This tool can be used online at the address http://lapo.it/asn1js/ or offline, unpacking the ZIP file in a directory and opening index.html in a browser
On the left of the page will be printed a tree representing the hierarchical structure, on the right side an hex dump will be shown.
Hovering on the tree highlights ancestry (the hovered node and all its ancestors get colored) and the position of the hovered node gets highlighted in the hex dump (with header and content in a different colors).
Clicking a node in the tree will hide its sub-nodes (collapsed nodes can be noticed because they will become italic).
WARNING: starting from 2023-02-26 this website is using some ES6 features, which can break it for older browsers (though it is still working on IE11).
You can access last version before ES6 on githack.
Copyright © 2008-2023 Lapo Luchini <email@example.com>
Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
OBJECT IDENTIFIER values are recognized using data taken from Peter Gutmann's dumpasn1 program.