Decide when each classic site becomes modern, or why it stays classic

Chapters 23 to 26 chose where each site goes, and Chapter 27 what is archived first. Many of those sites are classic, with publishing features, master pages or script on their pages. Microsoft has dated how much of that SharePoint Online keeps. From 1 March 2027 no tenant can create a classic publishing site or activate the publishing feature; from 1 October 2028 classic user-created pages in every tenant are read-only, and the setting that blocks custom script is enforced for good; tenants created from 1 March 2027 start that way (upcoming changes, checked on 7 November 2026). Modernising has a calendar, and a migration is one of the moments it can happen.

For each classic site, is it modernised before it moves, while it moves, after it lands, or left classic, and what decides which?

The decision this chapter leads to is a modernisation disposition for every classic site collection (before, during, after, or stay classic), recorded with its reason and its owner before its wave.

Which sites this chapter is for

Every site collection on a SharePoint Server 2016 or 2019 farm with classic templates, pages, publishing features or customisations, attached to Subscription Edition (Chapter 23) or copied into SharePoint Online (Chapter 24). Chapter 15's readings name what each one uses, and Chapter 26's dispositions come first: a site that will not migrate needs no modernising.

What modern means where the site lands

In SharePoint Online, Microsoft's modern sites are group-connected team sites and communication sites (modernise classic sites); each is a site collection that can join a hub, which replaces a subsite tree's inherited navigation (modern experience guide, both checked on 7 November 2026).

On SharePoint Server, 2016 is classic, and 2019 added modern sites, pages, web parts, lists, libraries and search (differences between 2016 and 2019, checked on 7 November 2026). On 2019 and Subscription Edition alike you choose between modern team and communication sites and the classic experience, and "Hub sites aren't available in SharePoint Server" (sites and site collections, checked on 7 November 2026). At release, Subscription Edition added list and library web parts that edit in place, modern document sets and a modern search results page (new in Subscription Edition), and its feature updates added more, several first in the Early release ring: bulk editing, Excel-style column formatting and a Button web part in 22H2; SPFx v1.5.1, column totals and wider use of the modern sharing dialog in 23H1; SPFx component upgrades and Suite Bar branding in 23H2; the Modern People Card and a new editor in the Text and Events web parts in 25H2 (all checked on 7 November 2026). None of the feature update pages, 22H2 to 26H2, lists hubs, groups or page conversion.

Microsoft's routes, and whose they are

Sources for the table: create a migration task, connect to a Microsoft 365 group, Set-SPOSiteOffice365Group, communication site experience, page transformation, in place or cross-site, publishing portals, branding, customisations, SPMT FAQ and workflow migration, all checked on 7 November 2026.

The modernisation tooling and "all other PnP components" are open source and community-supported, with no Microsoft SLA (modernise classic sites, above). Page transformation "only supports SharePoint Online as the target platform for modern pages" (in place or cross-site, above), so we know of no route that converts a page on a farm: there, a modern page is built by hand. We would run any community route on a copy first: "Opening without an error isn't sufficient validation" (page transformation, above).

What the migration tool changes, and what it leaves

SPMT modernises two things during the copy. For a site migrated with its subsites, "Switch to the modern site structure" promotes "all level-one subsites to site collections" and can register the destination as their hub or join them to an existing one (release notes; create a migration task, above), as Microsoft's team sites migration guide recommends (both checked on 7 November 2026). Chapter 12 decides which subsites become sites, and a site it flattens only in part does not fit that option; where deeper subsites land, the pages do not say and we do not know, so test on a copy.

The rest arrives classic, or not at all. SPMT's scan flags any page other than a wiki or web part page (scan codes, checked on 7 November 2026); it migrates neither master pages nor custom list forms (the forms are Chapter 20's), and "SPMT decides the destination site template" (SPMT FAQ, above). Script web parts migrate only while custom script is allowed on the target, and SPMT's pages disagree on how long: its settings page allows it within 24 hours of the run and says it "switches back to Blocked within 24 hours", while its supported web parts page asks for it from 24 hours before until the migration completes. Its "Temporarily allow migration of scripts" setting "automatically allows the migration of scripted web parts" (SPMT settings, both checked on 7 November 2026), and once the dates above make the block permanent, SPMT's pages imply they no longer migrate. No SPMT page we read describes connecting a site to a group or making a page modern.

