Compression decreases the size of data.

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76
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20answers
103k views

Compressing with RAR vs ZIP

A lot of people are compressing files with RAR, sending compressed files with RAR and so on. ZIP is more standard and works on all platforms. Windows users have ZIP included and Linux users have no ...
73
votes
8answers
97k views

What’s a good way to extract .rar files on the Mac? [closed]

Anything built-in? (E.g. command line tools.) Any well-regarded software? Update: I like The Unarchiver, but vote up your favourite, or add it as an answer if it isn’t there.
39
votes
5answers
35k views

Compressing folders on a mac, without the .DS_Store

Is there anyway to get rid of the .DS_Store when compressing a folder on a mac? I work on a mac and send work to clients in zip format, but always get questioned on the .DS_Store folder inside them. ...
13
votes
8answers
24k views

Why doesn't ZIP Compression compress anything?

A 398MB directory was only compressed to 393MB using 7Z and Normal ZIP compression. Is this normal? If so, why do people continue to use ZIP on Windows?
76
votes
5answers
86k views

How to specify level of compression when using tar -zcvf?

I gzip directories very often at work. What I normally do is tar -zcvf file.tar.gz /path/to/directory Is there a way to specify the compression level here? I want to use the best compression ...
43
votes
4answers
24k views

How does NTFS compression affect performance?

I've heard that NTFS compression can reduce performance due to extra CPU usage, but I've read reports that it may actually increase performance because of reduced disk reads. How exactly does NTFS ...
16
votes
4answers
40k views

What is the cause of a high CPU usage of 'system and compressed memory' in Windows 10?

There is an observation to be made for Windows 10 on my laptop running with 24G memory available, and 2.5G used. There is no 'memory pressure'. Other questions have looked at memory consumption (...
8
votes
6answers
2k views

Is there a free way to compress a PDF? [duplicate]

I have several PDFs that are quite large (one is 80+ MB). Is there a free way to compress that PDF to a smaller size?
1
vote
2answers
7k views

Compress a folder into multiple zip files

I'm on mac osx. 1. Is there any tool to compress a folder into multiple zip files ? 2. Is there any tool to split a compressed zip file into smaller zip files (to open individually later) ? thanks
5
votes
2answers
10k views

Convert old videos to have smaller sizes

I have some videos from a few years ago,with various formats, such as avi, mpg, wmv, rm, rmvb, .... Their sizes are huge(more than 500 MB, and sometimes > 1GB). Given there may likely be some ...
2
votes
5answers
9k views

How can I overwrite an existing file in 7zip?

I'm trying this: 7za.exe a "C:\Disc.7z" "C:\test" -v20000000b -m0=BCJ -bd But if I already have created the file C:\Disc.7z then 7zip doesn't compress anything and sends me this output: System ...
12
votes
9answers
37k views

Highest compression for files(for web transfer)?

I have seen some highly compressed files around, such as 700MB of data compressed to around 30-50MB. But how do you get such compressed files? I have tried using software like WinRAR and 7Zip but ...
16
votes
4answers
21k views

How to do “Files to store without compression” in 7-zip?

Is there any way to selectively prevent certain file types from compression in 7-zip, like in WinRAR? I'm trying to compress a huge folder (many gigabytes), and I don't want the already-compressed ...
20
votes
2answers
15k views

Is zip's encryption really bad?

The standard advice for many years regarding compression and encryption has been that the encryption strength of zip is bad. Is this really the case in this day and age? I read this article about ...
76
votes
5answers
42k views

Pros and cons of bzip vs gzip?

I've known gzip for years, recently I saw bzip being used at work. Are they basically equivalent, or are there significant pros and cons to one of them over the other?
23
votes
2answers
42k views

What do the numbers 240 and 360 mean when downloading video? How can I tell which video is more compressed?

I have downloaded some computer science lectures from YouTube recently. There is usually more than one choice of file size and file format to download. I noticed that for the same video, the ...
27
votes
3answers
50k views

Is it possible to execute a file after extraction from a 7-Zip self-extracting archive (SFX) archive?

