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Spreadsheets Without Excel: XLSX, CSV, JSON and SQL Conversions
8 min read
Tabular data rarely stays in one format. A client sends a workbook, your analytics platform exports CSV, your database dumps JSON or SQL, and you need to merge it all into one place. Format conversion is a daily task for analysts, developers, marketers and administrators — and it is also a task where data often contains private or commercially sensitive rows. This guide explains the four formats, when to use each, and how to convert safely.
The four formats at a glance
| Format | What it is | Best for | Watch out for |
|---|---|---|---|
| XLSX | Excel workbook (zip of XML) | Formulas, multiple sheets, formats | Binary; not readable as text |
| CSV | Comma-separated plain text | Exports, imports, tiny files | No types, no formulas, quoting rules |
| JSON | Nested object structure | APIs, web apps, flexible data | No columns — nesting is deeper |
| SQL | INSERT statements / schema | Populating databases | Empty values and quoting need care |
The golden rule: choose the destination format by what will consume the data. If a human opens it in Excel, produce XLSX or CSV. If an API consumes it, produce JSON. If a database imports it, produce SQL. Converting to a format the receiver can't use is as bad as not converting at all.
CSV: the universal exchange format
CSV (comma-separated values) is plain text, which makes it the most portable tabular format: any spreadsheet, database or script can read it. The trade-offs are real, though. CSV has no data types — a value like 00123 is a number or a string depending on the reader — and no formulas or multiple sheets. Export tools usually must quote fields containing commas, quotes or newlines, and the quoting convention varies by region (semicolon-separated in some locales). For simple rectangular tables, CSV is still the fastest path between two systems.
JSON: nested and structured
JSON is the native format of the web — every API and almost every JavaScript application works with it. Unlike a spreadsheet grid, JSON can represent nested structures: an order with line items, a user with an address object, a tree of categories. When you export XLSX to JSON, these shapes are flattened into rows of key/value pairs, which is exactly right for feeding data into web applications, dashboards and migration scripts.
SQL: straight into the database
Converting a spreadsheet to SQL produces INSERT statements (and optionally a table definition) that load your data into a relational database. This is the path for bootstrap data, seed scripts, and moving flat files into PostgreSQL, MySQL or SQLite. Values are quoted and escaped correctly, so strings with apostrophes and NULL cells are handled the way the database expects. You get the column order right once, and the schema work is done.
XLSX: the workbook format
XLSX is the modern Excel format: a zip archive containing XML sheets, so real workbooks can carry multiple worksheets, formulas, number formats and styling. Reading and writing XLSX is what most 'excel-style' tools offer. When you convert XLSX to CSV or JSON, each worksheet typically becomes its own file — the sheet boundary is preserved as a file boundary.
Converting without exposing your data
Spreadsheet data is almost always sensitive: payroll tables, customer lists, inventory prices, internal reports. Uploading it to an online converter to read a client's workbook means your business data is passing through someone else's server. Conversion in the browser reads the file locally, parses every cell, and writes the new format — on your own machine.
Spreadsheet tools in Convrs
- XLSX to CSV exports sheets as plain-text tables.
- XLSX to JSON produces structured objects for web apps.
- CSV to SQL generates valid INSERT statements.
Each operates fully client-side, so customer and financial data can change format without ever leaving the browser.