TAR to ZIP
Nothing you choose here leaves your browser, and nothing is downloaded to make it work — not a library, not a compression module, nothing. Your browser already knows how to deflate and gzip; this page writes the ZIP around it.
This is the conversion that loses something, and it is worth knowing what.
A tar records the permission bits, the owner and the group of every file, and can hold symbolic links and devices. A ZIP has nowhere to put ownership and cannot hold a link at all. Everything that will not fit is listed on screen before you download, rather than quietly dropped — which is how people find out a month later that nothing is executable any more.
How this works, and why nothing is fetched
Your browser already knows how to deflate and gzip, because it needs both to load web pages. This page uses that through CompressionStream and writes the ZIP structure around it. Nothing is fetched, nothing is installed, and your files never leave the machine.
What it will not do
It will not open a RAR, and nothing ever writes one: RARLAB's licence forbids using their code to re-create the RAR algorithm, which is proprietary. That is a legal restriction and not a difficulty. It will not open a 7z, bzip2 or xz either — those need compressors your browser does not have, so supporting them would mean shipping one, which is the thing this page avoids. It says which of these it is looking at rather than just refusing.
It does not open password-protected archives, and it says so per file rather than failing silently. It reads plain ZIPs rather than ZIP64, so an archive over 4 GB or with more than 65,535 files is refused with that reason given.
Where to go next
- ZIP to TAR — the same conversion the other way
- TAR to TAR.GZ — the Unix default, small and lossless
- JSON to CSV — for the data inside them