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Drop one ZIP or two hundred. Batch conversion is not a paid feature here.
Convert ZIP to 7Z
A large archive is being put into long-term storage and the size actually matters.
SafeConvert engineFreeNo sign-upBatch supported
Waiting for files/Engine: on-device/Network requests made: 0
What actually changes
ZIP and 7Z are not the same picture in two wrappers.
The files are extracted and recompressed with LZMA2, using a dictionary large enough to find repetition across the whole archive rather than within a 32 KB window. Savings of 20 to 40 percent are typical.
Worth knowing first
The recipient needs 7-Zip or an equivalent, which no operating system ships by default. This is a format for archives you keep, not archives you send.
Questions
ZIP to 7Z, answered
Does recompressing lose anything?
No. Both formats are lossless. The files extract byte-identically.
How long does it take?
Much longer than ZIP. LZMA2 at a high setting is compute-heavy, which is the price of the smaller output.
How to convert ZIP to 7Z
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Choose your settings
7-Zip Archive is lossless, so nothing is thrown away in the conversion.
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Download
Converted and deleted the moment it finishes. Never written to permanent storage.