It's actually pretty terrible in practice. Keep in mind that most common tar files have also been run through a stream compression algorithm, which means scanni

It's actually pretty terrible in practice. Keep in mind that most common tar files have also been run through a stream compression algorithm, which means scanning the archive for file headers requires decompressing the entire thing. Some software does index tar files automatically (and of course the typical CLI tools will if you want) but for a large archive, say 20gb, I have had to stare at a progress bar for 30s+ while the tool indexed the archive. Extracting a single file required another 30s+ wait while it scanned the archive again to get back to that file, since with gzip compression it's not trivial to store enough state to be able to decompress at a point without having to decompress everything up to there.