Select JSON, YAML, or CSV as the source and a different format as the target. The workspace never guesses a format or creates data-bearing URLs, and if you set both dropdowns to the same format the other side flips automatically, because a conversion where source equals target is refused rather than silently echoed back.
02
Paste and validate immediately
Pasting converts at once; ordinary edits re-run after a short pause while Auto-convert is on, and Ctrl or Command plus Enter runs on demand. Syntax errors appear with a line and column whenever the parser provides them, and Load sample fills the field with a small valid document in the selected source format so you can see a clean conversion first.
03
Set the output options
For JSON and YAML targets, the Output indent control chooses two or four spaces. When CSV is the target, that control becomes the spreadsheet-safe toggle — on by default — which prefixes any cell beginning with =, +, -, or @ with an apostrophe so spreadsheet applications do not execute it as a formula.
04
Review fidelity warnings
Warnings call out every accepted loss: YAML anchors expanded, YAML comments removed, CSV cells treated as strings, nulls written as empty cells, and formula-like values escaped. Unsupported or ambiguous structures — YAML merge keys, custom tags, multiple documents, oversized integers, or nested values headed for CSV — stop the conversion with a named error instead of changing meaning silently.
05
Copy, download, or reverse
Copy the validated result to the clipboard, download it as toolars-converted with the matching .json, .yaml, or .csv extension, or use Swap formats to feed the current output back as the next source — the quick way to confirm a JSON to YAML to JSON round trip preserves the data.
06
Continue with this result
Open a fresh workspace below with a copy of this result. Nothing is sent or saved; run the next tool when ready. One follow-up at a time. Close it before opening another. Changing the source result, leaving or refreshing this page, or 10 minutes after opening clears the follow-up and its edits. The source stays here.
Tool facts
Processing
In your browser
Input leaves this device
Never
Retention
Optional local handoff
Price
Free
Your input stays in the browser.
Structured Data Converter uses its verified local execution path and does not create a hidden input or output history.
Local execution
Runs inside the current browser tab.
No hidden processing
Active tool data never becomes a Toolars document record.
No account required
Use the core workflow without creating a profile. Favorites sync to your account after you sign in.
Workspace and handoff
Closing the tab clears normal workspace data. If you choose a handoff, the selected result stays on this device across reloads and tab closes, and can be accepted for 30 minutes. Accepting or dismissing removes it; expired records are cleared the next time the handoff feature is used.
When Structured Data Converter is useful
Turn commented YAML into strict JSON
Paste a configuration file that uses anchors and comments, convert YAML to JSON with two-space indent, and read the warnings: comments are dropped and anchors expanded, so review the output before it becomes a test fixture.
Export a user list as spreadsheet-safe CSV
Convert a flat JSON array of user records to CSV with the spreadsheet-safe toggle on, so a cell starting with = arrives escaped and cannot execute as a formula when the file is opened in a spreadsheet application.
Verify a round trip before shipping
Convert JSON to YAML, press Swap formats, and convert back: if the restored document matches the source, the intermediate format is lossless for your data shape and safe to hand to another team.
What Structured Data Converter actually does
A microservice's example configuration ships as commented YAML with anchors, the integration tests want the same data as strict JSON, and the support team wants the user list as a spreadsheet-ready CSV. A free structured data converter online should handle all three without sending the document anywhere. This structured data converter online converts JSON, YAML, and CSV in the browser as you paste: syntax errors arrive with line and column, warnings name every accepted loss — comments dropped, anchors expanded, CSV cells read as strings — and formula-like cells are escaped before a spreadsheet can execute them. Use it to draft a config in YAML and hand JSON to the API, to flatten a JSON array into a CSV import, or to verify that a YAML round trip preserves your data before another team depends on it. The limits stay explicit: 256 KiB of input, 40 levels of nesting, and only a flat array of objects becomes CSV. Because nothing is uploaded, configurations carrying tokens and internal endpoints stay on the device.
Common questions
Which formats are supported?