I'm try to make a compressed deploy-able application. Currently I'm taking a set of files that I've published from my IDE (Visual Studio 2008 - WPF published application) and compressing ...
13
votes
6answers
25k views

How can I achieve the best, standard ZIP compression?

I don't care how long it takes to compress, all I want to achieve is two things: The absolute best possible compression ratio Compatibility with standard readers, such as Windows and WinZip So ...
16
votes
1answer
20k views

How does 'dictionary size' affect compression?

I know that higher size may lead to better compression ratio and vice verca. But is there a way I can decide better?.. since there are so many choices So far I've noticed dictionary size ≈ file ...
24
votes
6answers
3k views

How can I evaluate the best choice of archive format for compressing files?

In general, I've observed the following: Linux-y files or tools use bzip2 or gzip for distributing archives Windows-y files or tools use ZIP for distributing archives Many people use 7-Zip for ...
14
votes
4answers
47k views

What settings to use when making 7zip files in order to get maximum compression when compressing PDFs?

What settings to use when making 7zip files in order to get maximum compression? I'm compressing PDF documents containing scanned images. I'm thinking about using LZMA2, but I don't know what to set ...
6
votes
8answers
5k views

Winrar-like archive utility for OS X

I've been a Mac user for about 1.5 years and so far enjoyed the experience. But one thing I miss from other operating systems is the lack of compression/decompression utilities that follow the "folder"...
3
votes
3answers
3k views

How does the Windows 7 compression property weigh in against other compression methods?

I have a 1TB external hard drive of data that I have backed up from my main computer. To save space and give me the option of putting more data on this external HD, I'm considering compressing all of ...
3
votes
3answers
22k views

How can I remove the password protection from a RAR archive? [duplicate]

I have a directory in which there are lots of password protected .RAR files/archives. The passwords of these individual archives are known. I want to remove the password protection from all of them ...
2
votes
5answers
14k views

Is there a way to use the built-in Windows file compression tool on the command line?

Instead of using Right-Click/Send To/Compress (Zipped) Folder. I am using Windows Server 2003 Enterprise Edition.
0
votes
5answers
3k views

Does compressing files in XP slow things down?

I frequently run the Disk Cleanup tool and let it compress old files. However, one of the directories it compressed, full of small icon images, is terribly slow. Is this a result of the compression or ...
81
votes
11answers
4k views

Can zipping a file break it?

I just asked someone to send me a zipped psd file. They declined, citing that zipping a file can break the fonts. I assumed zipping a file is perfectly reversible, hence why it is commonly used. I ...
8
votes
2answers
5k views

How do I use the Google data compression proxy on Firefox?

I am using GNU Icecat (GNU version of Mozilla Firefox) on Trisquel GNU/Linux. In order to minimize/optimize data usage while web surfing, I want to use Google's data compression proxy. So, how do I ...
34
votes
5answers
7k views

Why is a 7zipped file larger than the raw file? [duplicate]

Possible Duplicate: Why doesn't ZIP Compression compress anything? I tried 7zipping an .exe file but it actually became larger. Is this the expected result?
9
votes
1answer
2k views

Hide NTFS compression blue double arrow icon overlay

Since the last Windows 10 update I have these blue double arrows on almost every item (all files & folders that are NTFS compressed). How can I remove these?
7
votes
5answers
6k views

How to open corrupted ZIP files?

How can I open (or repair) corrupted ZIP files on Windows? Is there a way to force 7-Zip to open them?
13
votes
4answers
8k views

How can I compress a file on Linux in-place, without using additional disk space?

I've got a 100GB drive that has a 95GB file. I need to free up some space on the drive (and right now transferring the file off the drive is not an option). The file would compress well with gzip or ...
13
votes
4answers
2k views

Why is a FLAC encoded from a decoded MP3 bigger than the MP3?

To be more precise than in the title, suppose I have a MP3 file that is 320 kbps. If I decompress it, then logically, all the data except for roughly 320 kilobits out of each second of audio should be ...
9
votes
4answers
2k views

Is there a compression or archiver program for Windows that also does deduplication?

