JSON vs XLS
A detailed comparison of JSON Data and Excel Spreadsheet (Legacy) — file size, quality, compatibility, and which format to choose for your workflow.
JSON Data
Documents & TextJSON (JavaScript Object Notation) is a lightweight data interchange format that is human-readable and easy for machines to parse and generate. It has become the dominant format for web APIs, configuration files, and structured data exchange.
About JSON filesExcel Spreadsheet (Legacy)
Spreadsheets & DataXLS is the legacy binary format for Microsoft Excel 97-2003 spreadsheets. While superseded by XLSX, it remains common in archived data and older business systems.
About XLS filesStrengths Comparison
JSON Strengths
- Dead-simple — you can memorize the entire grammar on one page.
- Native parsers in every programming language.
- Human-readable and easy to debug.
- Compact — much smaller than equivalent XML.
- Frozen spec — a JSON parser written in 2010 still handles new JSON files from 2026.
XLS Strengths
- Universal legacy — every Excel since 1997 opens .xls natively.
- Binary format is compact and loads quickly.
- Full support for formulas, charts, pivots, and VBA macros.
- Deep integration with every accounting and ERP system of the 1990s-2000s.
Limitations
JSON Limitations
- No comments allowed — config files feel verbose.
- No trailing commas — a constant source of parse errors.
- No native date, decimal, or binary types — everything is strings or numbers.
- Easily bloated by repeated keys; large payloads compress poorly vs binary alternatives.
- Streaming is awkward — JSON wants to be parsed whole.
XLS Limitations
- Row/column limits are ~64× smaller than modern XLSX.
- Macro-enabled variants are a notorious malware vector.
- Binary corruption often means total data loss.
- Cannot represent modern Excel features (dynamic arrays, LAMBDA, structured references).
- Microsoft stopped evolving the format in 2007.
Technical Specifications
| Specification | JSON | XLS |
|---|---|---|
| MIME type | application/json | application/vnd.ms-excel |
| Extension | .json | — |
| Standard | ECMA-404, RFC 8259 | — |
| Encoding | UTF-8, UTF-16, or UTF-32 | — |
| Allowed types | object, array, string, number, boolean, null | — |
| Max rows | — | 65 536 (Excel 97-2003) |
| Max columns | — | 256 (A to IV) |
| Container | — | OLE Compound File |
| Successor | — | .xlsx (2007) |
Typical File Sizes
JSON
- Small config < 1 KB
- REST API payload 1-100 KB
- Database export 10 MB - 100 GB
XLS
- Simple budget (1 sheet) 30-60 KB
- Multi-sheet financial model 500 KB - 5 MB
- Data export with 65 000 rows 5-20 MB
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Frequently Asked Questions
JSON (JavaScript Object Notation) is a lightweight text format for data exchange, popularized by Douglas Crockford around 2001. JSON represents nested objects, arrays, strings, numbers, booleans, and null values in a syntax derived from JavaScript. It is the default data format for modern web APIs.
JSON files are plain text — open them in any text editor (Notepad, VS Code, Sublime Text, TextEdit). For formatted reading, use JSON-aware editors (VS Code auto-indents) or online viewers like jsonformatter.org. Every web browser displays JSON directly if you open the file locally.
Use KaijuConverter's JSON-to-CSV converter for nested data flattened into a tabular format. For simple flat JSON (array of objects), command-line tools like jq + csvkit give more control. Python's pandas and JavaScript's PapaParse also handle the conversion in one line of code.
JSON for machine-to-machine data exchange (APIs, config) — strict spec, fast parsers in every language. YAML for human-edited config files — supports comments, multi-line strings, and references. Kubernetes, Docker Compose, and GitHub Actions use YAML; REST APIs overwhelmingly use JSON.
JSON's strict specification disallows comments to keep parsers simple and unambiguous. Workarounds include JSONC (JSON with Comments, used by VS Code config), JSON5 (relaxed syntax with comments), or a convention of adding a "comment" or "_doc" field in your data.
JSON itself cannot execute code like JavaScript eval() can, making it safer than older exchange formats. However, deeply nested JSON can exhaust memory (a "billion laughs" variant) — use streaming parsers and limit recursion depth when processing untrusted input.