CSV to XLSX Converter — Fast & Free Online

Converting CSV to XLSX imports comma-separated plain text into an Excel spreadsheet, adding the formatting, column structure, and formula capabilities that CSV cannot store. CSV contains raw tabular data as plain text with one record per line and field values delimited by commas; XLSX stores cells in an XML-based structure with defined column widths, number formatting, and optionally applied styles. During import, the converter detects column data types — numbers, dates, and text — and assigns the appropriate cell format in the XLSX output. Columns containing date strings in ISO 8601 or locale-specific formats are converted to Excel date serial numbers with a date display format applied. Leading zeros in fields such as postal codes are preserved only if the column is formatted as text. 1converter uses LibreOffice Calc in headless mode to perform this conversion, applying auto-detection of delimiter characters (comma, semicolon, or tab) and UTF-8 encoding for the input CSV.