Deduplication typically targets either identical archive files (byte-for-byte) or duplicates within uncompressed content stored across archives. An archive (like a ZIP or RAR) contains one or more files compressed into a single container. Standard data deduplication software cannot directly remove duplicate files inside different compressed archives without first decompressing them. This is because the deduplication process analyzes unique data patterns that are obscured by the compression algorithms binding the files together. Some software may offer archive-aware deduplication by temporarily extracting files for comparison.

In practice, solutions that perform deduplication before data is compressed/archived are common. For instance, backup systems like Veeam or specialized storage appliances (e.g., Dell EMC Data Domain) often deduplicate individual files at the source before bundling them into an archive backup. Similarly, file archiving software managing a library of ZIPs might include deduplication features by extracting content internally during cataloging.

The main advantage is significant storage savings for redundant data across large collections. However, deduplication across compressed archives requires significant processing power to unpack them first, impacting performance and efficiency. Attempting byte-level deduplication on already compressed archives themselves is ineffective, as compression already removes redundancy; identical files compressed separately won't yield identical archive files, preventing detection unless the entire archive is identical. Future solutions may improve efficiency through smarter metadata handling but will likely still rely on extracting content for cross-archive deduplication.