Compare-ExportDelta¶

Diff two export runs and surface items that appeared, disappeared, or moved between tags. Part of the PurviewContentExplorerHelpers module - it reads two folders of per-tag CSV output and calls no Purview cmdlet.

Everything is derived from row data, never from filenames:

Item identity (the join key) is FileUrl (SPO/ODB), falling back to FileSourceUrl+FileName (EXO/Teams). The cmdlet's Location column duplicates Workload and is not an item identity.
Each item's tag set is the rows' TagType/TagName values (formatted TagType/TagName), so a renamed CSV is not reported as a change.

Synopsis¶

Compare-ExportDelta
    -Old <string>
    -New <string>

Parameters¶

Name	Type	Default	Notes
`-Old`	`string`	required	Folder containing the earlier export
`-New`	`string`	required	Folder containing the later export

Examples¶

Import-Module ./helpers/src/PurviewContentExplorerHelpers.psd1

# What changed between two monthly runs?
Compare-ExportDelta -Old ./output-2026-04/ -New ./output-2026-05/ | Format-Table

# Only items that lost or gained a tag
Compare-ExportDelta -Old ./output-2026-04/ -New ./output-2026-05/ |
    Where-Object Change -eq 'Reclassified'

Output¶

One PSCustomObject per changed item (unchanged items are omitted):

Property	Notes
`Item`	The item identity - `FileUrl`, or `FileSourceUrl` joined to `FileName` for EXO/Teams
`Change`	`Added` (only in new), `Removed` (only in old), or `Reclassified` (tag set differs)
`OldTags`	`TagType/TagName` values in the old export, comma-separated
`NewTags`	`TagType/TagName` values in the new export, comma-separated

Notes¶

Comparison is by tag membership, not row content - an item is Reclassified when the set of tags it appears under changes (for example it gained a sensitivity label or dropped a SIT match).
Item-identity and tag matching are case-insensitive, so URL- or name-casing drift between runs is not reported as a change.
The items_all.csv roll-up is skipped in both folders (it duplicates every per-tag row) unless it is the only CSV present. Files lacking the TagType/TagName columns and rows with no derivable item identity are ignored.