Natural Potato Magnet


    3.6.14 • Public • Published



    Deduplicates and compresses a collection of website files and the resulting files must be interpreted with PHP.

    Intended to optimize storage space for static website archives using deduplication, and minification. Works particularly well for large generated websites that have been pulled with wget or curl. The resulting text files will retain their original file extensions but must be preprocessed with PHP. Text files already containing what could potentially be PHP code will not be changed. Binary files will be unchanged. You can control which of the files are just copied over (left unchanged).


    I wrote this because I restored a backup of an old vBulletin forum that I used to run. Not wanting to maintain the vBulletin software any longer I decided to simply generate a static version of the website, but found that it was several Gigabytes in size. Trying to deduplicate it manually was too difficult, so I wrote this module.


    This is a Node.JS module available from the Node Package Manager (NPM).

    Here's the command to download and install from NPM:

    npm install webarchiver -S


    In a Node.js module

    The easiest way is to just npm init a new project, and stick your website files in a sub-directory. Create your index.js file and put this in:

    var wa = require('webarchiver');
        files: "website/**",
        output: "archived"

    Where 'website' is the directory containing your files and 'archived' is the non-existent directory where the archive will be written.

    Now type node index.js and let it go to work.

    More Examples

    Finds more duplicates, but runs very slow:

    var wa = require('webarchiver');
        files: "website/**",
        output: "archived",
        passes: 3,
        dedupe: {
            minLength: 0,
            minSaving: 8,
            startsWith: ['<', '{', '\\(', '\\[', '"', "\\\\", '#', '\\.'],
            endsWith: ['>', '}', '\\)', '\\]', '"', "\\'", '\\n', '\\s', ';']

    Finds fewer duplicates, but runs faster:

    var wa = require('webarchiver');
        files: "website/**",
        output: "archived",
        passes: 1,
        dedupe: {
            minLength: 25,
            minSaving: 15,
            startsWith: ['<'],
            endsWith: ['>', '\\n']

    Finding too many duplicates can lead to poorer compression, see the Dedupe options and Performance sections for a discussion.

    Command line

    It is also possible to run it as a command like so:

    node ./node_modules/webarchiver --files "website/**" --output "archived"

    For array values, provide the option multiple times, e.g.: --files "pattern1" --files "pattern2" For dedupe and minify values just use a dot, e.g.: --dedupe.minLength 20

    • This might not accept HTML Minifier's regex options.


    This module exports all of its functions so you can potentially overwrite some parts of it! Some interesting ones are replacementAllowed which lets you reject a deduplication match, varCode which can alter the variable name used in the PHP output, and manipulations to perform one-time string manipulations. Simply use wa.functionName = function() { // your new code here }; before using wa.webArchiver... to overwrite functions. Similarly any variables used like this.variableName can be altered with wa.variableName = [your value];.

    If you just want the deduplicator logic you'll probably want to look at createFragments for preparing the string into a fragment array, fragmentMatches for finding duplicates (and look at how its used by findDuplicates), and doReplace for performing replacements on a fragment array (or use replaceAll with a string).


    You may override some or all of these options.

    Option name Type Description Default
    files string/array A glob pattern that indicates which files to process and output, or an array of glob patterns.
    output string The path of an output directory (doesn't need to exist yet) if options.inPlace is not used.
    justCopy string/array Glob pattern(s) of files (that are also found in 'files') to not process with compression but still output.
    inPlace bool If set to true will modify the existing files rather than creating new files. Not recommended.
    dedupe object/false Options to override deduplication behavior (or set to false to not deduplicate). (See below)
    minify object/false Options to override minification behavior as per the html-minifier package (or set to false to not minify). (See below)
    vFile string The name of the PHP variables file if 'v.php' is not acceptable. 'v.php'
    fullNest bool Whether to nest the full input path into the output directory. You shouldn't need this in most cases.
    skipContaining bool An array of strings; if a text file contains any of them the file will be treated as though it was matched in justCopy. ['<?']
    noProgress bool Set to true to disable the progress output.
    passes int Number of deduplication passes. Often things are missed on first pass. Can increase for extra dedupe checks. 2
    disable array Crude form element disabler, pass in something like ['button', 'input', 'options', 'select', 'textarea'].
    slugify bool Converts filenames of text files that contain an HTML title tag to SEO friendly slugs based on the title.
    slugifyIgnore array Array of strings to ignore from titles in the slugify process. See Extra features section.
    searchReplace object Custom search/replace to perform, e.g { search: ['chairman', 'cop'], replace: ['chairperson', 'police officer'], i: true }
    writeState bool Creates a file (state.json) at the end of processing containing the module's state (values of variables) and keep batches.
    batchDir string A directory to write out data for the purposes of batching large object collections and avoiding memory issues. 'wabatch'
    batchSize bool Size of the batches (in number of objects). 500

    Dedupe options

    Deduplication is performed on files that don't appear to contain binary data, aren't matched with options.justCopy, and don't contain strings in options.skipContaining.

