What Is a Zip File? Meaning, Working, and Advantages

• A Zip file is an archive file format with the .zip extension that can contain one or more files or directories for storage or for the dual purpose of compression and storage
• Using Zip files helps to reduce a directory or file size in a lossless manner. 
• This article explains the working, advantages, and disadvantages of using a Zip compression system.

What Is a Zip File?

A Zip file is defined as an archive file format with the .zip extension that can contain one or more files or multiple directories of files either for storage or for the dual purpose of compression and storage to reduce the file’s size in a lossless manner. 

Reference image:

Image source: GoAnywhere Opens a new window

A diagrammatic representation of how a Zip compression works. 

Compressing files is an essential component of the digital workplace, allowing users to save time, resources, and effort. Zip files employ compression to deliver more data at a faster rate than would be feasible without compression. This explains why this is such a popular commercial tool across the globe.

Zip is a commonly used file format for compressing several files into a single place. This decreases file size and facilitates transfer and storage. After delivery, a receiver may unpack (or retrieve) a Zip file and utilize it in its original format.

Zip files function similarly to standard folders on your computer. They hold data and files in one location. However, the contents of zipped files are compressed, decreasing the data your computer requires.

Usually, file compression operates by analyzing the entirety of a file, recognizing identical or repetitive patterns and data, and substituting duplicates with a unique ID. This identifier is often much smaller than the original items and requires less space. Consequently, the compressed file is significantly smaller in size. We describe precisely how file compression happens in this guide.

The alternative term for Zip files is an archive. The archive stores compressed files in a single place. Therefore, the Zip file type offers an alternative for compressing a file or a collection of files.

The most prevalent application for Zip files is software downloads. The zipping of a program saves space on the computer network, reduces the time required to transfer it to a machine, and maintains tens of thousands of files structured inside a single file.

Another instance is downloading or distributing hundreds of graphic-heavy documents, such as presentations. Instead of sending each picture separately through email or downloading each image from the website, the user may place the images in a Zip package so that the user must transfer just one file.

Understanding the Zip format

Zip is a lossless compression, decompression, and archiving format designed by Phil Katz in 1989 and initially implemented by PKWARE’s PKZIP.

Eventually, the Zip file format specifications were released to the general public, and the format enjoyed enduring popularity. As a result of its overwhelming popularity, the term “zip” is now often used to refer to any generic compressed archive, and numerous packaged types are based on very similar capabilities. This covers Java JAR/WAR/EAR, Android APK, iOS IPA, Microsoft CAB, and Office compound files.

At its core, the Zip format uses many different compression algorithms (a concept we discuss next). The most notable ones include the following:

• Store without compression
• Shrink using the LZW algorithm (a method for global lossless data compression developed by Abraham Lempel, Jacob Ziv, and Terry Welch)
• Reduce at levels between 1 and 4 using the LZ77 algorithm (1977 publication of a lossless compression technique by Lempel and Ziv)
• Deflate algorithm (a lossless data compression file format containing a series of blocks), which is the most common one

Zip files may also support Implode, Deflate64, bzip2, LZMA, WavPack, and PPMd, among other compression formats.

In 2009, WinZip 12.1 announced the brand-new ZIPX file format standards, which specify a newer archive specification that allows more advanced compression methods.

Alternatives to Zip files

Multiple alternative archiving standards, including ARJ, RAR, ACE, and 7Z, have evolved during the 1990s. The addition of these features enhances traditional Zip files.

• Typically, they have a higher ratio of compression than Zip files. This may need slower operation, but the trade-off is decreased transfer times, particularly on sluggish and public networks.
• They provide multivolume archiving. They may stretch the output to several files to accommodate limitations such as the maximum size of email attachments.
• Error detection and repair are mandated, such as in the ARC and RAR file formats. This inhibits extraction if data becomes corrupted (for example, a defective connection or a damaged disc) and enables you to try restoration from verified accurate data.

Additional options for standards offer users more functionality and intense competition. However, it also requires archive software that can decompress several formats and serve multiple purposes.

