System
URL Session Cache
macOS stores background download and upload cache data for NSURLSession in com.apple.nsurlsessiond, the system daemon that handles URLSession tasks for apps even when they are suspended. This cache can include HTTP response bodies, cached headers, partial download fragments, resume data, and metadata used to continue transfers and avoid re-downloading unchanged content. Kudu removes those temporary URL Session cache files so stale network artifacts are cleared without touching app documents, accounts, passwords, or saved settings.
Why clean URL Session Cache?
- Corrupted resume data for interrupted downloads can make a transfer repeatedly fail or restart from the beginning instead of resuming normally
- Stale cached HTTP responses and headers can cause apps to show outdated content, missing updates, or old thumbnails until the cache is rebuilt
- Bad partial download fragments in nsurlsessiond can leave an app stuck on waiting, preparing, or endlessly spinning while the daemon retries the same task
- Oversized URLSession disk caches consume space in ~/Library/Caches and show up as unexplained system or app cache growth even after the original files were removed
- Expired or mismatched cache metadata can trigger repeated revalidation requests, making feeds, sync jobs, or background refresh feel slow despite a working connection
- Apps that rely on background URLSession transfers may appear unable to finish downloads after sleep or reconnect because the daemon is reusing broken cached state
- Fragmented cache databases and metadata stores can accumulate dead pages over time; vacuuming rewrites the SQLite file compactly without deleting live rows, reducing wasted space and occasional lookup slowdowns
What gets cleaned
Cache paths Kudu targets
macOS
~/Library/Caches/com.apple.nsurlsessiond |
Frequently asked
Common questions about URL Session Cache
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