I'm looking for an archiver program that can perform deduplication (dedupe) on the files being archived. Upon unpacking the archive, the software would put back any files it removed during the ...
6
votes
1answer
2k views

Compressing a file in place - does “gzip -c file | dd of=file” really work?

In the question How can I compress a file on Linux in-place, without using additional disk space?, one answer proposes to simply use gzip -c file | dd of=file I tried it (on Debian Linux), and it ...
18
votes
5answers
38k views

Windows Disk Cleanup: “Compress old files” option

Should I check "compress old files" option while performing disk cleanup on Windows XP? What are the pros and cons? Likewise, there is another option in Local Disk Properties window: "Compress drive ...
6
votes
3answers
6k views

Do encrypted compression containers like ZIP and 7-Zip compress or encrypt first?

The discussion of "compress and then encrypt, or vice-versa" led me to ponder the following question: many compression containers, like ZIP, 7z, and rar support encrypting these containers. For ...
3
votes
4answers
791 views

How to avoid compressing compressed files

Most compression programs compress all files by default. But when archiving a folder containing already compressed files, there is no need to compress them a second time, such as archives, packed ...
2
votes
2answers
2k views

Creating .xz with 7-Zip, claims insufficient memory (not true)

In WinXP 32bit with a Core i5 (dual core) and 4GB RAM, I'm trying to create an .xz archive from a 266MB log file using 7-Zip (GUI) on the "ultra" compression level (method: LZMA2, dictionary size: ...
0
votes
1answer
661 views

Is it possible to recursively list zip file contents with 7 zip without extracting

Similar to this question I have a very large zip file which contains other zip files, folders, and files. I want to use 7-zip to extract a list of file names from it, recursing into subfolders and zip ...
9
votes
4answers
1k views

More efficient file compression program for many identical files?

I am doing a backup of my work and I'm looking for a program that can more efficiently compress files. The windows default compression program works fine, but it doesn't work as "smart" as i would ...
5
votes
3answers
3k views

zip: Argument list too long (80.000 files in overall)

I need to compress 80.000 files into multiple zip files. This is the command I use: zip -s 200M photos_test/* However I get the following error: -bash: /usr/bin/zip: Argument list too long What ...
4
votes
4answers
7k views

Recursively unzip files where they reside, then delete the archives

I goofed up a setting on the backup software I use. Normally I would have the files from a network share get loaded into a spare drive, compressed into zip folders, then sent off to the offsite hub. ...
3
votes
2answers
2k views

How can I search for files that are either compressed or uncompressed in Windows Explorer?

I know that Windows explorer can colorize the NTFS compression state of a file, in both the regular and search views. How can I specifically filter/search for files that are compressed or ...
3
votes
4answers
1k views

Compress pdf file? [duplicate]

I need to reduce the size or compress a PDF file. The PDF file is actually scanned images. Is there any way by which I can compress the file?
3
votes
1answer
308 views

Why is the NTFS compression setting ignored by some applications?

I use NTFS compression on some folders, I understand the pros and cons of this, but for my use case it is preferred. I have noticed some odd behavior for many years. Some applications do not "honor" ...
3
votes
3answers
5k views

Why does a zip file appear larger than the source file especially when it is text?

I have a text file that is 19 bytes in size and having compressed the file using zip and 7zip, it appears to be larger. I had a read of the question on Why is a 7zipped file larger than the raw file? ...
3
votes
4answers
3k views

Windows: Will compressing the hard drive partition speed up disk access? [duplicate]

Possible Duplicate: How does NTFS compression affect performance? In theory, on a reasonably fast PC, the processor is mostly idle during hard drive access. A compressed file takes up less ...
2
votes
1answer
2k views

What does the number after 7-zip's -m switch mean?

7-zip has a command line switch to set the compression method, -m followed by a number, e.g. -m0=LZMA. What does the number (0 in the example) mean? Different numbers produce slightly different ...
2
votes
4answers
2k views

Good and free unzipping software for Mac? [closed]

What is a good and free unzipping software for Mac? Good as in...supporting different types of compressed files and can unlock password protected ones. The built-in one on Mac doesn't do a good job ...