How do I turn JSON into a Ruby Hash?

Paste the JSON and leave the mode on Hash. The tool renders a Ruby Hash literal directly. For example the input with id 1 and login octocat becomes a Hash like the one with id: 1 and login: "octocat" on its own lines. Nested objects render as nested Hash literals and arrays render as Ruby arrays, indented two spaces per level, so the output drops straight into a .rb file or an irb session without any reshaping.

Should I use symbol keys or string keys?

Use symbol keys for internal Ruby code; they are interned once and compare faster, and Rails params, config and most gems expect them. The shorthand form name: is the everyday choice, while the rocket form :name => value is handy when a key is not a valid label, for instance a key with a dash. Use string keys ("name" => value) when the Hash mirrors external JSON you will re-serialize, or when keys can collide with Ruby reserved words. The tool lets you switch between all three from one dropdown.

What does Struct mode generate?

Struct mode emits Struct.new class definitions and the call that fills them. Input like the object with name and count produces Root = Struct.new(:name, :count, keyword_init: true) followed by Root.new(name: "x", count: 3). With keyword_init turned off you get positional Struct.new(:name, :count) and a positional Root.new("x", 3). Structs give you real attribute readers (root.name) and a defined shape, which a bare Hash does not, so they suit config objects and DTOs.

Does JSON null become nil?

Yes. Every JSON null maps to Ruby nil in both modes, because nil is Ruby's single representation of absence, the way null is JSON's. So the object with company set to null renders company: nil in Hash mode and passes nil into the matching Struct member. A key that is missing entirely from one element of an object array also passes nil, so the folded Struct stays consistent across every element even when their shapes differ.

How are nested objects and arrays of objects handled?

In Hash mode a nested object becomes a nested Hash and an array stays an array, preserving the full tree. In Struct mode each distinct nested object becomes its own Struct named after the key path, so an addr object under the root becomes RootAddr. An array of objects is special: the tool folds every element's keys into one shared Struct, so [{"id":"a"},{"id":"b","note":"x"}] yields a single Struct with both :id and :note, and the element without a note passes note: nil rather than producing two near-duplicate classes.

Is my JSON uploaded anywhere?

No. Parsing with the built-in JSON parser, the type mapping, and the rendering all happen inside this browser tab. Open DevTools and the Network panel and you will see zero requests fire as you paste and convert. The Share link encodes your JSON and options into the URL so a result is reproducible, which means you control what gets shared; if the payload is sensitive, use the Copy button instead of sharing the link. Only your style preferences live in localStorage.

Seed a Rails fixture or test factory from a real payload

You captured an API response in a log and need it as a Ruby Hash in a spec. Paste the JSON, keep symbol keys in shorthand form, copy the output straight into a let block or a FactoryBot trait. null fields come out as nil, nested objects as nested hashes, so the fixture matches the wire shape exactly without you retyping a single brace.

Convert a config.json into a typed Ruby config object

Your service reads a JSON config but you want attribute readers and a fixed shape rather than h["server"]["port"] string-key chains. Switch to Struct mode, name the root Config, and you get Config, ConfigServer and ConfigServerTls Structs plus the instantiation. Now config.server.port is a real method call, type-checked by shape, not a Hash lookup that returns nil on a typo.

Port a JSON snippet into an irb or pry session

You are debugging and want a sample object in the console as a live Ruby value. Paste the JSON, pick the rocket key style if the source uses dashed keys, copy, and paste into pry. The literal evaluates on the spot, so you can poke at it with .dig, .map and .select instead of squinting at raw JSON text.

Build seed data for db:seed from an export

A teammate hands you a JSON export of reference rows. Paste the array of objects, stay in Hash mode with symbol keys, and you get a Ruby array of hashes ready for Model.create!(attrs) in seeds.rb. Keys that one record has and another lacks render explicitly as nil, so every create call gets the same attribute set.

JSON to Ruby Hash and Struct Generator

Paste JSON, get a Ruby Hash literal or Struct.new classes; symbol or string keys, null maps to nil, nested objects, zero upload.

Runs locally
Category Format Converter
Best for Checking file type, size, metadata, and obvious mismatch signals before sharing.

ModeKeys

Examples:

JSON input

Ruby output

How keys, nil and Structs are generated

Hash mode renders the JSON as a Ruby Hash literal: JSON null becomes nil, true/false stay as-is, numbers pass through verbatim, and strings are double-quoted with proper Ruby escapes. Keys can be symbols in shorthand form (name:), classic rocket form (:name => ), or plain string keys ("name" => ) — pick whatever your codebase uses. Struct mode emits Struct.new(:a, :b) class definitions plus the instantiation that fills them; every nested object becomes its own Struct named after the key path, and an array of objects folds all its elements into one shared Struct so a key missing from some elements simply passes nil. Everything runs in your browser; the JSON never reaches a server.