The workspace supports JSON, YAML 1.2 core syntax, and comma-delimited CSV with a required unique header row. TOML and XML still require separate fidelity work and are not accepted in this release, and choosing the same format on both sides is refused — every run converts between two different formats.
How is YAML handled safely?
In text mode, parsing runs in a disposable Web Worker with hard limits: 256 KiB of input, 40 levels of nesting, 10,000 nodes, 50 alias expansions, and a 1,500 ms time budget. Custom or executable tags, merge keys, remote schemas, DTDs, imports, includes, and all network resource loading are disabled, so a hostile or malformed document cannot reach outside the parser.
What can change during conversion?
JSON cannot represent YAML comments or anchor identity, and CSV cannot preserve scalar types, null identity, or nested structures. Each accepted loss is surfaced as a warning on the result; unsafe or ambiguous shapes are rejected outright. Duplicate keys, properties named __proto__, constructor, or prototype, non-finite numbers, and integers beyond the safe range are refused rather than coerced.
What does the spreadsheet-safe CSV option do?
When the target is CSV and the toggle is on, any cell whose text begins with =, +, -, or @ — after leading spaces or tabs — is prefixed with an apostrophe, so spreadsheet applications display it as text instead of executing it as a formula. Each affected run adds a warning so the change is visible. Leave it on for files headed to a spreadsheet; turn it off only when the CSV feeds a system that expects the raw values.
Why was my CSV rejected?
In text mode, the parser requires a header row whose names are non-empty and unique — a leading byte-order mark on the first header is tolerated — and every record must have exactly as many fields as the header. Quoted fields follow the standard rules: double quotes escape as doubled quotes and may contain newlines, but a quote in the middle of an unquoted field is an error with its line and column. Output is limited to 5,000 rows and 256 columns, and only a flat array of objects with identical keys converts to CSV.
Are my values uploaded or saved?
Conversion runs locally. The current document and same-page follow-up stay in memory; Clear removes the current document. Source data and results are not sent through URLs, analytics, logs or feedback forms. Cross-tool file handoff is a separate, optional action. If you explicitly hand output to another tool, that output is saved in local browser storage. Resetting, reloading or closing the workspace does not remove this pending copy. Receiving or dismissing the handoff deletes it; after 30 minutes it can no longer be received.
What are the CSV file mode limits?
File mode supports explicit UTF-8, UTF-16LE/BE, GB18030 or Windows-1252 and comma, semicolon, tab or pipe separators. Column names are preserved unless trimming is selected; names must be unique and nonblank. Input ≤ 100 MiB, output ≤ 32 MiB, ≤ 256 columns and ≤ 1 MiB per decoded record measured as UTF-8. The preview shows 20 rows with cells shortened to 160 characters; downloads retain full values. JSONL stores strings. Normalized CSV uses UTF-8, commas, CRLF and quoted fields; an optional BOM helps encoding recognition but does not enforce types. Empty physical records are skipped. Quoting and encoding are normalized, not byte-for-byte preserved. Processing is local and cancellable; output stays in memory, so peak memory can exceed 32 MiB.
When should I use JSON, YAML, or CSV?
Use JSON when machines exchange data: APIs, configuration consumed by code, and test fixtures that must stay unambiguous. Use YAML for files people edit by hand — deployment manifests and documentation — where comments and anchors help. Use CSV when a spreadsheet or a data import expects rows and columns. Convert between them here, and let the warnings tell you what the target format cannot keep.
What is the difference between JSON and XML?
JSON is a minimal data format built on objects and arrays: no closing tags, no attributes, and one canonical way to write most values, which makes it smaller and easier to parse in JavaScript and most modern APIs. XML is a document format with elements, attributes, namespaces, and schemas, and it still rules industries that validate documents, such as publishing, banking standards, and many enterprise integrations. This workspace converts JSON, YAML, and CSV; XML needs a document-aware converter because its attribute and namespace model does not map one-to-one onto plain data trees.
