Is the prototype visualizer free?

Yes. Explore unlimited objects and lookups with no account.

What is the prototype chain?

Every JavaScript object has a hidden link to another object, its prototype. When you read a property, the engine checks the object, then its prototype, then that prototype's prototype, until it finds the property or reaches null.

What is the difference between __proto__ and prototype?

__proto__ is the actual link from an object to its prototype. prototype is a property on constructor functions pointing to the object that will become the __proto__ of instances created with new.

How does property lookup work?

The engine checks own properties first, then walks up the chain hop by hop. A property on the object itself shadows the same-named property anywhere up the chain.

What is hasOwnProperty?

A method that tells you whether a property lives directly on the object (an own property) rather than being inherited from somewhere up the chain.

Does my input leave my browser?

No. Object definitions and chain exploration happen locally.

Prototype Visualizer - Free Online JavaScript Prototype Tool | IconVault

Explore JavaScript prototype chains interactively: define objects, walk property lookups hop by hop, inspect own properties. Free.

All tools

Prototype Visualizer

Walk property lookups hop by hop up the chain

5 of 5 free uses left

Presets

Define objects

Look up a property

Format: object.property, e.g. dog.legs or scores.map

5 of 5 free copies left. Exploring the chain is always free.

Lookup: dog.legs

null

Click any node to inspect its own properties.

dog: Found: "legs" is an OWN property of dog = 3. Lookup stops here.

Hop 1 of 1

Own properties

Select a node above to see what it owns (not inherits).

Your objects

Built-ins included: Object.prototype, Array.prototype, String.prototype, Number.prototype, Function.prototype.

Simplified model: real engines store the link in an internal [[Prototype]] slot and primitives are temporarily boxed. The lookup order shown matches the language spec.

About this tool

IconVault's Prototype Visualizer turns prototypal inheritance into something you can see: define your own objects with presets like Animal and Dog, then walk property lookups hop by hop up the prototype chain. Click any node to inspect its own properties and see exactly where a lookup succeeds or falls through to null.

It shows the difference between __proto__ and prototype, how constructors link to instances, and why property shadowing works. Built for students and anyone who has ever been confused by JavaScript inheritance. Free and runs fully in your browser.

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Prototype Visualizer - Free Online JavaScript Prototype Tool | IconVault

Prototype Visualizer

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