What this tool does

Paste any JSON payload and get back idiomatic Ruby in one of two shapes. Hash mode renders the JSON as a Ruby Hash literal: pick symbol keys in the modern shorthand form (name: value), the classic rocket form (:name => value), or plain string keys ("name" => value), and the tool maps every scalar the way Ruby expects. JSON null becomes nil, true and false stay as true and false, integers and floats pass through verbatim, and strings are double-quoted with correct Ruby escapes so a quote, a newline or an interpolation-looking sequence like the hash brace never breaks the literal. Struct mode generates Struct.new(:a, :b) class definitions plus the instantiation that fills them: every nested object lifts out into its own named Struct, and an array of objects folds all of its elements into one shared Struct so a key present in some elements and missing in others simply passes nil. Rename the root Struct, toggle keyword_init, share the exact input and options as a link, copy the result or download a .rb file. Everything runs in your browser; the JSON you paste never touches a server.

Tool details

Input: Text + Numbers + Structured content; The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
Output: Live result + Copy + Download; The result area focuses on usable output, with copy, download, or preview actions when supported.
Privacy: Browser-side processing; The main tool logic does not call an external API, so inputs normally stay in the current tab.
Save / share: Shareable URL state; Key settings are encoded in the URL so another person can reopen the same setup.
Performance budget: Initial JS <= 9 KB; No WASM budget is declared, keeping the tool quick to open on mobile.
Best fit: Format Converter · Developer; Category and role tags drive related tools, internal links, and quick fit checks.

How to use

1. Input

Paste or drop your content into the tool panel.
2. Process

Click the button. All processing is local in your browser.
3. Copy / Download

Copy the result or download to disk in one click.

How JSON to Ruby fits into your work

Use it before upload, handoff, archive, support review, or any moment where a file needs one local check before it leaves your machine.

File jobs

Checking file type, size, metadata, and obvious mismatch signals before sharing.
Preparing mixed folders for upload, archive, intake, or review.
Keeping sensitive files in the browser instead of sending them to an account-based service.

File checks

Do not treat the extension alone as proof of the real file type.
Review metadata before a file goes to customers, vendors, or a public page.
Keep the original file until the copied, converted, or exported result is verified.

Good next steps

These links move the current task into a more complete workflow.

Real-world use cases

Seed a Rails fixture or test factory from a real payload
You captured an API response in a log and need it as a Ruby Hash in a spec. Paste the JSON, keep symbol keys in shorthand form, copy the output straight into a let block or a FactoryBot trait. null fields come out as nil, nested objects as nested hashes, so the fixture matches the wire shape exactly without you retyping a single brace.
Convert a config.json into a typed Ruby config object
Your service reads a JSON config but you want attribute readers and a fixed shape rather than h["server"]["port"] string-key chains. Switch to Struct mode, name the root Config, and you get Config, ConfigServer and ConfigServerTls Structs plus the instantiation. Now config.server.port is a real method call, type-checked by shape, not a Hash lookup that returns nil on a typo.
Port a JSON snippet into an irb or pry session
You are debugging and want a sample object in the console as a live Ruby value. Paste the JSON, pick the rocket key style if the source uses dashed keys, copy, and paste into pry. The literal evaluates on the spot, so you can poke at it with .dig, .map and .select instead of squinting at raw JSON text.
Build seed data for db:seed from an export
A teammate hands you a JSON export of reference rows. Paste the array of objects, stay in Hash mode with symbol keys, and you get a Ruby array of hashes ready for Model.create!(attrs) in seeds.rb. Keys that one record has and another lacks render explicitly as nil, so every create call gets the same attribute set.

Common pitfalls

Expecting symbol shorthand to work on every key. The shorthand label form is only valid for keys that are legal Ruby labels. For a key like first-name the tool falls back to the quoted symbol form or the rocket arrow form so the output still parses; do not hand-edit it back to a bare label.
Forgetting that Struct positional order follows the JSON key order. With keyword_init off, the new call maps arguments by position, so reordering the JSON keys silently reassigns values. Keep keyword_init on when the source key order is not stable, so each value is bound to its named member.
Treating JSON null and a missing key as different things in Struct mode. Both render as nil, because a folded Struct must fill every member for every element. If the distinction matters to your code, keep the data as a Hash and check key presence with has_key? rather than relying on the Struct.

Privacy

Conversion is plain JavaScript that runs in your browser tab: the built-in JSON parser reads your input, the mapping turns it into Ruby source, and nothing is sent anywhere. There is no logging of the JSON you paste. The one caveat is the Share link, which encodes your input and options in the URL query string, so a link pasted into chat will record those in the recipient server's access log. For a sensitive payload, use the Copy button and paste the Ruby text instead of sharing the URL.

FAQ

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JSON to Ruby Hash and Struct Generator

What this tool does

Tool details

How to use

1. Input

2. Process

3. Copy / Download

How JSON to Ruby fits into your work

File jobs

File checks

Good next steps

Real-world use cases

Seed a Rails fixture or test factory from a real payload

Convert a config.json into a typed Ruby config object

Port a JSON snippet into an irb or pry session

Build seed data for db:seed from an export

Common pitfalls

Privacy

FAQ

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