TLV Tree Visualizer
Visualise BER-TLV / EMV TLV bytes as a collapsible nested tree with tag-name lookup. The visual companion to the existing TLV parser, focused on hierarchy.
How to use this tool
What it does
Renders nested BER-TLV as an expandable tree, showing how constructed objects contain primitive ones.
When to use it
Use it when a record nests templates several levels deep and a flat list is hard to follow.
Worked example
Expand a 0x70 template to see the primitive tags it wraps.
Input
Tree
About TLV
BER-TLV (ISO 7816-4 / EMV) encodes structured data with Tag, Length, Value triples. Tags can be primitive or constructed; constructed tags contain nested TLVs. EMV uses BER-TLV throughout the contact and contactless protocols.
Spec
ISO/IEC 7816-4 §5.2; EMV Books 3 + 4.
Companion
BER length calculator · TLV parser (linear) · EMV tag dictionary
Reading
Frequently asked questions
What makes a TLV node constructed?
Bit 6 of the first tag byte. When set, the value is itself a sequence of TLV objects, which is what allows the nesting this tree renders.
Why is a tag shown as hex with no name?
Because it is outside the EMV dictionary — a proprietary or issuer-specific object. The structure still parses; only the label is unknown.
How are multi-byte tags recognised?
When the low five bits of the first byte are all set, the tag continues into further bytes, each signalling continuation in its top bit. That is why EMV has the 9Fxx family.
Why does my tree end early?
A length that overruns the buffer, or a truncated capture. The last complete node marks the point where the encoding stops being consistent.
Does anything I paste leave my browser?
Nothing. The tool is entirely client-side: the page ships a static script, does no network calls, and never transmits what you paste. You can confirm it by opening the network tab, or by loading the page and then going offline.