Performance
We compared 7-Zip with WinRAR 5.20.
FILE SETS: Mozilla Firefox 34.0.5 for Windows and Google Earth 6.2.2.6613 for Windows.
Compression ratio results are very dependent upon the data used for the tests.
Usually, 7-Zip compresses to 7z format 30-70% better than to zip format.
And 7-Zip compresses to zip format 2-10% better than most of other zip compatible programs.
Notes from this site
Not part of the 7-Zip manual. Written by this site; examples checked with 7-Zip 26.04.
Quick examples: faster, smaller, or measure it
The official Linux and macOS console program is 7zz; on Windows type 7z.
7zz a -mx=1 a.7z dir/ # fastest, larger archive
7zz a -mx=3 a.7z dir/ # fast, decent ratio: good for backups
7zz a -mx=9 a.7z dir/ # smallest, slowest, more RAM
7zz a -mx=9 -md=64m -mmt=4 a.7z dir/ # 64 MB dictionary, 4 threads
7zz a -mx=0 a.7z photos/ # store only: jpg, mp4, zip files
7zz a -mx=9 -md=16m -mmemuse=p50 a.7z dir/ # small server: less RAM
7zz b # benchmark this machine
# compare levels on your own data
time 7zz a -mx=1 t1.7z dir/ ; time 7zz a -mx=9 t9.7z dir/ ; ls -l t1.7z t9.7z
For large backups start with -mx=3 (the line above) and let 7-Zip use all cores. See -mmt and -mmemuse for the syntax, b (Benchmark) , and the 7z format page for the dictionary size of each level.
What to expect (one test machine)
On 100 MB of base64 text with a 12-thread Apple M2 Max: -mx=1 took 0.7 s and peaked at 60 MB of RAM, -mx=5 (the default) 9 s and 400 MB, -mx=9 20 s and 1 GB. -mx=5 is a sensible default; -mx=9 is rarely worth the extra time and RAM. Already-compressed data does not shrink: 2 MB of random bytes were 2,000,249 bytes at -mx=5 and 2,000,122 stored.
RAM and threads
The -m page puts LZMA compression at about 10.5 to 11.5 times the dictionary size, and decompression at about the dictionary size. So a smaller -md also lowers the RAM the recipient needs. In a one-thread test, -mx=9 -md=16m peaked at 198 MB instead of 1 GB, and testing the archive took 77 MB instead of 186 MB.
-mmt=N limits threads, not memory: one thread took 40 s instead of 9 s with about the same RAM. -mmemuse=p50 caps RAM at 50 percent; the manual says 7-Zip first reduces threads and still runs if it cannot fit.Reading 7zz b: each row is one dictionary size; the left half is compression, the right half decompression. The last line reads Tot: 1067 8005 85388 (usage %, R/U MIPS, rating MIPS on the test machine). Compare the last number between machines, run with the same options.
The table above
It compares 7-Zip 9.35 with WinRAR 5.20; today's 7-Zip defaults to LZMA2, so run your own test. A new 7z that comes out larger than an old one: see -mqs in the FAQ .