What has no modern equivalent

These need a decision, not a conversion:

• Wiki pages. "There is no modern equivalent of a Wiki page" (differences between 2016 and 2019, above); online, Text and Markdown web parts cover "many of the same scenarios" (publishing sites to communication sites, checked on 7 November 2026).
• Classic web parts. Many, the Script Editor among them, have "no out-of-the-box modern equivalent" (customisations, above); Highlighted content does Content Query's job without custom display templates, and Summary Links has no one-to-one successor (publishing sites to communication sites, above).
• Menus and edit panes. Modern pages take no custom entries in the site actions menu, and modern lists cannot yet reproduce JSLink in the edit pane (customisations, above).
• Publishing as a model. Communication sites support none of the classic publishing feature, the classic Record Center, Save site as template or subsites, and variations become multilingual pages, a folder per language in one site (same source; modern experience guide, above).

The owner chooses: rebuild the need another way, accept the loss in writing, or keep the site classic where classic still runs, recorded as Chapter 15 records customisations.

Staying classic on Subscription Edition

Subscription Edition's deprecated and removed list names no classic site, page or publishing feature (deprecated or removed, checked on 7 November 2026), and Microsoft still adds to them: variations cmdlets in 23H1, web part drag and drop on publishing pages in 25H2's Early release (both above). Staying classic there is supported, and what it defers is paid on the way out:

• The remedy needs a retired tool. SPMT refuses a customised page and says to restore its template with SharePoint Designer (SPMT troubleshooting), whose 2013 version left support on 14 July 2026 (ending support in 2026, both checked on 7 November 2026).
• The routes stop at 2019. SPMT reads SharePoint Server 2010 to 2019 (SPMT overview, checked on 7 November 2026), and page transformation's sources end at 2019 (in place or cross-site, above). Neither names Subscription Edition; whether either reads it, we do not know.
• The landing has moved. From 1 March 2027 a classic publishing site has nowhere classic to land, and classic pages copied online are read-only once their phase applies, with script-based elements at risk (upcoming changes, above).

We would keep a site classic on Subscription Edition when its life there is the plan, and record beside it what a later move online would rebuild.

Before, during, after or stay classic

• Before, on the old farm, takes things away: unused pages, customisations Chapter 15 eliminates, custom master pages reverted, customised pages restored. 2016 and 2019 have been out of support since 14 July 2026 (ending support in 2026, above), so we would build nothing new there; whether a modern page built on a 2019 farm reaches SharePoint Online as one, we do not know.
• During exists only for a copy: SPMT's structure and workflows, and pages transformed cross-site, each validated by its owner. An attach upgrades the database as it is.
• After: online, group connection, the communication site experience and in-place transformation; on Subscription Edition, modern pages by hand, column formatting and SPFx within the versions Chapter 16 lists.
• Stay classic: on Subscription Edition, while the site lives there; online, only for pages their owner accepts as read-only. List and library views and list forms are outside that change (upcoming changes, above).

What decides, site by site: the destination, which sets the routes; the template, since a publishing portal goes to a new communication site and cannot be group-connected (modernise classic sites, above); the elements with no equivalent; an owner to validate; and use, since Microsoft recommends transforming "only the pages that are frequently used" (same source). Purview audit events show that use online (upcoming changes, above), Chapter 14 on the farm.

A disposition is a date and a reason. "Later" is neither. We recommend recording each site's disposition, the elements it settles, the route and whose it is, and its validating owner, before Chapter 33 fixes its wave.

Out of scope

Designing hubs, the home site and navigation is a decision of its own, as Chapter 12 says. Archiving first is Chapter 27, tooling Chapter 29, waves Chapter 33 and validation Chapter 34. Group naming, Teams, adoption, training and licensing are not covered.

Before you continue

• Every classic site collection in scope is listed with its destination, template and classic elements
• Every element with no modern equivalent has its owner's decision: rebuilt another way, lost in writing, or kept classic
• Every copy into SharePoint Online has its site structure option and hub association chosen from Chapter 12's dispositions
• Every page route names whose tool it is and the owner who validates each page
• No publishing site counts on a classic destination online after 1 March 2027, and every classic page kept online has an owner who accepted it read-only
• Every site kept classic on Subscription Edition records what a later move online would rebuild
• Every site has one disposition (before, during, after or stay classic) and its reason, recorded before its wave

Download chapter 28 (PDF)Same text, same tables, same sources as this page.