XLSX, CSV or JSON? Spreadsheet formats compared

XLSX – the format for daily work

XLSX is the modern Excel format. It stores not only values but also data types, multiple sheets, formatting and formulas. For editing by humans it is the first choice: numbers stay numbers, dates stay dates, and postcodes keep their leading zero.

The downside: XLSX is a complex, packed format. Programs that only want to read simple data often struggle with it – there CSV is the better choice.

CSV – the lowest common denominator

CSV is a simple text file: one line per record, columns separated by a delimiter. Almost every program in the world can read and write CSV – from online shops to databases to statistics software. That makes CSV the universal exchange format.

The price of simplicity: CSV stores no data types, no formatting and only a single table. Without agreement on delimiter and character set, misunderstandings arise easily.

JSON – the language of interfaces

JSON is the standard format for exchanging data between programs, especially over web APIs. It can represent nested structures that go far beyond a flat table. For developers and automation it is ideal, but for direct editing by humans it is unwieldy.

HTML – tables for display

An HTML table is meant for display in the browser or embedding in a web page. It is not an editing but a presentation format. Handy when you want to publish data quickly or embed it in a document without the recipient needing a spreadsheet program.

Which format for what? A rule of thumb

The choice is simpler than it sounds – go by the goal:

• Edit yourself or send to colleagues: XLSX.
• Import into another program, shop or database: CSV.
• Exchange with an interface or a script: JSON.
• Display or embed on a web page: HTML.

Switching between formats

You are never locked into one format. With the SmashDash spreadsheet converter you switch between XLSX, CSV, JSON and HTML – locally in the browser, no upload. That way you bring the same data into exactly the shape each target expects.

Frequently asked questions

Which is better, CSV or XLSX? It depends on the purpose. XLSX is better for editing and preserving data types, CSV better for universal import into other programs.

When should I use JSON? Whenever data is exchanged between programs or over an API – especially with nested structures. To analyse it, convert JSON to Excel.

Can I switch between formats at any time? Yes. The converter converts between XLSX, CSV, JSON and HTML. Just note that CSV and JSON store no Excel formatting.

All SmashDash tools at a glance

SmashDash brings five free spreadsheet tools together in one place – each runs entirely in the browser, with no upload and no account:

• Turn Excel and CSV into interactive, filterable charts. – Turn Excel and CSV into interactive, filterable charts.
• Design charts with your own values and export them as SVG or HTML. – Design charts with your own values and export them as SVG or HTML.
• Convert Excel, CSV and JSON into XLSX, CSV, JSON, Markdown or HTML. – Convert Excel, CSV and JSON into XLSX, CSV, JSON, Markdown or HTML.
• Remove duplicates and empty rows, normalise number formats. – Remove duplicates and empty rows, normalise number formats.
• Merge, split and compress PDFs and extract tables. – Merge, split and compress PDFs and extract tables.

All processing happens locally in your browser – your files are never uploaded, fully privacy-friendly.