It depends a lot on what options you've given
wget on the commandline. I've found that the default behavior on my systems is to re-download, but append a number to the filename to make it different.
--no-clobber option description from
man wget (for wget 1.11.4) -- note the interactions with other options, particularly
-p. (Emphasis mine.)
If a file is downloaded more than once in the same directory, Wget’s
behavior depends on a few options, including -nc. In certain cases, the
local file will be clobbered, or overwritten, upon repeated download. In
other cases it will be preserved.
When running Wget without -N, -nc, -r, or p, downloading the same file in
the same directory will result in the original copy of file being preserved
and the second copy being named file.1. If that file is downloaded yet
again, the third copy will be named file.2, and so on. When -nc is
specified, this behavior is suppressed, and Wget will refuse to download
newer copies of file. Therefore, ""no-clobber"" is actually a misnomer in
this mode---it’s not clobbering that’s prevented (as the numeric suffixes
were already preventing clobbering), but rather the multiple version saving
When running Wget with -r or -p, but without -N or -nc, re-downloading a
file will result in the new copy simply overwriting the old. Adding -nc
will prevent this behavior, instead causing the original version to be
preserved and any newer copies on the server to be ignored.
When running Wget with -N, with or without -r or -p, the decision as to
whether or not to download a newer copy of a file depends on the local and
remote timestamp and size of the file. -nc may not be specified at the same
time as -N.
Note that when -nc is specified, files with the suffixes .html or .htm will
be loaded from the local disk and parsed as if they had been retrieved from