Recently, users have shifted towards more efficient and rapid compression methods. These are designed to reduce data transfer decompressing and compression costs and attain speeds close to real-time. Google’s Brotli (BR file format) and Facebook’s Zstandard (ZST file format) are two of the next-generation algorithms that provide a better alternative to Zip files. 

Let us look closer at compression algorithms that form the basis of technology like Zip files.

What is a compression algorithm?

Typically, compression techniques decrease file size without losing any information. This may improve the files’ entropy and make them appear more random since all conceivable bytes become more frequent. This makes them essential to the file compression process.

• Masking: One of the most common algorithms used for file compression is the mask or disguise compression algorithm. It often generates data that appear random. That is, the data distribution is more uniform.
• Security: Most compression methods broadcast the tables or dictionaries at the beginning of the file. Although this is optional, it is recommended if all parties can settle on a specific table in advance. It is a common practice that may jeopardize security. That is why encryption is necessary, along with file compression. Notably, that is why Zip files come with the ability to add password protection.
• Usage: There are a variety of compression applications available for all PCs. They frequently employ proprietary algorithms which are superior to open-source alternatives.

See More: An Introduction to AI-Based Video & Image Compression 

How File Compression Works

File compression is essential to the operation of the web. It enables transporting files that would typically use excessive bandwidth and time. When you read Zip files or see JPEG photos, file compression is at work in such cases. 

A compressed file is an archive that includes one or more files with decreased file sizes. Because these files are compressed, they need less storage space and may be sent over the internet faster. Users may unzip the files to their original, unaltered condition using a specialized application like WinZip or similar software.

Most computer file formats are primarily redundant; they include repeated listings of the same information. Simply, file compression algorithms eliminate redundancy. Instead of repeatedly displaying the same information, a file-compression software lists it and then links it wherever it occurs in the original program. Here’s how this process takes place:

• Dealing with redundancy: Most compression tools use a variant of the adaptive dictionary-based LZ algorithm to compress files. “LZ” refers to the algorithm’s founders, Lempel and Ziv, and “dictionary” is the method of categorizing data items. The procedure for organizing dictionaries varies, although a simple numbered list may suffice. It extracts the repeated words (or datasets) from a file and places them in the numbered index. Then, it merely writes a number rather than the whole word.
• Finding patterns: Based on the file format, the compression tool may or may not use the idea of distinct words; it may also search for patterns. And, to reduce file size to the greatest extent possible, it picks dictionary patterns with care. The software iterates over the file, extracting all repeated pieces of information and then determining which patterns should be written to the dictionaries and index via numbers.

In most languages, some characters and symbols often occur in tandem. Due to the high incidence of duplication, text files condense very efficiently. A decrease of at least 50% is usual for text files of adequate size.

Typically, if a file has several repeating patterns, the reduction rate rises with file size. Nevertheless, its effectiveness partly relies on the method employed by the compression software.

Even though all compression programs operate using the same fundamental principles, there is a great degree of difference in how the algorithms are implemented. Some applications are especially adept at recognizing patterns in particular types of files and can therefore compress them more efficiently. Others have dictionaries inside dictionaries, which may compress well for bigger files rather than for smaller items.

Typically, compressed file extensions are .zip,.sit, and .tar. These are file extensions denoting various compression formats, i.e., file compression software. The most prevalent file extension for Windows PCs is.zip, .sit is often used on Macs, and .tar is used on Linux.

How do lossless and lossy compression work?

Compression may be either lossless or lossy, with the latter not always resulting in decreased quality or usability challenges. Let’s examine how each compression approach works:

• Lossless file compression: Lossless compression rebuilds and restores file data to its original state after decompression. For instance, when the file size of an image is condensed, its quality stays unchanged. Without data loss, one may resize the file to its original state. This kind of compression is often referred to as reversible compression.

Even if file sizes are decreased using this approach, the reduction is smaller than with lossy compression. Lossless file compression uses techniques like Run Length Encoding, Lempel-Ziv-Welch (LZW), Huffman Coding, or arithmetic encoding. As discussed, Zip files are lossless in nature. 

• Lossy file compression: In lossy compression, data is stripped from a file and is not returned to its original state upon decompression. Specifically, data is erased irreversibly, which is why this technique is also called irreversible compression. Such data loss is often imperceptible. Nonetheless, the longer a document or file has been compressed, the more deterioration happens, and the loss becomes evident over time.

