Six weeks before the acquisition close, Marcus gets a message from the CISO: migrate everything in SharePoint to the parent company's Microsoft 365 tenant. He has eight years of accumulated content across 14 site collections, minimal governance, and no inventory of what is actually there. The migration window is tight. His first move is not to the migration tool - it is to understand what he is actually working with.
Eight years of unmanaged SharePoint content
Marcus is the sole IT admin at a 180-person professional services firm. SharePoint has been running since the company was acquired by its current owner back when the tenant was set up, and nobody has ever run a storage audit. The Microsoft 365 admin center shows the tenant is sitting at 87% of its pooled storage quota. Three sites account for almost half of that.
He starts with ShareMaster's Report Master to get a file-level picture. Within an hour he has a spreadsheet listing every file across the three heaviest sites, with current size, version count, and total version storage for each item. The numbers are immediately clear: version history has grown completely unchecked. One project library has a 25 MB Word document with 812 versions, consuming over 11 GB on its own. Dozens of others have counts in the hundreds.
The actual business content, current files that people actively use, amounts to roughly 60% of the total storage. The rest is version history, orphaned project folders from finished engagements, and a video archive that was never cleaned up after a previous SharePoint migration years earlier.
What to clean up before migrating SharePoint
Before touching anything, Marcus draws a short checklist of what to address. Pre-migration cleanup typically falls into four categories:
- Version history bloat: excessive version counts on documents that are no longer actively edited. Safe to trim to a sensible keep policy (the last 10-20 versions).
- Orphaned project content: folders and libraries for finished projects where nobody will dispute deletion. Usually the highest-volume category.
- Large media files: videos, raw images, and presentation recordings that have been superseded or were never actively used. Easy to identify with a size sort.
- Duplicate uploads: files with identical names and near-identical sizes in different folders, often created by users syncing the same content from multiple devices.
Permission cleanup is a separate exercise from storage cleanup, but Marcus notes it for later: the acquiring company's tenant has stricter governance policies and he will need to present clean permission reports before the migration is approved.
"I thought the migration would be the hard part. It turned out the audit and cleanup took more decisions. Once we knew what we had, the actual move was straightforward." IT admin, professional services firm (paraphrased)
Running the cleanup with ShareMaster
Marcus uses Space Master's Version Trimmer on the three heavy sites first. He sets a keep policy of 20 major versions per file and no minor versions, previews the reclaim estimate (the tool shows exactly how much storage will be recovered before running), and runs the trim. It brings the total storage from 87% down to 61% of quota. The heavy Word document goes from 11 GB to under 500 MB for its 20 kept versions.
Next he uses Space Master's Bulk Delete tool to remove the orphaned project libraries. He exports the list of folders for review first, gets sign-off from the relevant project leads by email, then runs the bulk deletion. He removes seven old project libraries. Storage drops another 8 percentage points.
For the video archive he identifies files over 500 MB that have not been accessed in more than two years using the Report Master export, confirms with the original content owners that nothing needs to be kept, and deletes them. The remaining tenant storage is sitting at 48% of quota before the migration even starts.
He also runs a permissions audit using the Shared Links & Permissions tool. The audit surfaces 340 active shared links across the three sites, many pointing to project folders that are about to be deleted. He revokes the stale ones and documents the rest for the destination tenant admin.
See also: How to find large files in SharePoint Online for the step-by-step methods used in this audit phase.
Moving clean content to the new tenant
With a clean source, the migration itself is straightforward. Marcus uses ShareMaster's Clone Master to run the cross-tenant migration, moving sites, libraries, files, and permissions from the acquired company's tenant to the parent company's tenant.
Because the source was cleaned first, the migration scope is well-defined: 14 sites down to 10 active ones, storage at 48% of quota rather than 87%, and a permission set that has been reviewed and documented. Clone Master runs the migration overnight. A small number of items flag for manual review because of path-length issues in the destination tenant, but there are no quota errors and no stalled jobs from trying to migrate content that was going to be deleted anyway.
The destination tenant admin receives the migrated content with clean metadata, no version overruns, and a permissions summary she can work with from day one. The whole process, audit to migration complete, takes three weeks.
The lesson: the time spent on pre-migration cleanup is paid back directly in migration speed, cost, and quality. Every gigabyte of unnecessary content migrated is storage paid for in the destination, time spent transferring data, and a support ticket waiting to happen.
Frequently Asked Questions
How long does a SharePoint pre-migration cleanup take?
It depends on content volume and version history state. Generating a storage report takes minutes. Bulk-deleting stale content and trimming versions across a large tenant can take a few hours of tool work spread over a week of stakeholder sign-off decisions.
Should I clean up SharePoint before or after migration?
Before. Cleaning the source reduces migration time, lowers storage costs in the destination tenant, and avoids carrying years of orphaned content into a fresh environment. Cleaning after means paying to migrate content you were going to delete anyway.
Can ShareMaster migrate and clean at the same time?
ShareMaster's tools are complementary but separate. Space Master handles pre-migration cleanup: version trimming, bulk delete, empty folder removal. Clone Master handles the cross-tenant migration. Running Space Master first, then Clone Master, consistently produces the best results.