Compression in Browser

It is often a goal to compress web pages so that they take less bandwidth, less hard drive space, and are difficult for people to reverse engineer. This has been called “compression,” but it is more along the lines of consolidation, and minification is a far better term. The process typically removes whitespace, removes comments, replaces names with shorter ones, and reworks the structure so it takes less space. Few solutions perform actual compression of the information.

What I present here is not an ideal solution. Compression of this kind is far better done at the server; if your server can compress data in transit, the browser will decompress it using native code and the compression will be significantly better. The output generated on this page is more appropriate when you need to serve data from file:// URIs, such as documentation on a CD. Another alternative is to bundle your site into a .jar file, because that format has built-in compression.

From time to time, I feel like taking on the challenge of making compressed web pages. Anything that seems remotely successful, even for a specialized use, is included. You can use this to compress your web pages and text as long as JavaScript can be used to decode the information. Copy your HTML or text into the correct box and use the button to compress.

LZ77

This algorithm operates by walking through the original text and seeing if the characters at the current position are a repeat of something earlier. If they are, it encodes where the earlier copy starts and how many characters to copy.

The technique, published by Abraham Lempel and Jacob Ziv in 1977, is a “sliding window” compression algorithm, which is a type of dictionary coder.

Huffman Encoding

This recodes letters, giving shorter codes to frequently used letters. For instance, English text is typically lowercase letters, and the most common letter is “e”. By analyzing the text that will be compressed, the program figures out how often each letter is used, arranges the letters into a tree, and then determines the new codes.

Base64 Encoding

Technically, this is not compression. Instead, it is a way of taking binary data and changing it to a text-only form. The encoding increases the size of the information by 33% and is the method by which email attachments are sent.