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hexdump, binary pretty-printing

build status # hexy.js -- utility to create hex dumps

hexy is a javascript library that's easy to use to create hex dumps. It works well in node and has cursory browser (more below) support. It contains a number of options to configure how the hex dump will end up looking.

It should create a pleasant looking hex dumb by default:

var hexy = require('hexy'),
       b = new Buffer("\000\001\003\005\037\012\011bcdefghijklmnopqrstuvwxyz0123456789")
        // or String or Array containing numbers ( bytes, i.e. < 0xFF )


results in this dump:

00000000: 0001 0305 1f0a 0962 6364 6566 6768 696a  .......bcdefghij
00000010: 6b6c 6d6e 6f70 7172 7374 7576 7778 797a  klmnopqrstuvwxyz
00000020: 3031 3233 3435 3637 3839                 0123456789

but it's also possible to configure:

  • Line numbering
  • Line width
  • Format of byte grouping
  • Case of hex decimals
  • Presence of the ASCII annotation in the right column.

This means it's easy to generate exciting dumps like:

0000000: 0001 0305 1f0a 0962  .... ...b 
0000008: 6364 6566 6768 696a  cdef ghij 
0000010: 6b6c 6d6e 6f70 7172  klmn opqr 
0000018: 7374 7576 7778 797a  stuv wxyz 
0000020: 3031 3233 3435 3637  0123 4567 
0000028: 3839                 89

or even:

0000000: 00 01 03 05 1f 0a 09 62   63 64 65 66 67 68 69 6a 
0000010: 6b 6c 6d 6e 6f 70 71 72   73 74 75 76 77 78 79 7a 
0000020: 30 31 32 33 34 35 36 37   38 39

with hexy!

Accepted Input

Currently, input should be one of the following:

  • a Buffer
  • a String
  • an Array containing Numbers. These should fit into 8 bits, i.e. be smaller than 255. Larger values are truncated (specifically val & 0xff)

Formatting Options

Formatting options are configured by passing a format object to the hexy function:

var format = {}
    format.width = width // how many bytes per line, default 16
    format.numbering = n // ["hex_bytes" | "none"],  default "hex_bytes"
    format.format = f    // ["fours"|"twos"|"none"], how many nibbles per group
                         //                          default "fours"
    format.caps = c      // ["lower"|"upper"],       default lower
    format.annotate=a    // ["ascii"|"none"], ascii annotation at end of line?
                         //                          default "ascii"
    format.prefix=p      // <string> something pretty to put in front of each line
                         //                          default ""
    format.indent=i      // <num> number of spaces to indent
                         //                          default 0
    format.html=true     // funky html divs 'n stuff! experimental.
                         //                          default: false

console.log(hexy.hexy(buffer, format))

In case you're really nerdy, you'll have noticed that the defaults correspond to how xxd formats it's output.


Either use npm:

npm install hexy

This will install the lib which you'll be able to use like so:

var hexy = require("hexy"),
    buf  = // get Buffer from somewhere,
    str  = hexy.hexy(buf)

It will also install hexy into your path in case you're totally fed up with using xxd.

If you don't like npm, grab the source from github:

Browser Support

Basically eveything should work fine in the browser as well, just include hexy.js in a script tag, and you'll get hexy and Hexy stuck to the global object (window).

Some caveats: "Works fine on my systemâ„¢". Browser support is 'new' and not thoroughly tested (... eh, only on chrome [Version: whatever I'm currently running]). Under node, I can generally assume that binary data is passed in in a sane fashion using buffers, but plain old Javascript doesn't really have any datatypes that can handle bytes gracefully. Currently only Strings and arrays containing Number'ish values are supported, I'd like to add numeric and typed arrays more explicitly.

Let me know in case you run into any issues, I'd be happy to find out about them.


The current version only pretty prints node.js Buffers, and JS Strings and Arrays. This should be expanded to also do typed arrays, Streams/series of Buffers which would be nice so you don't have to collect the whole things you want to pretty print in memory, and such.

I'd like to improve html rendering, e.g. to be able to mouse over the ascii annotation and highlight the hex byte and vice versa, improve browser integration and set up a proper build & packaging system.

Better testing for browser use.


  • Thanks to Isaac Schlueter [isaacs] for gratiously lending a hand and cheering me up.
  • dodo (
  • the fine folks at Travis
  • radare (
  • Michele Caini (


This is a fairly straightforward port of hexy.rb which does more or less the same thing. You can find it here:

in case these sorts of things interest you.


In case you discover bugs, spelling errors, offer suggestions for improvements or would like to help out with the project, you can contact me directly (