    To speed up deduplication the file is analyzed in fragments where the fragments either start with a character in options.dedupe.startsWith, or end with a character listed in options.dedupe.endsWith. Multiple fragments may be joined together to create a duplication match, but no match will be smaller than a fragment. Deduplication is performed after minification to increase the chances of a match.

    The deduplication of the file is reconstructed on the server with PHP preprocessing. Therefore each file is prepended with a PHP include to a file with the replacement variables (options.vFile) and the contents of the file is echo'd as a PHP string. This works with HTML/CSS/JS files if they are set to be preprocessed by PHP on the server.

    Replacements are performed in the string by substituting portions of duplicated text with '.$var.' - where the names of the vars are automatically generated to be as short as possible. Therefore each file has some overhead (30+ chars**), each replacement instance has some overhead (3+ to 6+ chars*), and the storage of the original text has some overhead too (6 chars for the vFile header and 6+ chars* per string plus the length of the string).

    *The + refers to the fact that replacement variable names start out at a length of one character and increase in size as the program runs, the schedule for how many variables of each length are used is as follows:

    1: 26, 2: 936, 3: 33696, 4: 1213056 ... n: 36 ^ n - 10 * 36 ^ (n - 1)

    **30+ chars for file overheads because files inside directories can have ../ prepended to the include path to locate the file. The deeper the directory the more times ../ is inserted.

    Here is the full list of overheads:

    • 30+ char per file overhead: <?php include 'v.php';echo ' and ';
    • 6+ chars in typical replacement: '.$v.'
    • 3+, 4+, 5+ chars in adjacent replacement: .$v, $v., .$v., .$v.', or '.$v.
    • 6+ chars per replacement in vFile: $v='';
    • 6 char vFile header: <?php
    • 1 char per single-quote: i.e.: ' becomes \'

    Tip: You could be clever and cut out some overhead by using the auto_prepend_file, auto_append_file, and short_open_tag directives in php.ini then overriding the functions append, prepend, and perhaps createVarFile in this module to work with your system.

    Note: Further deduplication can happen that includes already deduplicated data, in this case replacements will be considered in their 6+ form even if they are adjacent replacements. This behavior seems desirable to me.

    Due to the overhead it is advisable to not choose a particularly small value for options.dedupe.minSaving. Setting options.dedupe.minLength to higher values will also speed up the algorithm, whereas using 0 will automatically calculate it each time based on minSaving and the 6+ typical replacement overhead (other overhead and occurrences are not factored in - you compensate for those by setting minSaving, and optionally minOcc, high enough). Setting minLength to greater than 0 but less than minSaving + 6 is a poor choice for computing efficiency. Bottom line though; both minLength and minSaving will be enforced no matter what you do here.

    The more chars added in options.dedupe.startsWith and options.dedupe.endsWith the slower the deduplication tends to go. At the minimum for HTML you should just use '<' and '>', but the braces, brackets, and parenthesis will help with JavaScript and CSS. Line breaks should be rare with minification so they may as well be included. Whitespace is included by default as it is quite an effective addition but does significantly hurt performance. Be aware that all chars are matched within the text of the website too (this module does not consider the DOM structure), and whitespace is particularly common in text. Adding semi-colon & single-quote to endsWith, dot & hash & backslash to startsWith, and double-quotes to both will give higher fragmentation and more potential to identify duplicates but noticeably slow things down.

    The following options are related to finding deduplication matches and performing deduplication replacements. The main options object contains configuration for additional deduplication behavior.

    Option name Type Description Default
    minLength int The minimum length a string of text must be to deduplicate. (0 = auto) 20
    minOcc int The minimum number of occurrences a duplicate must have to use it.
    minSaving int The minimum length of string minus the replacement instance overhead 10
    startsWith char[] Regex escaped chars that a fragment can start with. ['<', '{', '\\(', '\\[']
    endsWith char[] Regex escaped chars that a fragment can end with. ['>', '}', '\\)', '\\]', '\\n', '\\s']
    maxFileCompare int The maximum number of files to compare each file with (0 = all) 1000

    You may override some or all of these options at options.dedupe, your options will be merged into the defaults. You can set options.dedupe to false to disable deduplication.

    Warning: Do not add single-quotes to startsWith, use backslash instead ('\\\\') since single quotes are escaped. Conversely, don't add backslashes to endsWith.

    Minify options

    Minification is performed on files that don't appear to contain binary data, aren't matched with options.justCopy, and don't contain strings in options.skipContaining.

    Minification is performed by HTML Minifier. It handles HTML, CSS, and JS.

    Please see HTML Minifier's docs for a description of the options. Here is the default option object this module uses:

            collapseBooleanAttributes: true,
            collapseInlineTagWhitespace: true,
            collapseWhitespace: true,
            conservativeCollapse: true,
            html5: false,
            includeAutoGeneratedTags: false,
            minifyCSS: true,
            minifyJS: true,
            removeAttributeQuotes: true,
            removeComments: true,
            removeEmptyAttributes: true,
            removeRedundantAttributes: true,
            removeScriptTypeAttributes: true,
            removeStyleLinkTypeAttributes: true

    You may override some or all of these options at options.minify, your options will be merged into the defaults. You can set options.minify to false to disable minification.

