What does this tool do?

It decodes DER or BER hex with decodeAsn1 into tagged nodes with depth, byte ranges, typed values, children, and a hex dump table.

How are OIDs, times, and BER handled?

OIDs render as dotted arcs like 1.2.840.113549.1.1.1, UTCTime converts to ISO with the raw text, and 0x80 indefinite lengths decode constructed values up to the 00 00 terminator.

Is my binary uploaded or stored?

No. Hex parsing and ASN.1 tree building run fully client-side.

Why a truncated or indefinite-length error?

Cut-off tags, lengths, and values throw offset-stamped errors, and indefinite length on a primitive tag throws because only constructed values may use it.

ASN.1 DER/BER Decoder

Inspect Tag-Length-Value bytes locally with a recursive tree and hex dump

Hex input

DER / BER bytes

Spaces, commas, colons, hyphens, and 0x prefixes are accepted.

Paste hexadecimal DER or BER bytes to inspect recursive SEQUENCE and SET structures, decoded OIDs, signed integers, UTC times, and an offset-based hex dump.

About this tool

Inspect ASN.1 Tag-Length-Value structures, OIDs, integers, UTC times, offsets, and BER indefinite lengths locally. ASN.1 DER/BER Decoder runs in the browser on DevTools. There is no signup, and your input stays on this device unless the tool explicitly performs a live network lookup.

What this tool does not do

ASN.1 DER/BER Decoder is a free in-browser utility, not a hosted API. It does not keep server-side history and is not a substitute for production verification in your own stack.

How do I use this tool?

How do I use ASN.1 DER/BER Decoder?
Open ASN.1 DER/BER Decoder, enter or paste your input, and copy the result. The page works without an account.

Proto, JS AST, GeoJSON, ASN.1 & Parquet Inspectors

Parse .proto files into queryable ASTs, visualize JavaScript syntax trees, quantize GeoJSON to TopoJSON, decode ASN.1 TLV bytes, and preview Parquet.

.env Secret Safety Linter

Validate .env syntax and spot likely leaked credentials or placeholder secrets.

.htaccess Generator

Build an Apache .htaccess — HTTPS redirects, rewrites, error pages, security headers, and basic auth

2D Fluid Dynamics & Particle Physics Sandbox

A physics playground with two engines sharing one canvas. The fluid mode runs a real Eulerian Navier-Stokes solver — semi-Lagrangian advection, explicit diffusion, Jacobi pressure projection and vorticity confinement — that you paint with dye and velocity using mouse or touch. The particle mode is a damped Verlet N-body engine with gravity wells, Coulomb attractors and repulsors, spring links, wall restitution and elastic circle collisions. Particle counts adapt to the device (100k target on WebGL2 desktop, 2k-5k on CPU fallback), and every configuration exports as runnable code: a Matter.js world, a PixiJS ticker setup, or a standalone vanilla Canvas engine.

AI Function Calling Schema Generator

Generate function calling JSON schemas from TypeScript interfaces

Algorithm Arena & Data Structure Visualizer

Interactive arena for algorithms and data structures: eight sorting algorithms racing on one seeded input, six pathfinding algorithms walking generated mazes, and BST, AVL, Red-Black, B-tree, heap and trie operations replayed step by step with rotations highlighted. Every run shows the Big-O table and the phase-highlighted reference implementation in four languages, and compared values can be played as pitch (sonification) through the shared audio engine. Everything runs client-side; inputs never leave the browser.

Ansible Playbook Generator

Build an Ansible playbook — hosts, vars, and tasks with modules — as YAML