TAR to TAR.GZ
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 tar.gz around it.
The same archive, compressed. Nothing is lost.
This is gzip applied to the tar you already have, which is exactly what tar -czf does. Every permission, every link and every timestamp survives, because the tar itself is unchanged — it is just smaller. Typically a half to a tenth of the size, depending entirely on what is inside.
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 TAR.GZ 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
- TAR.GZ to TAR — the same conversion the other way
- TAR to ZIP — what everything opens without being asked twice
- JSON to CSV — for the data inside them