists that work only under a raised threshold, local term sets nobody owns.

For SharePoint Online, that column of the table is a design brief. A structure nobody decided is decided by the tool, one renamed file, skipped file or once-only taxonomy copy at a time. We recommend writing each disposition, with its measurement and its owner, before tooling is evaluated in Chapter 29, because what the tool has to do follows from it.

Out of scope

Permissions and sharing are Chapter 13; what search indexes is Chapter 11. The rules the destination's sites must meet are Chapter 6, and designing its hubs, home site and menus is a decision of its own, not covered here. Custom pages, master pages and other customisations are Chapter 15, and modernising classic sites first is Chapter 28. Sites that should not move at all are Chapter 26.

Before you continue

• Every web application, managed path and host-named site collection is listed with the address it will have at the destination
• Every site collection has its subsites, deepest level and lists counted, and each subsite is marked keep or flatten
• Each site's navigation provider and every link with an absolute address are recorded
• Every content type used by more than one site is marked tenant or local, and duplicate names are resolved
• Every term group and local term set has a decision, and the groups to copy are final before the single copy
• Lists above 5,000 items, folders deeper than two levels and the old farm's throttling settings each have a disposition
• Every path is measured with its destination address in front, and invalid names are counted, before a tool is chosen

Download chapter 12 (PDF)Same text, same tables, same sources as this page.