OneDrive Files On-Demand shows cloud files as placeholders. Indexers may list them, open fails offline, users blame search.
Sync clients mirror paths locally but the layout is weird and placeholders confuse indexers. Here's how I set exclusions so search stays fast without missing synced docs.
Index hydrated files only
Pin important folders for local copy, or exclude sync root and index a local Projects mirror you control. Know what's actually on disk.
Duplicate paths and moved folders
Same repo synced and cloned to Git — two paths one file. Exclude one path from index to avoid duplicate hits. Dropbox, Google Drive, iCloud follow the same rules: re-point the indexer when a sync client migrates its directory after an update.
See also: When not to index a folder, Search across multiple drives without the lag.