Record-path selection
Candidate arrays are listed so you can decide which level represents spreadsheet rows.
Nested JSON conversion without silent number rounding
JSON to Excel Converter for Nested Data and Long IDs
Convert JSON to XLSX locally with record-path selection, explicit array strategies, flattened field previews, duplicate-key checks, and lossless handling for long numeric IDs.
✓ Runs locally✓ No account✓ Free first release
Start with the exampleLocal browser processingYour file contents are not uploaded.
10 MB · 50,000 row limitConversion workbench
Inspect first. Export second.
Source structure, quality findings, and every deliberate transformation stay visible before download.
1
Source data
Paste JSON or upload a JSON file
or drop it here
2
Structure choices
Nothing ambiguous is hidden behind “auto.”
3
Preview and quality report
Analyze the sample or your own data to continue.
Your source data is still only in this browser.
Analysis creates a table preview, a ranked issue list, and an exact transformation summary.
Private by design
Source bytes remain in this browser tab.
Reviewable
Preview values and risks before export.
Traceable
Download a JSON conversion report.
What the converter checks
Quality findings belong beside the output
A successful parse is not proof that the result kept the source meaning. These checks surface the places where tabular conversion can change or hide data.
Lossless numeric parsing
The original JSON number text is retained. Unsafe or 16+ digit values are written as XLSX text cells.
Explicit array handling
Keep arrays as JSON, join scalar arrays, or expand one selected array—never an automatic multi-array cross product.
Path and duplicate-key checks
Literal dotted keys stay distinct from nested paths, and duplicate JSON object keys block conversion.
Preservation rules
Know what happens to difficult values
The tool records deliberate changes and keeps ambiguous structures visible rather than silently normalizing them.
Read the full check definitions →Source featureConverter behavior
Long integer IDs
Original digits are preserved and written as text cells when numeric precision is unsafe.
Nested objects
Flattened into escaped path columns such as profile.name.
Nested arrays
Stored as JSON text by default; alternative handling is always explicit.
Missing fields
Shown as missing cells and counted, rather than confused with source empty strings.
A short, inspectable workflow
From source to checked XLSX
- 1
Add the JSON
Paste a document or choose a local JSON file. Parsing stays inside the browser.
- 2
Choose rows and arrays
Confirm the record path and how any nested array should be represented.
- 3
Inspect and download XLSX
Review types, missing fields, and transformations before creating the workbook.
A concrete failure mode
Why native JSON parsing can damage a customer ID
A 19-digit integer can be rounded before an exporter sees it. DataFormatKit validates duplicate keys, reads the source number text, and writes unsafe identifiers as Excel text cells so the workbook keeps every digit.
Inspect the included example