    Extra features

    The module contains some quick and dirty features disabled by default which I needed for practical purposes to be able to configure the processing job to perform a few additional tasks on the files, so someone else might want them too. The features are all based on regex's, and along with minification the string changes are executed from the function manipulations prior to any deduplication.


    The option options.disable lets you pass in some tag names to which a disabled attribute should be added, this is intended to disable form elements in archives where the form-processing capabilities have been removed.


    The option options.slugify will convert filenames to more SEO friendly slugs based on the title tag. Additionally the option options.slugifyIgnore lets you pass in an array of strings to ignore from the title, it's common practice (although some argue it may hurt SEO) to remove words like: 'a', 'an', 'as', 'at', 'before', 'but', 'by', 'for', 'from', 'is', 'in', 'into', 'like', 'of', 'off', 'on', 'onto', 'per', 'since', 'than', 'the', 'this', 'that', 'to', 'up', 'via', and 'with'. More likely you'll want to use this to remove the title of your website from the filenames, e.g. [' -']. The original file extension will be retained.


    The option options.searchReplace will let you perform custom replaces on text files. A good use is to correct links that still point to old locations.

        searchReplace: {
            search: ['', 'showthread.php?t', 'forumdisplay.php?f', ''],
            replace: ['', 'showthread.php@t', 'forumdisplay.php@f', ''],
            i: true

    The 'i' key is a bool for case insensitivity.

    Why PHP?

    PHP is common, hosting is cheap, lots of people understand it, and syntactically it is quite succinct for our purposes. It seems like an ideal choice here. However, I am open to be convinced to support another method of preprocessing.

    While we're on the subject the PHP generated here is quite basic; Include and echo statements, variable assignment, and string concatenation. You should have no worries about which version of PHP to run.

    What else?

    You should also consider compressing your images. Many websites do not correctly compress their images, particularly older websites you may be archiving. There are several NPM packages you could use to automate this process, like imagemin.

    If you want to add custom HTML/JS/CSS to the files, for example to display a header that says "This is an archive" and link back to your site, etc... You could override the prepend/append functions, or use auto_prepend_file/auto_append_file directives in php.ini.


    I have some more ideas for this package which I may pursue:

    • Pull down remote websites to archive. Currently it only works on static files you already have.
    • Extract contents of style and script tags into separate files. This would allow them to be cached client-side.
    • Perhaps integrating image compression, and using magic number filetype detection in case the extension is wrong (it was common for image data to be served from PHP or Perl, or for webmasters to use bogus image extensions to bypass hosting limitations, and finding these can be a problem without automation.)


    By the way here is the command I used to rip the vBulletin site down to my hard drive:

    wget -r http://website.address/directory --convert-links=on --html-extension=on --page-requisites --accept '*.html,showthread.php*,forumdisplay.php*,member.php,images*,*.gif,*.png,*.jpg,*.jpeg,*.css,*.js,clientscript*' --reject "*?p=*,*goto=*,*sort=*,*order=*,*daysprune=*"

    Perhaps that could help someone.


    With just a few hundred files the operation is relatively quick. Each file must be deduplicated against all of the files that came before, therefore the performance complexity of each file is greater than the previous file.. On the flip-side, as more deduplication replacements are made, the previous files become smaller and faster to check. Nevertheless processing thousands of files, gigabytes of data, will require some patience.

    A performance test is available in the github repo and can be executed with npm run performance. This data set contains a high number of duplicates to really run this thing through the wringer.

    # Files Size Config Time Output size
    250 15 MB minLength = 0 10.4 minutes 2.48 MB
    250 15 MB minLength = 20 9.4 minutes 2.49 MB
    500 30 MB minLength = 0 26.9 minutes 2.92 MB
    500 30 MB minLength = 20 25.6 minutes 2.91 MB

    This shows how setting minLength to 0 (auto) is slower and can even result in worse compression than setting a higher value. It also shows that doubling the amount of data to process leads to MORE THAN double the processing time. The variables in the performance tests can be tweaked to test other conditions.

    In earlier test cases, with a different set of files, I could run 1000 files through in 2.5 minutes. So it's difficult to predict how a particular job will perform, so consider these values relative to each other rather than as a guide to how long things will take, or how much compression will be achieved.

    Performance in the wild varies greatly based on machine specs, file contents, and configuration options.

    FYI this module currently does a lot of synchronous operations and isn't intended to run in a live production environment. If there's interest to change that then that's something else that could be looked at.

    See the Dedupe options section for a better understanding of the pressure points regarding balancing performance and deduplication effectiveness, and some configuration ideas for striking the right balance for you.


    Tests are available in the github repo and can be executed with npm test.

    To check coverage you have to install istanbul globally: npm install istanbul -g and then execute: npm run coverage A coverage summary will be displayed and a full coverage report will appear in the /coverage directory.


    In lieu of a formal style guide, take care to maintain the existing coding style. Add mocha tests for coverage and explicitly test bugs.


    npm i webarchiver

    DownloadsWeekly Downloads






    Unpacked Size

    60.5 kB

    Total Files


    Last publish


    • braksator