Lossy compression significantly decreases file size in comparison to lossless compression. Standard lossy file compression methods are transform coding, discrete cosine transform, or fractal compression, which are not used in Zip files.

No “correct” or “best” alternative exists when deciding between lossless and lossy compression. The selection varies depending on the usage, the amount of quality loss that is acceptable, and the required file size.

Therefore, any blog or website might gain from lossy compression as it significantly reduces file size, conserves storage space, and enhances site speed and user experience. A website that demands high-quality photographs or an archive of essential documents in a Zip file might benefit more from lossless compression.

Using both file compression methods inside the same program is also feasible.

See More: What Is Data Analytics? Definition, Types, and Applications

Advantages of Using Zip Files

Users have relied on Zip files for over 30 years for file compression, sharing, and management. This is due to the many advantages it offers:

1. Simplifies storage

One benefit of Zip files is their storage and organizational capabilities. If you have many files that you do not intend to use in the near future, you may “zip” them all into a single package. This will reduce their size and arrange them into a single file that is easy to locate and utilize. Some files in your company may be pretty huge; therefore, compressing a number of them into a unified zipped file may significantly decrease the storage space required and the difficulty of finding them.

2. Enables portability

Transferring a compressed file to a blank CD or universal serial bus (USB) flash device is also beneficial. Since the compressed file is compact, one can add far more data to the storage medium than possible, and transferring data takes less time. If users zip all items this way, you can fit significantly more data on the CD than if they had not attempted to compress them. This also contributes to long-term cloud storage cost savings.

3. Bypass email attachment constraints

Another benefit is that it is simpler to transmit Zip files. A compressed file inside an archival system will be more compact than the original one. It is also a single file since one may compress several files. This makes it much simpler to transmit the compressed file as attachments through email much simpler, particularly considering that certain email services have a maximum file size restriction. Therefore, sending a file in compressed format is possible, which would not be feasible otherwise.

4. Streamline backups

Many data backup software applications generate file duplicates in the Zip format. The files are compacted to conserve space, grouped for quicker retrieval, and preserved in a standard format to ensure one can access the backup regardless of the originating backup software. COMODO Backup is an application that does this task using Zip files.

5. Conserve resources

Suppose you have many files on your computer but have yet to make plans to access them (a common occurrence for auditors, web developers, and other specialists who manage multiple file versions). It is not practicable to leave them on a hard disc drive (HDD) or solid-state drive (SSD). Charges would skyrocket if you kept this information on the cloud. Alternatively, you can Zip many documents into a single archive folder, which frees up storage space and simplifies categorization.

6. Enjoy searchability

Although compression files may discard some data, a Zip file retains all data and enables searching for specific words, phrases, or file kinds inside the folder. Using such a Zip file for preservation may help you organize your papers and make it easy to identify specific items. Because zip files include the original information (or other contents), anyone can employ them as archives to recover older versions of your files.

Potential disadvantages of Zip files

Despite these substantial benefits, there are some possible drawbacks connected with Zip files. There are limitations on file size, file type, corruption, and mobility.

One is compression limitations — certain files can’t be compressed more than they are currently zipped. This is particularly true with MP3 and JPG files. Therefore, if you often deal with video and picture files, using Zip format will not save you significant space.

Users must also think about the safety aspect of compressed data. You should evaluate exactly what happens to a file when you transfer it to a third-party application for compressing. It is also important to note that .zip extensions might get damaged. In rare instances, data corruption might damage the whole Zip folder.

Additionally, Zip files are tough to utilize while traveling. You must combine a locally stored file and a third-party application using a smartphone or tablet. This could prove problematic with both file storage capacity and cybersecurity.

See More: What Is Version Control? Meaning, Tools, and Advantages

Takeaway

Zip files are one of the oldest methods used for compression. In the 1990s, it replaced the ARC file format used in the days of dial-up internet, mainframes, and early computers. Zip files have evolved, introducing new and better algorithms that can compress files without noticeable loss to quality or user experience. Some programs even allow users to live-edit the contents of a Zip file, overcoming the last hurdle for file compression and archival. 

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